Implementing IPv6 Addressing and Basic Connectivity

Implementing basic IPv6 connectivity in the Cisco IOS software consists of assigning IPv6 addresses to individual router interfaces. The forwarding of IPv6 traffic can be enabled globally, and Cisco Express Forwarding switching for IPv6 can also be enabled. Basic connectivity can be enhanced by configuring support for AAAA record types in the Domain Name System (DNS) name-to-address and address-to-name lookup processes, and by managing IPv6 neighbor discovery.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tooland the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Prerequisites for Implementing IPv6 Addressing and Basic Connectivity

  • The following prerequisites apply to Cisco Express Forwarding and distributed Cisco Express Forwarding for IPv6:
    • To forward IPv6 traffic using Cisco Express Forwarding or distributed Cisco Express Forwarding, you must configure forwarding of IPv6 unicast datagrams globally on the router by using the ipv6 unicast-routing command, and you must configure an IPv6 address on an interface by using the ipv6 address command.
    • You must enable Cisco Express Forwarding for IPv4 globally on the router by using the ip cef command before enabling Cisco Express Forwarding for IPv6 globally on the router by using the ipv6 cef command.
    • On distributed architecture platforms that support both Cisco Express Forwarding and distributed Cisco Express Forwarding, you must enable distributed Cisco Express Forwarding for IPv4 globally on the router by using the ip cef distributed command before enabling distributed Cisco Express Forwarding for IPv6 globally on the router by using the ipv6 cef distributed command.
    • To use Unicast Reverse Path Forwarding (RPF), enable Cisco Express Forwarding switching or distributed Cisco Express Forwarding switching in the router. There is no need to configure the input interface for Cisco Express Forwarding switching. As long as Cisco Express Forwarding is running on the router, individual interfaces can be configured with other switching modes.

      Note

      For Unicast RPF to work, Cisco Express Forwarding must be configured globally in the router. Unicast RPF will not work without Cisco Express Forwarding.


Restrictions for Implementing IPv6 Addressing and Basic Connectivity

  • Multiple IPv6 global addresses within the same prefix can be configured on an interface; however, multiple IPv6 link-local addresses on an interface are not supported.

  • IPv4 alias and IPv6 alias addresses used must be available in the global routing table and not under VRF.

Information About Implementing IPv6 Addressing and Basic Connectivity

IPv6 for Cisco Software

IPv6, formerly named IPng (next generation), is the latest version of the Internet Protocol (IP). IP is a packet-based protocol used to exchange data, voice, and video traffic over digital networks. IPv6 was proposed when it became clear that the 32-bit addressing scheme of IP version 4 (IPv4) was inadequate to meet the demands of Internet growth. After extensive discussion it was decided to base IPng on IP but add a much larger address space and improvements such as a simplified main header and extension headers. IPv6 is described initially in RFC 2460, Internet Protocol, Version 6 (IPv6) Specification, issued by the Internet Engineering Task Force (IETF). Further RFCs describe the architecture and services supported by IPv6.

The architecture of IPv6 has been designed to allow existing IPv4 users to transition easily to IPv6 while providing services such as end-to-end security, quality of service (QoS), and globally unique addresses. The larger IPv6 address space allows networks to scale and provide global reachability. The simplified IPv6 packet header format handles packets more efficiently. IPv6 prefix aggregation, simplified network renumbering, and IPv6 site multihoming capabilities provide an IPv6 addressing hierarchy that allows for more efficient routing. IPv6 supports widely deployed routing protocols such as Routing Information Protocol (RIP), Integrated Intermediate System-to-Intermediate System (IS-IS), Open Shortest Path First (OSPF) for IPv6, and multiprotocol Border Gateway Protocol (BGP). Other available features include stateless autoconfiguration and an increased number of multicast addresses.

Large IPv6 Address Space for Unique Addresses

The primary motivation for IPv6 is the need to meet the demand for globally unique IP addresses. IPv6 quadruples the number of network address bits from 32 bits (in IPv4) to 128 bits, which provides more than enough globally unique IP addresses for every networked device on the planet. By being globally unique, IPv6 addresses inherently enable global reachability and end-to-end security for networked devices, functionality that is crucial to the applications and services that are driving the demand for the addresses. Additionally, the flexibility of the IPv6 address space reduces the need for private addresses; therefore, IPv6 enables new application protocols that do not require special processing by border devices at the edge of networks.

IPv6 Address Formats

IPv6 addresses are represented as a series of 16-bit hexadecimal fields separated by colons (:) in the format: x:x:x:x:x:x:x:x. Following are two examples of IPv6 addresses:

2001:DB8:7654:3210:FEDC:BA98:7654:3210

2001:DB8:0:0:8:800:200C:417A

IPv6 addresses commonly contain successive hexadecimal fields of zeros. Two colons (::) may be used to compress successive hexadecimal fields of zeros at the beginning, middle, or end of an IPv6 address (the colons represent successive hexadecimal fields of zeros). The table below lists compressed IPv6 address formats.

A double colon may be used as part of the ipv6-address argument when consecutive 16-bit values are denoted as zero. You can configure multiple IPv6 addresses per interfaces, but only one link-local address.


Note

Two colons (::) can be used only once in an IPv6 address to represent the longest successive hexadecimal fields of zeros. The hexadecimal letters in IPv6 addresses are not case-sensitive.


Table 1. Compressed IPv6 Address Formats

IPv6 Address Type

Preferred Format

Compressed Format

Unicast

2001:0:0:0:DB8:800:200C:417A

2001::DB8:800:200C:417A

Multicast

FF01:0:0:0:0:0:0:101

FF01::101

Loopback

0:0:0:0:0:0:0:1

::1

Unspecified

0:0:0:0:0:0:0:0

::

The loopback address listed in the table above may be used by a node to send an IPv6 packet to itself. The loopback address in IPv6 functions the same as the loopback address in IPv4 (127.0.0.1).


Note

The IPv6 loopback address cannot be assigned to a physical interface. A packet that has the IPv6 loopback address as its source or destination address must remain within the node that created the packet. IPv6 devices do not forward packets that have the IPv6 loopback address as their source or destination address.


The unspecified address listed in the table above indicates the absence of an IPv6 address. For example, a newly initialized node on an IPv6 network may use the unspecified address as the source address in its packets until it receives its IPv6 address.


Note

The IPv6 unspecified address cannot be assigned to an interface. The unspecified IPv6 addresses must not be used as destination addresses in IPv6 packets or the IPv6 routing header.


An IPv6 address prefix, in the format ipv6-prefix /prefix-length , can be used to represent bit-wise contiguous blocks of the entire address space. The ipv6-prefix must be in the form documented in RFC 2373 where the address is specified in hexadecimal using 16-bit values between colons. The prefix length is a decimal value that indicates how many of the high-order contiguous bits of the address comprise the prefix (the network portion of the address). For example, 2001:DB8:8086:6502::/32 is a valid IPv6 prefix.

IPv6 Address Type: Unicast

An IPv6 unicast address is an identifier for a single interface, on a single node. A packet that is sent to a unicast address is delivered to the interface identified by that address. Cisco software supports the IPv6 unicast address types described in the following sections.

Aggregatable Global Address

An aggregatable global address is an IPv6 address from the aggregatable global unicast prefix. The structure of aggregatable global unicast addresses enables strict aggregation of routing prefixes that limits the number of routing table entries in the global routing table. Aggregatable global addresses are used on links that are aggregated upward through organizations, and eventually to the Internet service providers (ISPs).

Aggregatable global IPv6 addresses are defined by a global routing prefix, a subnet ID, and an interface ID. Except for addresses that start with binary 000, all global unicast addresses have a 64-bit interface ID. The IPv6 global unicast address allocation uses the range of addresses that start with binary value 001 (2000::/3). The figure below shows the structure of an aggregatable global address.

Figure 1. Aggregatable Global Address Format

Addresses with a prefix of 2000::/3 (001) through E000::/3 (111) are required to have 64-bit interface identifiers in the extended universal identifier (EUI)-64 format. The Internet Assigned Numbers Authority (IANA) allocates the IPv6 address space in the range of 2000::/16 to regional registries.

The aggregatable global address typically consists of a 48-bit global routing prefix and a 16-bit subnet ID or Site-Level Aggregator (SLA). In the IPv6 aggregatable global unicast address format document (RFC 2374), the global routing prefix included two other hierarchically structured fields named Top-Level Aggregator (TLA) and Next-Level Aggregator (NLA). The IETF decided to remove the TLS and NLA fields from the RFCs because these fields are policy-based. Some existing IPv6 networks deployed before the change might still be using networks based on the older architecture.

A 16-bit subnet field called the subnet ID could be used by individual organizations to create their own local addressing hierarchy and to identify subnets. A subnet ID is similar to a subnet in IPv4, except that an organization with an IPv6 subnet ID can support up to 65,535 individual subnets.

An interface ID is used to identify interfaces on a link. The interface ID must be unique to the link. It may also be unique over a broader scope. In many cases, an interface ID will be the same as or based on the link-layer address of an interface. Interface IDs used in aggregatable global unicast and other IPv6 address types must be 64 bits long and constructed in the modified EUI-64 format.

Interface IDs are constructed in the modified EUI-64 format in one of the following ways:

  • For all IEEE 802 interface types (for example, FDDI interfaces), the first three octets (24 bits) are taken from the Organizationally Unique Identifier (OUI) of the 48-bit link-layer address (the Media Access Control [MAC] address) of the interface, the fourth and fifth octets (16 bits) are a fixed hexadecimal value of FFFE, and the last three octets (24 bits) are taken from the last three octets of the MAC address. The construction of the interface ID is completed by setting the Universal/Local (U/L) bit--the seventh bit of the first octet--to a value of 0 or 1. A value of 0 indicates a locally administered identifier; a value of 1 indicates a globally unique IPv6 interface identifier.

  • For all other interface types (for example, serial, loopback, ATM, Frame Relay, and tunnel interface types--except tunnel interfaces used with IPv6 overlay tunnels), the interface ID is constructed in the same way as the interface ID for IEEE 802 interface types; however, the first MAC address from the pool of MAC addresses in the router is used to construct the identifier (because the interface does not have a MAC address).

  • For tunnel interface types that are used with IPv6 overlay tunnels, the interface ID is the IPv4 address assigned to the tunnel interface with all zeros in the high-order 32 bits of the identifier.


Note

For interfaces using Point-to-Point Protocol (PPP), given that the interfaces at both ends of the connection might have the same MAC address, the interface identifiers used at both ends of the connection are negotiated (picked randomly and, if necessary, reconstructed) until both identifiers are unique. The first MAC address in the router is used to construct the identifier for interfaces using PPP.


If no IEEE 802 interface types are in the router, link-local IPv6 addresses are generated on the interfaces in the router in the following sequence:

  1. The router is queried for MAC addresses (from the pool of MAC addresses in the router).

  2. If no MAC addresses are available in the router, the serial number of the router is used to form the link-local addresses.

  3. If the serial number of the router cannot be used to form the link-local addresses, the router uses a message digest algorithm 5 (MD5) hash to determine the MAC address of the router from the hostname of the router.

Link-Local Address

A link-local address is an IPv6 unicast address that can be automatically configured on any interface using the link-local prefix FE80::/10 (1111 1110 10) and the interface identifier in the modified EUI-64 format. Link-local addresses are used in the neighbor discovery protocol and the stateless autoconfiguration process. Nodes on a local link can use link-local addresses to communicate; the nodes do not need globally unique addresses to communicate. The figure below shows the structure of a link-local address.

IPv6 devices must not forward packets that have link-local source or destination addresses to other links.

Figure 2. Link-Local Address Format

IPv4-Compatible IPv6 Address

An IPv4-compatible IPv6 address is an IPv6 unicast address that has zeros in the high-order 96 bits of the address and an IPv4 address in the low-order 32 bits of the address. The format of an IPv4-compatible IPv6 address is 0:0:0:0:0:0:A.B.C.D or ::A.B.C.D. The entire 128-bit IPv4-compatible IPv6 address is used as the IPv6 address of a node and the IPv4 address embedded in the low-order 32 bits is used as the IPv4 address of the node. IPv4-compatible IPv6 addresses are assigned to nodes that support both the IPv4 and IPv6 protocol stacks and are used in automatic tunnels. The figure below shows the structure of an IPv4-compatible IPv6 address and a few acceptable formats for the address.

Figure 3. IPv4-Compatible IPv6 Address Format

IPv6 Address Type Multicast

An IPv6 multicast address is an IPv6 address that has a prefix of FF00::/8 (1111 1111). An IPv6 multicast address is an identifier for a set of interfaces that typically belong to different nodes. A packet sent to a multicast address is delivered to all interfaces identified by the multicast address. The second octet following the prefix defines the lifetime and scope of the multicast address. A permanent multicast address has a lifetime parameter equal to 0; a temporary multicast address has a lifetime parameter equal to 1. A multicast address that has the scope of a node, link, site, or organization, or a global scope has a scope parameter of 1, 2, 5, 8, or E, respectively. For example, a multicast address with the prefix FF02::/16 is a permanent multicast address with a link scope. The figure below shows the format of the IPv6 multicast address.

Figure 4. IPv6 Multicast Address Format

An IPv6 address must be configured on an interface for the interface to forward IPv6 traffic. Configuring a global IPv6 address on an interface automatically configures a link-local address and activates IPv6 for that interface. Additionally, the configured interface automatically joins the following required multicast groups for that link:

  • Solicited-node multicast group FF02:0:0:0:0:1:FF00::/104 for each unicast address assigned to the interface

  • All-nodes link-local multicast group FF02::1

  • All-routers link-local multicast group FF02::2


Note

The solicited-node multicast address is used in the Neighbor Discovery process.


The solicited-node multicast address is a multicast group that corresponds to an IPv6 unicast address. IPv6 nodes must join the associated solicited-node multicast group for every unicast address to which it is assigned. The IPv6 solicited-node multicast address has the prefix FF02:0:0:0:0:1:FF00:0000/104 concatenated with the 24 low-order bits of a corresponding IPv6 unicast address (see the figure below). For example, the solicited-node multicast address corresponding to the IPv6 address 2037::01:800:200E:8C6C is FF02::1:FF0E:8C6C. Solicited-node addresses are used in neighbor solicitation messages.

Figure 5. IPv6 Solicited-Node Multicast Address Format

Note

There are no broadcast addresses in IPv6. IPv6 multicast addresses are used instead of broadcast addresses.


IPv6 Address Output Display

When IPv6 or IPv4 command output displays an IPv6 address, a long IPv6 address can overflow into neighboring fields, causing the output to be difficult to read. The output fields were designed to work with the longest possible IPv4 address, which has 15 characters; IPv6 addresses can be up to 39 characters long. The following scheme has been adopted in IPv4 and IPv6 commands to allow the appropriate length of IPv6 address to be displayed and move the following fields to the next line, if necessary. The fields that are moved are kept in alignment with the header row.

The following example displays eight connections. The first six connections feature IPv6 addresses; the last two connections feature IPv4 addresses.


Device# where
Conn Host                Address             Byte  Idle Conn Name
   1 test5               2001:DB8:3333:4::5    6    24 test5
   2 test4               2001:DB8:3333:44::5
                                               6    24 test4
   3 2001:DB8:3333:4::5 2001:DB8:3333:4::5     6    24 2001:DB8:3333:4::5
   4 2001:DB8:3333:44::5
                         2001:DB8:3333:44::5
                                               6    23 2001:DB8:3333:44::5
   5 2001:DB8:3000:4000:5000:6000:7000:8001
                         2001:DB8:3000:4000:5000:6000:7000:8001
                                               6    20 2001:DB8:3000:4000:5000:6000:
   6 2001:DB8:1::1      2001:DB8:1::1          0     1 2001:DB8:1::1
   7 10.1.9.1            10.1.9.1              0     0 10.1.9.1
   8 10.222.111.222      10.222.111.222        0     0 10.222.111.222

Connection 1 contains an IPv6 address that uses the maximum address length in the address field. Connection 2 shows the IPv6 address overflowing the address field and the following fields moved to the next line, but in alignment with the appropriate headers. Connection 3 contains an IPv6 address that fills the maximum length of the hostname and address fields without wrapping any lines. Connection 4 shows the effect of both the hostname and address fields containing a long IPv6 address. The output is shown over three lines keeping the correct heading alignment. Connection 5 displays a similar effect as connection 4 with a very long IPv6 address in the hostname and address fields. Note that the connection name field is actually truncated. Connection 6 displays a very short IPv6 address that does not require any change in the display. Connections 7 and 8 display short and long IPv4 addresses.


Note

The IPv6 address output display applies to all commands that display IPv6 addresses.


Simplified IPv6 Packet Header

The basic IPv4 packet header has 12 fields with a total size of 20 octets (160 bits) (see the figure below). The 12 fields may be followed by an Options field, which is followed by a data portion that is usually the transport-layer packet. The variable length of the Options field adds to the total size of the IPv4 packet header. The shaded fields of the IPv4 packet header shown in the figure below are not included in the IPv6 packet header.

Figure 6. IPv4 Packet Header Format

The basic IPv6 packet header has 8 fields with a total size of 40 octets (320 bits) (see the figure below). Fields were removed from the IPv6 header because, in IPv6, fragmentation is not handled by devices and checksums at the network layer are not used. Instead, fragmentation in IPv6 is handled by the source of a packet and checksums at the data link layer and transport layer are used. (In IPv4, the UDP transport layer uses an optional checksum. In IPv6, use of the UDP checksum is required to check the integrity of the inner packet.) Additionally, the basic IPv6 packet header and Options field are aligned to 64 bits, which can facilitate the processing of IPv6 packets.

Figure 7. IPv6 Packet Header Format

The table below lists the fields in the basic IPv6 packet header.

Table 2. Basic IPv6 Packet Header Fields

Field

Description

Version

Similar to the Version field in the IPv4 packet header, except that the field lists number 6 for IPv6 instead of number 4 for IPv4.

Traffic Class

Similar to the Type of Service field in the IPv4 packet header. The Traffic Class field tags packets with a traffic class that is used in differentiated services.

Flow Label

A new field in the IPv6 packet header. The Flow Label field tags packets with a specific flow that differentiates the packets at the network layer.

Payload Length

Similar to the Total Length field in the IPv4 packet header. The Payload Length field indicates the total length of the data portion of the packet.

Next Header

Similar to the Protocol field in the IPv4 packet header. The value of the Next Header field determines the type of information following the basic IPv6 header. The type of information following the basic IPv6 header can be a transport-layer packet, for example, a TCP or UDP packet, or an Extension Header, as shown in the figure immediately above.

Hop Limit

Similar to the Time to Live field in the IPv4 packet header. The value of the Hop Limit field specifies the maximum number of devices that an IPv6 packet can pass through before the packet is considered invalid. Each device decrements the value by one. Because no checksum is in the IPv6 header, the device can decrement the value without needing to recalculate the checksum, which saves processing resources.

Source Address

Similar to the Source Address field in the IPv4 packet header, except that the field contains a 128-bit source address for IPv6 instead of a 32-bit source address for IPv4.

Destination Address

Similar to the Destination Address field in the IPv4 packet header, except that the field contains a 128-bit destination address for IPv6 instead of a 32-bit destination address for IPv4.

Following the eight fields of the basic IPv6 packet header are optional extension headers and the data portion of the packet. If present, each extension header is aligned to 64 bits. There is no fixed number of extension headers in an IPv6 packet. The extension headers form a chain of headers. Each extension header is identified by the Next Header field of the previous header. Typically, the final extension header has a Next Header field of a transport-layer protocol, such as TCP or UDP. The figure below shows the IPv6 extension header format.

Figure 8. IPv6 Extension Header Format

The table below lists the extension header types and their Next Header field values.

Table 3. IPv6 Extension Header Types

Header Type

Next Header Value

Description

Hop-by-hop options header

0

This header is processed by all hops in the path of a packet. When present, the hop-by-hop options header always follows immediately after the basic IPv6 packet header.

Destination options header

60

The destination options header can follow any hop-by-hop options header, in which case the destination options header is processed at the final destination and also at each visited address specified by a routing header. Alternatively, the destination options header can follow any Encapsulating Security Payload (ESP) header, in which case the destination options header is processed only at the final destination.

Routing header

43

The routing header is used for source routing.

Fragment header

44

The fragment header is used when a source must fragment a packet that is larger than the maximum transmission unit (MTU) for the path between itself and a destination. The Fragment header is used in each fragmented packet.

Authentication header

and

ESP header

51

50

The Authentication header and the ESP header are used within IP Security Protocol (IPsec) to provide authentication, integrity, and confidentiality of a packet. These headers are identical for both IPv4 and IPv6.

Upper-layer headers

6 (TCP)

17 (UDP)

The upper-layer (transport) headers are the typical headers used inside a packet to transport the data. The two main transport protocols are TCP and UDP.

Mobility headers

135

Extension headers used by mobile nodes, correspondent nodes, and home agents in all messaging related to the creation and management of bindings.

Cisco Express Forwarding for IPv6

Cisco Express Forwarding is advanced, Layer 3 IP switching technology for the forwarding of IPv6 packets.

Each IPv6 router interface has an association to one IPv6 global FIB and one IPv6 link-local FIB (multiple interfaces can have an association to the same FIB). All IPv6 router interfaces that are attached to the same IPv6 link share the same IPv6 link-local FIB. IPv6 packets that have an IPv6 global destination address are processed by the IPv6 global FIB; however, packets that have an IPv6 global destination address and an IPv6 link-local source address are sent to the RP for process switching and scope-error handling. Packets that have a link-local source address are not forwarded off of the local link and are sent to the RP for process switching and scope-error handling.

Unicast Reverse Path Forwarding

Use the Unicast Reverse Path Forwarding for IPv6 feature to mitigate problems caused by malformed or spoofed IPv6 source addresses that pass through an IPv6 device. Malformed or forged source addresses can indicate denial-of-service (DoS) attacks based on source IPv6 address spoofing.

When uRPF is enabled on an interface, the device examines all packets received on that interface. The device verifies that the source address appears in the routing table and matches the interface on which the packet was received. This "look backward" ability is available only when Cisco Express Forwarding is enabled on the device; this is because the lookup relies on the presence of the Forwarding Information Bases (FIBs). Cisco Express Forwarding generates the FIB as part of its operation.


Note

uRPF is an input function and is applied only on the input interface of a device at the upstream end of a connection.



Note

With uRPF, all equal-cost "best" return paths are considered valid. uRPF works in cases where multiple return paths exist, provided that each path is equal to the others in terms of the routing cost (number of hops, weights, and so on) and as long as the route is in the FIB.


DNS for IPv6

IPv6 supports DNS record types that are supported in the DNS name-to-address and address-to-name lookup processes. The DNS record types support IPv6 addresses. IPv6 also supports the reverse mapping of IPv6 addresses to DNS names.

The table below lists the IPv6 DNS record types.

Table 4. IPv6 DNS Record Types

Record Type

Description

Format

AAAA

Maps a hostname to an IPv6 address. (Equivalent to an A record in IPv4.)

www.abc.test AAAA 3FFE:YYYY:C18:1::2

PTR

Maps an IPv6 address to a hostname. (Equivalent to a PTR record in IPv4.)

Note 

Cisco software supports resolution of PTR records for the IP6.INT domain.

2.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.0.0.0.8.1.c.0.y.y.y.y.e.f.f.3.ip6.int PTR www.abc.test

Cisco Discovery Protocol IPv6 Address Support

The Cisco Discovery Protocol IPv6 address support for neighbor information feature adds the ability to transfer IPv6 addressing information between two Cisco devices. Cisco Discovery Protocol support for IPv6 addresses provides IPv6 information to network management products and troubleshooting tools.

ICMP for IPv6

Internet Control Message Protocol (ICMP) in IPv6 functions the same as ICMP in IPv4. ICMP generates error messages, such as ICMP destination unreachable messages, and informational messages, such as ICMP echo request and reply messages. Additionally, ICMP packets in IPv6 are used in the IPv6 neighbor discovery process, path MTU discovery, and the Multicast Listener Discovery (MLD) protocol for IPv6. MLD is used by IPv6 devices to discover multicast listeners (nodes that want to receive multicast packets destined for specific multicast addresses) on directly attached links. MLD is based on version 2 of the Internet Group Management Protocol (IGMP) for IPv4.

A value of 58 in the Next Header field of the basic IPv6 packet header identifies an IPv6 ICMP packet. ICMP packets in IPv6 are like a transport-layer packet in the sense that the ICMP packet follows all the extension headers and is the last piece of information in the IPv6 packet. Within IPv6 ICMP packets, the ICMPv6 Type and ICMPv6 Code fields identify IPv6 ICMP packet specifics, such as the ICMP message type. The value in the Checksum field is derived (computed by the sender and checked by the receiver) from the fields in the IPv6 ICMP packet and the IPv6 pseudoheader. The ICMPv6 Data field contains error or diagnostic information relevant to IP packet processing. The figure below shows the IPv6 ICMP packet header format.

Figure 9. IPv6 ICMP Packet Header Format

IPv6 ICMP Rate Limiting

The IPv6 ICMP rate limiting feature implements a token bucket algorithm for limiting the rate at which IPv6 ICMP error messages are sent out on the network. The initial implementation of IPv6 ICMP rate limiting defined a fixed interval between error messages, but some applications such as traceroute often require replies to a group of requests sent in rapid succession. The fixed interval between error messages is not flexible enough to work with applications such as traceroute and can cause the application to fail.

Implementing a token bucket scheme allows a number of tokens--representing the ability to send one error message each--to be stored in a virtual bucket. The maximum number of tokens allowed in the bucket can be specified, and for every error message to be sent, one token is removed from the bucket. If a series of error messages is generated, error messages can be sent until the bucket is empty. When the bucket is empty of tokens, no IPv6 ICMP error messages are sent until a new token is placed in the bucket. The token bucket algorithm does not increase the average rate limiting time interval, and it is more flexible than the fixed time interval scheme.

IPv6 MTU Path Discovery

As in IPv4, path MTU discovery in IPv6 allows a host to dynamically discover and adjust to differences in the MTU size of every link along a given data path. In IPv6, however, fragmentation is handled by the source of a packet when the path MTU of one link along a given data path is not large enough to accommodate the size of the packets. Having IPv6 hosts handle packet fragmentation saves IPv6 device processing resources and helps IPv6 networks run more efficiently.


Note

In IPv6, the minimum link MTU is 1280 octets. We recommend using an MTU value of 1500 octets for IPv6 links.


With IPv6 path MTU discovery, a device originating IPv6 traffic has an MTU cache that contains MTU values received in ICMPv6 "toobig" messages. In order to prevent an attacker from filling the MTU cache, the device keeps track of the destinations to which it has originated (sent) traffic, and only accepts toobig ICMPv6 messages that have an inner destination matching one of these tracked destinations.

If a malicious device can learn to which destination the device is originating traffic, it could still send a toobig ICMPv6 message to the device for this destination, even if the attacker is not on the path to this destination, and succeeds in forcing his entry into the MTU cache. The device then starts fragmenting traffic to this destination, which significantly affects device performance.

Enabling flow-label marking for locally generated traffic can mitigate this attack. Originated packets are marked with a flow label (which is randomly generated and changed every minute), and toobig messages received are checked against the values sent. Unless an attacker can snoop traffic, the attacker will not know which flow label to use, and its toobig message will be dropped.

IPv6 Neighbor Discovery

The IPv6 neighbor discovery process uses ICMP messages and solicited-node multicast addresses to determine the link-layer address of a neighbor on the same network (local link), verify the reachability of a neighbor, and track neighboring devices.

The IPv6 static cache entry for neighbor discovery feature allows static entries to be made in the IPv6 neighbor cache. Static routing requires an administrator to manually enter IPv6 addresses, subnet masks, gateways, and corresponding Media Access Control (MAC) addresses for each interface of each device into a table. Static routing enables more control but requires more work to maintain the table. The table must be updated each time routes are added or changed.

Stateful Switchover

IPv6 neighbor discovery supports stateful switchover (SSO) using Cisco Express Forwarding. When switchover occurs, the Cisco Express Forwarding adjacency state, which is checkpointed, is used to reconstruct the neighbor discovery cache.

SSO and ISSU Support for Per-User IPv6 ACL for PPP Sessions

The Stateful Switchover (SSO) and In Service Software Upgrade (ISSU) support for per-user IPv6 ACL for PPP sessions feature reproduces IPv6 ACLs on the active RP to the standby RP, which provide a consistent SSO and ISSU experience for active sessions.

IPv6 Neighbor Solicitation Message

A value of 135 in the Type field of the ICMP packet header identifies a neighbor solicitation message. Neighbor solicitation messages are sent on the local link when a node wants to determine the link-layer address of another node on the same local link (see the figure below). When a node wants to determine the link-layer address of another node, the source address in a neighbor solicitation message is the IPv6 address of the node sending the neighbor solicitation message. The destination address in the neighbor solicitation message is the solicited-node multicast address that corresponds to the IPv6 address of the destination node. The neighbor solicitation message also includes the link-layer address of the source node.

Figure 10. IPv6 Neighbor Discovery: Neighbor Solicitation Message

After receiving the neighbor solicitation message, the destination node replies by sending a neighbor advertisement message, which has a value of 136 in the Type field of the ICMP packet header, on the local link. The source address in the neighbor advertisement message is the IPv6 address of the node (more specifically, the IPv6 address of the node interface) sending the neighbor advertisement message. The destination address in the neighbor advertisement message is the IPv6 address of the node that sent the neighbor solicitation message. The data portion of the neighbor advertisement message includes the link-layer address of the node sending the neighbor advertisement message.

After the source node receives the neighbor advertisement, the source node and destination node can communicate.

Neighbor solicitation messages are also used to verify the reachability of a neighbor after the link-layer address of a neighbor is identified. When a node wants to verify the reachability of a neighbor, the destination address in a neighbor solicitation message is the unicast address of the neighbor.

Neighbor advertisement messages are also sent when there is a change in the link-layer address of a node on a local link. When there is such a change, the destination address for the neighbor advertisement is the all-nodes multicast address.

Neighbor solicitation messages are also used to verify the reachability of a neighbor after the link-layer address of a neighbor is identified. Neighbor unreachability detection identifies the failure of a neighbor or the failure of the forward path to the neighbor, and is used for all paths between hosts and neighboring nodes (hosts or devices). Neighbor unreachability detection is performed for neighbors to which only unicast packets are being sent and is not performed for neighbors to which multicast packets are being sent.

A neighbor is considered reachable when a positive acknowledgment is returned from the neighbor (indicating that packets previously sent to the neighbor have been received and processed). A positive acknowledgment from an upper-layer protocol (such as TCP) indicates that a connection is making forward progress (reaching its destination) or the receipt of a neighbor advertisement message in response to a neighbor solicitation message. If packets are reaching the peer, they are also reaching the next-hop neighbor of the source. Therefore, forward progress is also a confirmation that the next-hop neighbor is reachable.

For destinations that are not on the local link, forward progress implies that the first-hop device is reachable. When acknowledgments from an upper-layer protocol are not available, a node probes the neighbor using unicast neighbor solicitation messages to verify that the forward path is still working.

The return of a solicited neighbor advertisement message from the neighbor is a positive acknowledgment that the forward path is still working (neighbor advertisement messages that have the solicited flag set to a value of 1 are sent only in response to a neighbor solicitation message). Unsolicited messages confirm only the one-way path from the source to the destination node; solicited neighbor advertisement messages indicate that a path is working in both directions.


Note

A neighbor advertisement message that has the solicited flag set to a value of 0 must not be considered as a positive acknowledgment that the forward path is still working.


Neighbor solicitation messages are also used in the stateless autoconfiguration process to verify the uniqueness of unicast IPv6 addresses before the addresses are assigned to an interface. Duplicate address detection is performed first on a new, link-local IPv6 address before the address is assigned to an interface (the new address remains in a tentative state while duplicate address detection is performed). Specifically, a node sends a neighbor solicitation message with an unspecified source address and a tentative link-local address in the body of the message. If another node is already using that address, the node returns a neighbor advertisement message that contains the tentative link-local address. If another node is simultaneously verifying the uniqueness of the same address, that node also returns a neighbor solicitation message. If no neighbor advertisement messages are received in response to the neighbor solicitation message and no neighbor solicitation messages are received from other nodes that are attempting to verify the same tentative address, the node that sent the original neighbor solicitation message considers the tentative link-local address to be unique and assigns the address to the interface.

Every IPv6 unicast address (global or link-local) must be verified for uniqueness on the link; however, until the uniqueness of the link-local address is verified, duplicate address detection is not performed on any other IPv6 addresses associated with the link-local address. The Cisco implementation of duplicate address detection in the Cisco software does not verify the uniqueness of anycast or global addresses that are generated from 64-bit interface identifiers.

IPv6 Router Advertisement Message

Router advertisement (RA) messages, which have a value of 134 in the Type field of the ICMP packet header, are periodically sent out each configured interface of an IPv6 router. For stateless autoconfiguration to work properly, the advertised prefix length in RA messages must always be 64 bits.

The RA messages are sent to the all-nodes multicast address (see the figure below).

Figure 11. IPv6 Neighbor Discovery--RA Message

RA messages typically include the following information:

  • One or more onlink IPv6 prefixes that nodes on the local link can use to automatically configure their IPv6 addresses

  • Lifetime information for each prefix included in the advertisement

  • Sets of flags that indicate the type of autoconfiguration (stateless or stateful) that can be completed

  • Default router information (whether the router sending the advertisement should be used as a default router and, if so, the amount of time (in seconds) the router should be used as a default router)

  • Additional information for hosts, such as the hop limit and MTU a host should use in packets that it originates

RAs are also sent in response to router solicitation messages.

The following RA message parameters can be configured:

  • The time interval between periodic RA messages

  • The "router lifetime" value, which indicates the usefulness of a router as the default router (for use by all nodes on a given link)

  • The network prefixes in use on a given link

  • The time interval between neighbor solicitation message retransmissions (on a given link)

  • The amount of time a node considers a neighbor reachable (for use by all nodes on a given link)

The configured parameters are specific to an interface. The sending of RA messages (with default values) is automatically enabled on FDDI interfaces when the ipv6 unicast-routing command is configured. For other interface types, the sending of RA messages must be manually configured by using the no ipv6 nd ra suppress command. The sending of RA messages can be disabled on individual interfaces by using the ipv6 nd ra suppress command.

Default Router Preferences for Traffic Engineering

Hosts discover and select default devices by listening to router advertisements (RAs). Typical default device selection mechanisms are suboptimal in certain cases, such as when traffic engineering is needed. For example, two devices on a link may provide equivalent but not equal-cost routing, and policy may dictate that one of the devices is preferred. Some examples are as follows:

  • Multiple devices that route to distinct sets of prefixes--Redirects (sent by nonoptimal devices for a destination) mean that hosts can choose any device and the system will work. However, traffic patterns may mean that choosing one of the devices would lead to considerably fewer redirects.

  • Accidentally deploying a new device--Deploying a new device before it has been fully configured could lead to hosts adopting the new device as a default device and traffic disappearing. Network managers may want to indicate that some devices are more preferred than others.

  • Multihomed situations--Multihomed situations may become more common, because of multiple physical links and because of the use of tunneling for IPv6 transport. Some of the devices may not provide full default routing because they route only to the 6-to-4 prefix or they route only to a corporate intranet. These situations cannot be resolved with redirects, which operate only over a single link.

IPv6 Neighbor Redirect Message

A value of 137 in the type field of the ICMP packet header identifies an IPv6 neighbor redirect message. Devices send neighbor redirect messages to inform hosts of better first-hop nodes on the path to a destination (see the figure below).

Figure 12. IPv6 Neighbor Discovery: Neighbor Redirect Message

Note

A device must be able to determine the link-local address for each of its neighboring devices in order to ensure that the target address (the final destination) in a redirect message identifies the neighbor device by its link-local address. For static routing, the address of the next-hop device should be specified using the link-local address of the device; for dynamic routing, all IPv6 routing protocols must exchange the link-local addresses of neighboring devices.


After forwarding a packet, a device should send a redirect message to the source of the packet under the following circumstances:

  • The destination address of the packet is not a multicast address.

  • The packet was not addressed to the device.

  • The packet is about to be sent out the interface on which it was received.

  • The device determines that a better first-hop node for the packet resides on the same link as the source of the packet.

  • The source address of the packet is a global IPv6 address of a neighbor on the same link, or a link-local address.

Use the ipv6 icmp error-interval command to limit the rate at which the device generates all IPv6 ICMP error messages, including neighbor redirect messages, which ultimately reduces link-layer congestion.


Note

A device must not update its routing tables after receiving a neighbor redirect message, and hosts must not originate neighbor redirect messages.


Per-Interface Neighbor Discovery Cache Limit

The number of entries in the Neighbor Discovery cache can be limited by interface. Once the limit is reached, no new entries are allowed. The per-interface Neighbor Discovery cache limit function can be used to prevent any particular customer attached to an interface from overloading the Neighbor Discovery cache, whether intentionally or unintentionally.

When this feature is enabled globally, a common per-interface cache size limit is configured on all interfaces on the device. When this feature is enabled per interface, a cache size limit is configured on the associated interface. The per-interface limit overrides any globally configured limit.

Link, Subnet, and Site Addressing Changes

This section describes the IPv6 stateless autoconfiguration and general prefix features, which can be used to manage link, subnet, and site addressing changes.

IPv6 Stateless Autoconfiguration

All interfaces on IPv6 nodes must have a link-local address, which is usually automatically configured from the identifier for an interface and the link-local prefix FE80::/10. A link-local address enables a node to communicate with other nodes on the link and can be used to further configure the node.

Nodes can connect to a network and automatically generate global IPv6 addresses without the need for manual configuration or help of a server, such as a Dynamic Host Configuration Protocol (DHCP) server. With IPv6, a device on the link advertises any global prefixes in Router Advertisement (RA) messages, as well as its willingness to function as a default device for the link. RA messages are sent periodically and in response to device solicitation messages, which are sent by hosts at system startup.

A node on the link can automatically configure global IPv6 addresses by appending its interface identifier (64 bits) to the prefixes (64 bits) included in the RA messages. The resulting 128-bit IPv6 addresses configured by the node are then subjected to duplicate address detection to ensure their uniqueness on the link. If the prefixes advertised in the RA messages are globally unique, then the IPv6 addresses configured by the node are also guaranteed to be globally unique. Device solicitation messages, which have a value of 133 in the Type field of the ICMP packet header, are sent by hosts at system startup so that the host can immediately autoconfigure without needing to wait for the next scheduled RA message.

Simplified Network Renumbering for IPv6 Hosts

The strict aggregation of the global routing table requires that networks be renumbered when the service provider for the network is changed. When the stateless autoconfiguration functionality in IPv6 is used to renumber a network, the prefix from a new service provider is added to RA messages that are sent on the link. (The RA messages contain both the prefix from the old service provider and the prefix from the new service provider.) Nodes on the link automatically configure additional addresses by using the prefix from the new service provider. The nodes can then use the addresses created from the new prefix and the existing addresses created from the old prefix on the link. Configuration of the lifetime parameters associated with the old and new prefixes means that nodes on the link can make the transition to using only addresses created from the new prefix. During a transition period, the old prefix is removed from RA messages and only addresses that contain the new prefix are used on the link (the renumbering is complete) (see the figure below).

Figure 13. IPv6 Network Renumbering for Hosts Using Stateless Autoconfiguration

IPv6 General Prefixes

The upper 64 bits of an IPv6 address are composed from a global routing prefix plus a subnet ID, as defined in RFC 3513. A general prefix (for example, /48) holds a short prefix, based on which a number of longer, more-specific prefixes (for example, /64) can be defined. When the general prefix is changed, all of the more-specific prefixes based on it will change, too. This function greatly simplifies network renumbering and allows for automated prefix definition.

For example, a general prefix might be 48 bits long (“/48”) and the more specific prefixes generated from it might be 64 bits long (“/64”). In the following example, the leftmost 48 bits of all the specific prefixes will be the same, and they are the same as the general prefix itself. The next 16 bits are all different.

 General prefix: 2001:DB8:2222::/48
Specific prefix: 2001:DB8:2222:0000::/64
Specific prefix: 2001:DB8:2222:0001::/64
Specific prefix: 2001:DB8:2222:4321::/64
Specific prefix: 2001:DB8:2222:7744::/64

General prefixes can be defined in several ways:

  • Manually

  • Based on a 6to4 interface

  • Dynamically, from a prefix received by a Dynamic Host Configuration Protocol (DHCP) for IPv6 prefix delegation client

More specific prefixes, based on a general prefix, can be used when configuring IPv6 on an interface.

DHCP for IPv6 Prefix Delegation

DHCP for IPv6 can be used in environments to deliver stateful and stateless information. For further information about this feature, see Implementing DHCP for IPv6.

IPv6 Prefix Aggregation

The aggregatable nature of the IPv6 address space enables an IPv6 addressing hierarchy. For example, an enterprise can subdivide a single IPv6 prefix from a service provider into multiple, longer prefixes for use within its internal network. Conversely, a service provider can aggregate all of the prefixes of its customers into a single, shorter prefix that the service provider can then advertise over the IPv6 internet (see the figure below).

Figure 14. IPv6 Prefix Aggregation

IPv6 Site Multihoming

Multiple IPv6 prefixes can be assigned to networks and hosts. Having multiple prefixes assigned to a network allows that network to connect easily to multiple ISPs without breaking the global routing table (see the figure below).

Figure 15. IPv6 Site Multihoming

IPv6 Data Links

In IPv6 networks, a data link is a network sharing a particular link-local prefix. Data links are networks arbitrarily segmented by a network administrator in order to provide a multilevel, hierarchical routing structure while shielding the subnetwork from the addressing complexity of attached networks. The function of a subnetwork in IPv6 is similar to a subnetwork in IPv4. A subnetwork prefix is associated with one data link; multiple subnetwork prefixes may be assigned to the same data link.

The following data links are supported for IPv6: FDDI, Frame Relay PVC, Cisco High-Level Data Link Control (HDLC), PPP over Packet over SONET, ISDN, and serial interfaces.

How to Implement IPv6 Addressing and Basic Connectivity

Configuring IPv6 Addressing and Enabling IPv6 Routing

Perform this task to assign IPv6 addresses to individual device interfaces and enable IPv6 traffic forwarding globally on the device. By default, IPv6 addresses are not configured and IPv6 routing is disabled.


Note

Multiple IPv6 link-local addresses on an interface are not supported.

>

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. interface type number
  4. Do one of the following:
    • ipv6 address ipv6-prefix /prefix-length eui-64
    • ipv6 address ipv6-address / prefix-length link-local
    • ipv6 enable
  5. exit
  6. ipv6 unicast-routing

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:


Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:


Device# configure terminal

Enters global configuration mode.

Step 3

interface type number

Example:


Device(config)# interface gigabitethernet 0/0/0

Specifies an interface type and number, and places the device in interface configuration mode.

Step 4

Do one of the following:

  • ipv6 address ipv6-prefix /prefix-length eui-64
  • ipv6 address ipv6-address / prefix-length link-local
  • ipv6 enable

Example:


Device(config-if)# ipv6 address 2001:DB8:0:1::/64 eui-64

Example:


          

Example:


Device(config-if)# ipv6 address FE80::260:3EFF:FE11:6770 link-local

Example:


Example:


          

Example:


Device(config-if)# ipv6 enable

Specifies an IPv6 network assigned to the interface and enables IPv6 processing on the interface.

or

Specifies an IPv6 address assigned to the interface and enables IPv6 processing on the interface.

or

Automatically configures an IPv6 link-local address on the interface while also enabling the interface for IPv6 processing. The link-local address can be used only to communicate with nodes on the same link.

  • Specifying the ipv6 address eui-64 command configures global IPv6 addresses with an interface identifier (ID) in the low-order 64 bits of the IPv6 address. Only the 64-bit network prefix for the address needs to be specified; the last 64 bits are automatically computed from the interface ID.

  • Specifying the ipv6 address link-local command configures a link-local address on the interface that is used instead of the link-local address that is automatically configured when IPv6 is enabled on the interface.

Step 5

exit

Example:


Device(config-if)# exit

Exits interface configuration mode, and returns the device to global configuration mode.

Step 6

ipv6 unicast-routing

Example:


Device(config)# ipv6 unicast-routing

Enables the forwarding of IPv6 unicast datagrams.

Configuring a Neighbor Discovery Cache Limit

Configuring a Neighbor Discovery Cache Limit on a Specified Interface

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. interface type number
  4. ipv6 nd cache interface-limit size [log rate ]

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

interface type number

Example:

Device(config)# interface GigabitEthernet 1/0/0

Specifies an interface type and number, and places the device in interface configuration mode.

Step 4

ipv6 nd cache interface-limit size [log rate ]

Example:

Device(config-if)# ipv6 nd cache interface-limit 1

Configures a Neighbor Discovery cache limit on a specified interface on the device.

  • Issuing this command overrides any configuration that may have been created by issuing the ipv6 nd cache interface-limit in global configuration mode.

Configuring a Neighbor Discovery Cache Limit on All Device Interfaces

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. ipv6 nd cache interface-limit size [log rate ]

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:

Device> enable 

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

ipv6 nd cache interface-limit size [log rate ]

Example:

Device(config)# ipv6 nd cache interface-limit 4 

Configures a neighbor discovery cache limit on all interfaces on the device.

Defining and Using IPv6 General Prefixes

General prefixes can be defined in several ways:

  • Manually

  • Based on a 6to4 interface

  • Dynamically, from a prefix received by a DHCP for IPv6 prefix delegation client

More specific prefixes, based on a general prefix, can be used when configuring IPv6 on an interface.

Defining a General Prefix Manually

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. ipv6 general-prefix prefix-name {ipv6-prefix/prefix-length | 6to4 interface-type interface-number}

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

ipv6 general-prefix prefix-name {ipv6-prefix/prefix-length | 6to4 interface-type interface-number}

Example:

Device(config)# ipv6 general-prefix my-prefix 2001:DB8:2222::/48

Defines a general prefix for an IPv6 address.

Defining a General Prefix Based on a 6to4 Interface

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. ipv6 general-prefix prefix-name {ipv6-prefix / prefix-length | 6to4 interface-type interface-number

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

ipv6 general-prefix prefix-name {ipv6-prefix / prefix-length | 6to4 interface-type interface-number

Example:

Router(config)# ipv6 general-prefix my-prefix 6to4 gigabitethernet 0/0/0

Defines a general prefix for an IPv6 address.

When defining a general prefix based on a 6to4 interface, specify the 6to4 keyword and the interface-type interface-number arguments.

When defining a general prefix based on an interface used for 6to4 tunneling, the general prefix will be of the form 2001:a.b.c.d::/48, where "a.b.c.d" is the IPv4 address of the interface referenced.

Defining a General Prefix with the DHCP for IPv6 Prefix Delegation Client Function

You can define a general prefix dynamically using the DHCP for IPv6 prefix delegation client function. For information on how to perform this task, see the Implementing DHCP for IPv6 module.

Using a General Prefix in IPv6

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. interface type number
  4. ipv6 address {ipv6-address / prefix-length | prefix-name sub-bits /prefix-length

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

interface type number

Example:

Router(config)# interface gigabitethernet 0/0/0

Specifies an interface type and number, and places the router in interface configuration mode.

Step 4

ipv6 address {ipv6-address / prefix-length | prefix-name sub-bits /prefix-length

Example:

Router(config-if) ipv6 address my-prefix 2001:DB8:0:7272::/64

Configures an IPv6 prefix name for an IPv6 address and enables IPv6 processing on the interface.

Customizing IPv6 ICMP Rate Limiting

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. ipv6 icmp error-interval milliseconds [bucketsize ]

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:


Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:


Device# configure terminal

Enters global configuration mode.

Step 3

ipv6 icmp error-interval milliseconds [bucketsize ]

Example:


Device(config)# ipv6 icmp error-interval 50 20

Customizes the interval and bucket size for IPv6 ICMP error messages.

Enabling Flow-Label Marking in Packets that Originate from the Device

This feature allows the device to track destinations to which the device has sent packets that are 1280 bytes or larger.

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. ipv6 flowset
  4. exit
  5. clear ipv6 mtu

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:


Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:


Device# configure terminal

Enters global configuration mode.

Step 3

ipv6 flowset

Example:


Device(config)# ipv6 flowset 

Configures flow-label marking in 1280-byte or larger packets sent by the device.

Step 4

exit

Example:

Device(config)# exit

Exits global configuration mode, and places the device in privileged EXEC mode.

Step 5

clear ipv6 mtu

Example:

Device# clear ipv6 mtu

Clears the MTU cache of messages.

Clearing Messages from the IPv6 MTU Cache

SUMMARY STEPS

  1. enable
  2. clear ipv6 mtu

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted

Step 2

clear ipv6 mtu

Example:

Device# clear ipv6 mtu

Clears the MTU cache of messages.

Configuring the DRP Extension for Traffic Engineering

Perform this task to configure the DRP extension to RAs in order to signal the preference value of a default router.

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. interface type number
  4. ipv6 nd router-preference {high | medium | low

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:


Router> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:


Router# configure terminal

Enters global configuration mode.

Step 3

interface type number

Example:


Router(config)# interface gigabitethernet 0/0/0

Specifies the interface type and number, and enters interface configuration mode.

Step 4

ipv6 nd router-preference {high | medium | low

Example:


Router(config-if)# ipv6 nd router-preference high 

Configures a DRP for a router on a specific interface

Configuring Cisco Express Forwarding and Distributed Cisco Express Forwarding Switching for IPv6

Configuring Cisco Express Forwarding

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. Do the following:
    • ipv6 cef
  4. ipv6 cef accounting [non-recursive | per-prefix | prefix-length ]

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

Do the following:

  • ipv6 cef
Example:

Device(config)# ipv6 cef

Enables Cisco Express Forwarding globally on the device.

Step 4

ipv6 cef accounting [non-recursive | per-prefix | prefix-length ]

Example:

Device(config)# ipv6 cef accounting 

Enables Cisco Express Forwarding network accounting globally on the device.

  • Network accounting for Cisco Express Forwarding enables you to better understand Cisco Express Forwarding traffic patterns within your network by collecting statistics specific to Cisco Express Forwarding traffic. For example, network accounting for Cisco Express Forwarding enables you to collect information such as the number of packets and bytes switched to a destination or the number of packets switched through a destination.

  • The optional per-prefix keyword enables the collection of the number of packets and bytes express forwarded to an IPv6 destination (or IPv6 prefix).

  • The optional prefix-length keyword enables the collection of the number of packets and bytes express forwarded to an IPv6 prefix length.

Note 

When Cisco Express Forwarding is enabled globally on the device, accounting information is collected at the RP.

Configuring Unicast RPF

Before you begin

To use uRPF, enable Cisco Express Forwarding switching or distributed Cisco Express Forwarding switching in the device. There is no need to configure the input interface for Cisco Express Forwarding switching. As long as Cisco Express Forwarding is running on the device, individual interfaces can be configured with other switching modes.


Note

Cisco Express Forwarding must be configured globally in the device. uRPF will not work without Cisco Express Forwarding.



Note

uRPF should not be used on interfaces that are internal to the network. Internal interfaces are likely to have routing asymmetry, meaning that there are multiple routes to the source of a packet. uRPF should be applied only where there is natural or configured symmetry.

For example, devices at the edge of the network of an ISP are more likely to have symmetrical reverse paths than devices that are in the core of the ISP network. Devices that are in the core of the ISP network have no guarantee that the best forwarding path out of the device will be the path selected for packets returning to the device. Therefore, we do not recommend that you apply uRPF where there is a chance of asymmetric routing. It is simplest to place uRPF only at the edge of a network or, for an ISP, at the customer edge of the network.


SUMMARY STEPS

  1. enable
  2. configure terminal
  3. interface type number
  4. ipv6 verify unicast source reachable-via {rx | any } [allow-default ] [allow-self-ping ] [access-list-name

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

interface type number

Example:

Device(config)# interface gigabitethernet 0/0/0

Specifies an interface type and number, and places the device in interface configuration mode.

Step 4

ipv6 verify unicast source reachable-via {rx | any } [allow-default ] [allow-self-ping ] [access-list-name

Example:

Device(config-if)# ipv6 verify unicast source reachable-via any

Verifies that a source address exists in the FIB table and enables uRPF.

Mapping Hostnames to IPv6 Addresses

Hostname-to-Address Mappings

A name server is used to track information associated with domain names. A name server can maintain a database of hostname-to-address mappings. Each name can map to one or more IPv4 addresses, IPv6 addresses, or both address types. In order to use this service to map domain names to IPv6 addresses, you must specify a name server and enable the DNS, which is the global naming scheme of the Internet that uniquely identifies network devices.

Cisco software maintains a cache of hostname-to-address mappings for use by the connect , telnet , and ping commands, related Telnet support operations, and many other commands that generate command output. This cache speeds the conversion of names to addresses.

Similar to IPv4, IPv6 uses a naming scheme that allows a network device to be identified by its location within a hierarchical name space that provides for domains. Domain names are joined with periods (.) as the delimiting characters. For example, Cisco is a commercial organization that is identified by a com domain name, so its domain name is cisco.com . A specific device in this domain, the FTP server, for example, is identified as ftp.cisco.com .

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. Do one of the following:
    • ip domain name [vrf vrf-name ] name
    • ip domain list [vrf vrf-name ] name
  4. ip name-server [vrf vrf-name ] server-address1 [server-address2...server-address6 ]
  5. ip domain-lookup

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

Do one of the following:

  • ip domain name [vrf vrf-name ] name
  • ip domain list [vrf vrf-name ] name
Example:

Device(config)# ip domain-name cisco.com
Example:

          
Example:

Device(config)# ip domain list cisco1.com

(Optional) Defines a default domain name that Cisco software will use to complete unqualified hostnames.

or

(Optional) Defines a list of default domain names to complete unqualified hostnames.

  • You can specify a default domain name that Cisco software will use to complete domain name requests. You can specify either a single domain name or a list of domain names. Any hostname that does not contain a complete domain name will have the default domain name you specify appended to it before the name is looked up.

Note 

The ip domain name and ip domain list commands are used to specify default domain names that can be used by both IPv4 and IPv6.

Step 4

ip name-server [vrf vrf-name ] server-address1 [server-address2...server-address6 ]

Example:

Device(config)# ip name-server 2001:DB8::250:8bff:fee8:f800 2001:DB8:0:f004::1

Specifies one or more hosts that supply name information.

  • Specifies one or more hosts (up to six) that can function as a name server to supply name information for DNS.

Note 

The server-address argument can be either an IPv4 or IPv6 address.

Step 5

ip domain-lookup

Example:

Device(config)# ip domain-lookup

Enables DNS-based address translation.

  • DNS is enabled by default.

Mapping IPv6 Addresses to IPv6 Frame Relay Interfaces

Perform this task to map IPv6 addresses to Frame Relay PVCs. Specifically, the steps in this section explain how to explicitly map IPv6 addresses to the Frame Relay PVCs used to reach the addresses.


Note

This task shows how to configure Frame Relay PVCs. Several of the steps are labeled optional because many networks will require only one type of PVC to be configured.


IPv6 for Cisco IOS XE Software Support for Wide-Area Networking Technologies

IPv6 for Cisco IOS XE software supports wide-area networking technologies such as Cisco HDLC, PPP over Packet over SONET (PoS), ISDN, and serial (synchronous and asynchronous) interface types, and Frame Relay PVCs. These technologies function the same in IPv6 as they do in IPv4--IPv6 does not enhance the technologies in any way.

IPv6 Addresses and PVCs

Broadcast and multicast are used in LANs to map protocol (network-layer) addresses to the hardware addresses of remote nodes (hosts and routers). Because using broadcast and multicast to map network-layer addresses to hardware addresses in circuit-based WANs such as Frame Relay networks is difficult to implement, these networks utilize implicit, explicit, and dynamic mappings for the network-layer addresses of remote nodes and the PVCs used to reach the addresses.

Assigning an IPv6 address to an interface by using the ipv6 address command defines the IPv6 addresses for the interface and the network that is directly connected to the interface. If only one PVC is terminated on the interface (the interface is a point-to-point interface), there is an implicit mapping between all of the IPv6 addresses on the network and the PVC used to reach the addresses (no additional address mappings are needed). If several PVCs are terminated on the interface (the interface is a point-to-multipoint interface), the frame-relay map ipv6 command is used to configure explicit mappings between the IPv6 addresses of the remote nodes and the PVCs used to reach the addresses.


Note

Given that IPv6 supports multiple address types, and depending on which applications or protocols are configured on a point-to-multipoint interface, you may need to configure multiple explicit mappings between the IPv6 addresses of the interface and the PVC used to reach the addresses. For example, explicitly mapping both the link-local and global IPv6 address of a point-to-multipoint interface to the PVC that the interface terminates ensures that the Interior Gateway Protocol (IGP) configured on the interface forwards traffic to and from the PVC correctly.


SUMMARY STEPS

  1. enable
  2. configure terminal
  3. interface type number
  4. protocol ipv6 ipv6-address [[no ] broadcast ]
  5. frame-relay map ipv6 ipv6-address dlci [broadcast ] [cisco ] [ietf ] [payload-compression packet-by-packet | frf9 stac [hardware-options ] | data-stream stac [hardware-options ]}]
  6. ipv6 address ipv6-address / prefix-length link-local

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

interface type number

Example:

Router(config)# interface serial 3

Specifies an interface type and number, and places the router in interface configuration mode.

Step 4

protocol ipv6 ipv6-address [[no ] broadcast ]

Example:

Router(config-if-atm-vc)# protocol ipv6 2001:DB8:2222:1003::45

(Optional) Maps the IPv6 address of a remote node to the PVC used to reach the address.

Step 5

frame-relay map ipv6 ipv6-address dlci [broadcast ] [cisco ] [ietf ] [payload-compression packet-by-packet | frf9 stac [hardware-options ] | data-stream stac [hardware-options ]}]

Example:

Router(config-if)# frame-relay map ipv6 FE80::E0:F727:E400:A 17 broadcast

(Optional) Maps the IPv6 address of a remote node to the data-link connection identifier (DLCI) of the PVC used to reach the address.

Step 6

ipv6 address ipv6-address / prefix-length link-local

Example:

Router(config-if)# ipv6 address 2001:DB8:2222:1044::46/64 link-local

Specifies an IPv6 network assigned to the interface and enables IPv6 processing on the interface.

  • In the context of this task, a link-local address of the node at the other end of the link is required for the IGP used in the network.

  • Specifying the ipv6 address link-local command configures a link-local address on the interface that is used instead of the link-local address that is automatically configured when IPv6 is enabled on the interface.

Displaying IPv6 Redirect Messages

SUMMARY STEPS

  1. enable
  2. show ipv6 interface [brief ] [type number ] [prefix ]
  3. show ipv6 route [ipv6-address | ipv6-prefix /prefix-length | protocol | interface-type interface-number ]
  4. show ipv6 traffic
  5. show hosts [vrf vrf-name | all | hostname | summary ]
  6. enable
  7. show running-config

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:


Device# enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

show ipv6 interface [brief ] [type number ] [prefix ]

Example:


Device# show ipv6 interface gigabitethernet 0/0/0

Displays the usability status of interfaces configured for IPv6.

Step 3

show ipv6 route [ipv6-address | ipv6-prefix /prefix-length | protocol | interface-type interface-number ]

Example:


Device# show ipv6 route

(Optional) Displays the current contents of the IPv6 routing table.

Step 4

show ipv6 traffic

Example:


Device# show ipv6 traffic

(Optional) Displays statistics about IPv6 traffic.

Step 5

show hosts [vrf vrf-name | all | hostname | summary ]

Example:


Device# show hosts

Displays the default domain name, the style of name lookup service, a list of name server hosts, and the cached list of hostnames and addresses.

Step 6

enable

Example:


Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 7

show running-config

Example:


Device# show running-config

Displays the current configuration running on the device.

Examples

Sample Output from the show ipv6 route Command

When the ipv6-address or ipv6-prefix/ prefix-length argument is specified, only route information for that address or network is displayed. The following is sample output from the show ipv6 route command when entered with the IPv6 prefix 2001:DB8::/35:


Router# show ipv6 route 2001:DB8::/35
IPv6 Routing Table - 261 entries
Codes: C - Connected, L - Local, S - Static, R - RIP, B - BGP
I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea
B 2001:DB8::/35 [20/3]
  via FE80::60:5C59:9E00:16, Tunnel1
Sample Output from the show ipv6 traffic Command

In the following example, the show ipv6 traffic command is used to display ICMP rate-limited counters:


Router# show ipv6 traffic
ICMP statistics:
  Rcvd: 188 input, 0 checksum errors, 0 too short
        0 unknown info type, 0 unknown error type
        unreach: 0 routing, 0 admin, 0 neighbor, 0 address, 0 port
        parameter: 0 error, 0 header, 0 option
        0 hopcount expired, 0 reassembly timeout,0 too big
        0 echo request, 0 echo reply
        0 group query, 0 group report, 0 group reduce
        1 router solicit, 175 router advert, 0 redirects
        0 neighbor solicit, 12 neighbor advert
  Sent: 7376 output, 56 rate-limited
        unreach: 0 routing, 15 admin, 0 neighbor, 0 address, 0 port
        parameter: 0 error, 0 header, 0 option
        0 hopcount expired, 0 reassembly timeout,0 too big
        15 echo request, 0 echo reply
        0 group query, 0 group report, 0 group reduce
        0 router solicit, 7326 router advert, 0 redirects
        2 neighbor solicit, 22 neighbor advert
Sample Output from the show frame-relay map Command

In the following example, the show frame-relay map command is used to verify that the IPv6 address of a remote node is mapped to the DLCI of the PVC used to reach the address. The following example shows that the link-local and global IPv6 addresses (FE80::E0:F727:E400:A and 2001:DB8:2222:1044::73; FE80::60:3E47:AC8:8 and 2001.DB8:2222:1044::72) of two remote nodes are explicitly mapped to DLCI 17 and DLCI 19, respectively. Both DLCI 17 and DLCI 19 are terminated on interface serial 3 of this node; therefore, interface serial 3 of this node is a point-to-multipoint interface.


Router# show frame-relay map 
Serial3 (up): ipv6 FE80::E0:F727:E400:A dlci 17(0x11,0x410), static, 
              broadcast, CISCO, status defined, active 
Serial3 (up): ipv6 2001:DB8:2222:1044::72 dlci 19(0x13,0x430), static, 
              CISCO, status defined, active 
Serial3 (up): ipv6 2001:DB8:2222:1044::73 dlci 17(0x11,0x410), static, 
              CISCO, status defined, active 
Serial3 (up): ipv6 FE80::60:3E47:AC8:8 dlci 19(0x13,0x430), static, 
              broadcast, CISCO, status defined, active 
Sample Output from the show hosts Command

The state of the name lookup system on the DHCP for IPv6 client can be displayed with the show hosts command:


Router# show hosts
Default domain is not set
Domain list:verybigcompany.com
Name/address lookup uses domain service
Name servers are 2001:DB8:A:B::1, 2001:DB8:3000:3000::42
Codes:UN - unknown, EX - expired, OK - OK, ?? - revalidate
       temp - temporary, perm - permanent
       NA - Not Applicable None - Not defined
Host                      Port  Flags      Age Type   Address(es)
sdfasfd                   None  (temp, UN)  0  IPv6
Sample Output from the show running-config Command

In the following example, the show running-config command is used to verify that IPv6 processing of packets is enabled globally on the router and on applicable interfaces, and that an IPv6 address is configured on applicable interfaces:


Router# show running-config
Building configuration...
Current configuration : 22324 bytes
!
! Last configuration change at 14:59:38 PST Tue Jan 16 2001
! NVRAM config last updated at 04:25:39 PST Tue Jan 16 2001 by bird
!
hostname Router
!
ipv6 unicast-routing
!
interface gigabitethernet0/0/0
 no ip route-cache
 no ip mroute-cache
 no keepalive
 media-type 10BaseT
        ipv6 address 2001:DB8:0:1::/64 eui-64

In the following example, the show running-config command is used to verify that Cisco Express Forwarding and network accounting for Cisco Express Forwarding have been enabled globally on a nondistributed architecture platform, and that Cisco Express Forwarding has been enabled on an IPv6 interface. The following output shows that both that Cisco Express Forwarding and network accounting for Cisco Express Forwarding have been enabled globally on the router, and that Cisco Express Forwarding has also been enabled on Gigabit Ethernet interface 0/0/0:


Router# show running-config
Building configuration... 
Current configuration : 22324 bytes 
! 
! Last configuration change at 14:59:38 PST Tue Jan 16 2001 
! NVRAM config last updated at 04:25:39 PST Tue Jan 16 2001 by bird 
! 
hostname Router
!
ip cef
ipv6 unicast-routing
ipv6 cef
ipv6 cef accounting prefix-length
!
!
interface gigabitethernet0/0/0
 ip address 10.4.9.11 255.0.0.0
 media-type 10BaseT
 ipv6 address 2001:DB8:C18:1::/64 eui-64
!

In the following example, the show running-config command is used to verify static hostname-to-address mappings, default domain names, and name servers in the hostname cache, and to verify that the DNS service is enabled:


Router# show running-config
Building configuration...
!
ipv6 host cisco-sj 2001:DB8:20:1::12
!
ip domain-name cisco.com
ip domain-lookup
ip name-server 2001:DB8:C01F:768::1

Configuration Examples for Implementing IPv6 Addressing and Basic Connectivity

Example: IPv6 Addressing and IPv6 Routing Configuration

In the following example, IPv6 is enabled on the device with both a link-local address and a global address based on the IPv6 prefix 2001:DB8:c18:1::/64. The EUI-64 interface ID is used in the low-order 64 bits of both addresses. Output from the show ipv6 interface command is included to show how the interface ID (260:3EFF:FE47:1530) is appended to the link-local prefix FE80::/64 of Gigabit Ethernet interface 0/0/0.


ipv6 unicast-routing
interface gigabitethernet 0/0/0
  ipv6 address 2001:DB8:c18:1::/64 eui-64
Device# show ipv6 interface gigabitethernet 0/0/0
Gigabitethernet0/0/0 is up, line protocol is up
 IPv6 is enabled, link-local address is FE80::260:3EFF:FE47:1530
  Global unicast address(es):
    2001:DB8:C18:1:260:3EFF:FE47:1530, subnet is 2001:DB8:C18:1::/64
  Joined group address(es):
    FF02::1
    FF02::2
    FF02::1:FF47:1530
    FF02::9
  MTU is 1500 bytes
  ICMP error messages limited to one every 500 milliseconds
  ND reachable time is 30000 milliseconds
  ND advertised reachable time is 0 milliseconds
  ND advertised retransmit interval is 0 milliseconds
  ND router advertisements are sent every 200 seconds
  ND router advertisements live for 1800 seconds
  Hosts use stateless autoconfig for addresses.

Example: Dual-Protocol Stacks Configuration

The following example enables the forwarding of IPv6 unicast datagrams globally on the device and configures Gigabit Ethernet interface 0/0/0 with both an IPv4 address and an IPv6 address:


ipv6 unicast-routing
interface gigabitethernet0/0/0
  ip address 192.168.99.1 255.255.255.0
 ipv6 address 2001:DB8:c18:1::3/64

Example: IPv6 ICMP Rate Limiting Configuration

The following example shows an interval of 50 milliseconds and a bucket size of 20 tokens being configured for IPv6 ICMP error messages:


ipv6 icmp error-interval 50 20

Example: Cisco Express Forwarding Configuration

In the following example, both Cisco Express Forwarding for IPv6 and network accounting for Cisco Express Forwarding for IPv6 have been enabled globally on a nondistributed architecture device, and Cisco Express Forwarding for IPv6 has been enabled on Gigabit Ethernet interface 0/0/0. The example also shows that the forwarding of IPv6 unicast datagrams has been configured globally on the device with the ipv6 unicast-routing command, an IPv6 address has been configured on Gigabit Ethernet interface 0/0/0 with the ipv6 address command, and Cisco Express Forwarding for IPv4 has been configured globally on the device with the ip cef command.


ip cef
ipv6 unicast-routing
ipv6 cef
ipv6 cef accounting prefix-length
interface gigabitethernet0/0/0
 ip address 10.4.9.11 255.0.0.0
 media-type 10BaseT
 ipv6 address 2001:DB8:C18:1::/64 eui-64

Example: Hostname-to-Address Mappings Configuration

The following example defines two static hostname-to-address mappings in the hostname cache, establishes a domain list with several alternate domain names to complete unqualified hostnames, specifies host 2001:DB8::250:8bff:fee8:f800 and host 2001:DB8:0:f004::1 as the name servers, and reenables the DNS service:




ip domain list domain1-list.com
ip domain list serviceprovider2-name.com
ip domain list college2-name.edu
ip name-server 2001:DB8::250:8bff:fee8:f800 2001:DB8:0:f004::1
ip domain-lookup

Example IPv6 Address to Frame Relay PVC Mapping Configuration

Example IPv6 Frame Relay PVC Mapping Configuration (Point-to-Point Interface)

In the following example, three nodes named Router A, Router B, and Router C make up a fully meshed network. Each node is configured with two PVCs, which provide an individual connection to each of the other two nodes. Each PVC is configured on a different point-to-point subinterface, which creates three unique IPv6 networks (2001:DB8:2222:1017:/64, 2001:DB8:2222:1018::/64, and 2001:DB8:2222:1019::/64). Therefore, the mappings between the IPv6 addresses of each node and the DLCI (DLCI 17, 18, and 19) of the PVC used to reach the addresses are implicit (no additional mappings are required).


Note

Given that each PVC in the following example is configured on a different point-to-point subinterface, the configuration in the following example can also be used in a network that is not fully meshed. Additionally, configuring each PVC on a different point-to-point subinterface can help simplify your routing protocol configuration. However, the configuration in the following example requires more than one IPv6 network, whereas configuring each PVC on point-to-multipoint interfaces requires only one IPv6 network.


Router A Configuration

interface Serial 3 
 encapsulation frame-relay 
! 
interface Serial3.17 point-to-point 
 description to Router B 
 ipv6 address 2001:DB8:2222:1017::46/64 
 frame-relay interface-dlci 17 
! 
interface Serial 3.19 point-to-point 
 description to Router C 
 ipv6 address 2001:DB8:2222:1019::46/64 
 frame-relay interface-dlci 19 
Router B Configuration

interface Serial 5 
 encapsulation frame-relay 
! 
interface Serial5.17 point-to-point 
 description to Router A 
 ipv6 address 2001:DB8:2222:1017::73/64 
 frame-relay interface-dlci 17 
! 
interface Serial5.18 point-to-point 
 description to Router C 
 ipv6 address 2001:DB8:2222:1018::73/64 
 frame-relay interface-dlci 18
Router C Configuration

interface Serial 0 
 encapsulation frame-relay 
! 
interface Serial0.18 point-to-point 
 description to Router B 
 ipv6 address 2001:DB8:2222:1018::72/64 
 frame-relay interface-dlci 18 
! 
interface Serial0.19 point-to-point 
 description to Router A 
 ipv6 address 2001:DB8:2222:1019::72/64 
 frame-relay interface-dlci 19 

Example IPv6 Frame Relay PVC Mapping Configuration (Point-to-Multipoint Interface)

In the following example, the same three nodes (Router A, Router B, and Router C) from the previous example make up a fully meshed network and each node is configured with two PVCs (which provide an individual connection to each of the other two nodes). However, the two PVCs on each node in the following example are configured on a single interface (serial 3, serial 5, and serial 10, respectively), which makes each interface a point-to-multipoint interface. Therefore, explicit mappings are required between the link-local and global IPv6 addresses of each interface on all three nodes and the DLCI (DLCI 17, 18, and 19) of the PVC used to reach the addresses.

Router A Configuration

interface Serial 3 
 encapsulation frame-relay 
 ipv6 address 2001:DB8:2222:1044::46/64 
 frame-relay map ipv6 FE80::E0:F727:E400:A 17 broadcast 
 frame-relay map ipv6 FE80::60:3E47:AC8:8 19 broadcast 
 frame-relay map ipv6 2001:DB8:2222:1044::72 19 
 frame-relay map ipv6 2001:DB8:2222:1044::73 17 
Router B Configuration

interface Serial 5 
 encapsulation frame-relay 
 ipv6 address 2001:DB8:2222:1044::73/64 
 frame-relay map ipv6 FE80::60:3E59:DA78:C 17 broadcast 
 frame-relay map ipv6 FE80::60:3E47:AC8:8 18 broadcast 
 frame-relay map ipv6 2001:DB8:2222:1044::46 17 
 frame-relay map ipv6 2001:DB8:2222:1044::72 18 
Router C Configuration

interface Serial 10 
 encapsulation frame-relay 
 ipv6 address 2001:DB8:2222:1044::72/64 
 frame-relay map ipv6 FE80::60:3E59:DA78:C 19 broadcast 
 frame-relay map ipv6 FE80::E0:F727:E400:A 18 broadcast 
 frame-relay map ipv6 2001:DB8:2222:1044::46 19 
 frame-relay map ipv6 2001:DB8:2222:1044::73 18 

Additional References

Related Documents

Related Topic

Document Title

IPv6 supported feature list

Start Here: Cisco IOS XE Software Release Specifics for IPv6 Features

IPv6 commands: complete command syntax, command mode, defaults, usage guidelines, and examples

Cisco IOS IPv6 Command Reference

IPv6 DHCP description and configuration

Implementing DHCP for IPv6

IPv4 addressing configuration tasks

Configuring IPv4 Addresses

IPv4 services configuration tasks

Configuring IP Services

IPv4 addressing commands

Cisco IOS IP Addressing Services Command Reference

IPv4 IP services commands

Cisco IOS IP Application Services Command Reference

Stateful Switchover

Configuring Stateful Switchover

In Service Software Upgrade

Cisco IOS XE In Service Software Upgrade Process

Switching commands

Cisco IOS IP Switching Command Reference

Cisco IOS master command list, all releases

Cisco IOS Master Command List, All Releases

Standards

Standards

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

--

MIBs

MIBs

MIBs Link

None

To locate and download MIBs for selected platforms, Cisco software releases, and feature sets, use Cisco MIB Locator found at the following URL:

http://www.cisco.com/go/mibs

RFCs

RFCs

Title

RFC 1981

Path MTU Discovery for IP version 6

RFC 2373

IP Version 6 Addressing Architecture

RFC 2374

An Aggregatable Global Unicast Address Format

RFC 2460

Internet Protocol, Version 6 (IPv6) Specification

RFC 2461

Neighbor Discovery for IP Version 6 (IPv6)

RFC 2462

IPv6 Stateless Address Autoconfiguration

RFC 2463

Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification

RFC 2467

Transmission of IPv6 Packets over FDDI Networks

RFC 2472

IP Version 6 over PPP

RFC 2590

Transmission of IPv6 Packets over Frame Relay Networks Specification

RFC 3152

Delegation of IP6.ARPA

RFC 3162

RADIUS and IPv6

RFC 3513

Internet Protocol Version 6 (IPv6) Addressing Architecture

RFC 3596

DNS Extensions to Support IP version 6

Technical Assistance

Description

Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

http://www.cisco.com/cisco/web/support/index.html

Feature Information for Implementing IPv6 Addressing and Basic Connectivity

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Table 5. Feature Information for Implementing IPv6 Addressing and Basic Connectivity

Feature Name

Releases

Feature Information

IPv6--Base Protocols High Availability

Cisco IOS XE Release 2.1

IPv6 Neighbor Discovery supports SSO.

IPv6--ICMPv6

Cisco IOS XE Release 2.1

ICMP for IPv6 generates error messages, such as ICMP destination unreachable messages, and informational messages, such as ICMP echo request and reply messages. Additionally, ICMP packets in IPv6 are used in the IPv6 Neighbor Discovery process, path MTU discovery, and the MLD protocol for IPv6.

IPv6--ICMPv6 Redirect

Cisco IOS XE Release 2.1

A value of 137 in the Type field of the ICMP packet header identifies an IPv6 neighbor redirect message. Routers send neighbor redirect messages to inform hosts of better first-hop nodes on the path to a destination.

IPv6--ICMP Rate Limiting

Cisco IOS XE Release 2.1

The IPv6 ICMP rate limiting feature implements a token bucket algorithm for limiting the rate at which IPv6 ICMP error messages are sent out on the network.

IPv6--IPv6 Default Router Preferences

Cisco IOS XE Release 2.1

The DRP extension provides a coarse preference metric (low, medium, or high) for default routers.

IPv6--IPv6 MTU Path Discovery

Cisco IOS XE Release 2.1

Path MTU discovery in IPv6 allows a host to dynamically discover and adjust to differences in the MTU size of every link along a given data path.

IPv6--IPv6 Neighbor Discovery

Cisco IOS XE Release 2.1

The IPv6 Neighbor Discovery process uses ICMP messages and solicited-node multicast addresses to determine the link-layer address of a neighbor on the same network (local link), verify the reachability of a neighbor, and track neighboring routers.

IPv6--IPv6 Neighbor Discovery Duplicate Address Detection

Cisco IOS XE Release 2.1

IPv6 Neighbor Discovery duplicate address detection is performed first on a new, link-local IPv6 address before the address is assigned to an interface (the new address remains in a tentative state while duplicate address detection is performed).

IPv6--IPv6 Stateless Autoconfiguration

Cisco IOS XE Release 2.1

The IPv6 stateless autoconfiguration feature can be used to manage link, subnet, and site addressing changes.

IPv6--Per-Interface Neighbor Discovery Cache Limit

Cisco IOS XE Release 2.6

The per-interface Neighbor Discovery cache limit feature provides the ability to limit the number of Neighbor Discovery cache entries on a per interface basis. The following sections provide information about this feature:

The following commands were introduced or modified for this feature:

ipv6 nd cache interface-limit (global) , ipv6 nd cache interface-limit (interface) , show ipv6 neighbors .

IPv6--IPv6 Static Cache Entry for Neighbor Discovery

Cisco IOS XE Release 2.1

The IPv6 static cache entry for Neighbor Discovery feature allows static entries to be made in the IPv6 neighbor cache.

IPv6 Data Link--Cisco High-Level Data Link Control (HDLC)

Cisco IOS XE Release 2.1

In IPv6 networks, a data link is a network sharing a particular link-local prefix. HDLC is a type of data link supported for IPv6.

IPv6 Data Link--Fast Ethernet

Cisco IOS XE Release 2.1

In IPv6 networks, a data link is a network sharing a particular link-local prefix. Fast Ethernet data links supported for IPv6.

IPv6 Data Link--FDDI

Cisco IOS XE Release 2.1

In IPv6 networks, a data link is a network sharing a particular link-local prefix. FDDI is a type of data link supported for IPv6.

IPv6 Data Link--Frame Relay PVC

Cisco IOS XE Release 2.1

In IPv6 networks, a data link is a network sharing a particular link-local prefix. Frame relay PVC is a type of data link supported for IPv6.

IPv6 Data Link--PPP Service over Packet over SONET, ISDN, and Serial (Synchronous and Asynchronous) Interfaces

Cisco IOS XE Release 2.1

In IPv6 networks, a data link is a network sharing a particular link-local prefix. PPP service over Packet over SONET, ISDN, and serial interfaces is a type of data link supported for IPv6.

IPv6 Data Link--VLANs Using IEEE 802.1Q Encapsulation

Cisco IOS XE Release 2.1

In IPv6 networks, a data link is a network sharing a particular link-local prefix. VLANs using IEEE 802.1Q encapsulation is a type of data link supported for IPv6.

IPv6 Services--AAAA DNS Lookups over an IPv4 Transport

Cisco IOS XE Release 2.1

IPv6 basic connectivity can be enhanced by configuring support for AAAA record types in the DNS name-to-address and address-to-name lookup processes.

IPv6 Services--Cisco Discovery Protocol--IPv6 Address Family Support for Neighbor Information

Cisco IOS XE Release 2.1

The Cisco Discovery Protocol IPv6 address support for neighbor information feature adds the ability to transfer IPv6 addressing information between two Cisco devices.

IPv6 Services--DNS Lookups over an IPv6 Transport

Cisco IOS XE Release 2.1

IPv6 supports DNS record types that are supported in the DNS name-to-address and address-to-name lookup processes.

IPv6 Switching--Cisco Express Forwarding and Distributed Cisco Express Forwarding Support

Cisco IOS XE Release 2.1

Cisco Express Forwarding for IPv6 is advanced, Layer 3 IP switching technology for the forwarding of IPv6 packets. Distributed Cisco Express Forwarding for IPv6 performs the same functions as CEFv6 but for distributed architecture platforms.

SSO/ISSU Support for per-User IPv6 ACL for PPP Sessions

Cisco IOS XE 3.2.1S

Reproducing IPv6 ACLs on the active RP to the standby RP provides a consistent SSO and ISSU experience for active sessions.

Unicast Reverse Path Forwarding for IPv6

Cisco IOS XE Release 2.1

The Unicast RPF feature mitigates problems caused by malformed or forged (spoofed) IPv6 source addresses that pass through an IPv6 router.