Information About Configuring IPv6 Unicast Routing
This chapter describes how to configure IPv6 unicast routing on the switch.
Understanding IPv6
IPv4 users can move to IPv6 and receive services such as end-to-end security, quality of service (QoS), and globally unique addresses. The IPv6 address space reduces the need for private addresses and Network Address Translation (NAT) processing by border routers at network edges.
For information about how Cisco Systems implements IPv6, go to:
http://www.cisco.com/en/US/products/ps6553/products_ios_technology_home.html
For information about IPv6 and other features in this chapter
-
See the Cisco IOS IPv6 Configuration Library.
-
Use the Search field on Cisco.com to locate the Cisco IOS software documentation. For example, if you want information about static routes, you can enter Implementing Static Routes for IPv6 in the search field to learn about static routes.
IPv6 Addresses
The switch supports only IPv6 unicast addresses. It does not support site-local unicast addresses, or anycast addresses.
The IPv6 128-bit addresses are represented as a series of eight 16-bit hexadecimal fields separated by colons in the format: n:n:n:n:n:n:n:n. This is an example of an IPv6 address:
2031:0000:130F:0000:0000:09C0:080F:130B
For easier implementation, leading zeros in each field are optional. This is the same address without leading zeros:
2031:0:130F:0:0:9C0:80F:130B
You can also use two colons (::) to represent successive hexadecimal fields of zeros, but you can use this short version only once in each address:
2031:0:130F::09C0:080F:130B
For more information about IPv6 address formats, address types, and the IPv6 packet header, see the http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipv6_basic/configuration/xe-3e/ip6b-xe-3e-book.html of Cisco IOS IPv6 Configuration Library on Cisco.com.
In the “Information About Implementing Basic Connectivity for IPv6” chapter, these sections apply to the switch:
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IPv6 Address Formats
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IPv6 Address Type: Unicast
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IPv6 Address Type: Multicast
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IPv6 Address Output Display
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Simplified IPv6 Packet Header
Supported IPv6 Unicast Routing Features
These sections describe the IPv6 protocol features supported by the switch:
The switch provides IPv6 routing capability over Routing Information Protocol (RIP) for IPv6, and Open Shortest Path First (OSPF) Version 3 Protocol. It supports up to 16 equal-cost routes and can simultaneously forward IPv4 and IPv6 frames at line rate.
128-Bit Wide Unicast Addresses
The switch supports aggregatable global unicast addresses and link-local unicast addresses. It does not support site-local unicast addresses.
-
Aggregatable global unicast addresses are IPv6 addresses from the aggregatable global unicast prefix. The address structure enables strict aggregation of routing prefixes and limits the number of routing table entries in the global routing table. These addresses are used on links that are aggregated through organizations and eventually to the Internet service provider.
These addresses are defined by a global routing prefix, a subnet ID, and an interface ID. Current global unicast address allocation uses the range of addresses that start with binary value 001 (2000::/3). Addresses with a prefix of 2000::/3(001) through E000::/3(111) must have 64-bit interface identifiers in the extended unique identifier (EUI)-64 format.
-
Link local unicast addresses can be automatically configured on any interface by using the link-local prefix FE80::/10(1111 1110 10) and the interface identifier in the modified EUI format. Link-local addresses are used in the neighbor discovery protocol (NDP) and the stateless autoconfiguration process. Nodes on a local link use link-local addresses and do not require globally unique addresses to communicate. IPv6 routers do not forward packets with link-local source or destination addresses to other links.
For more information, see the section about IPv6 unicast addresses in the “Implementing IPv6 Addressing and Basic Connectivity” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.
DNS for IPv6
IPv6 supports Domain Name System (DNS) record types in the DNS name-to-address and address-to-name lookup processes. The DNS AAAA resource record types support IPv6 addresses and are equivalent to an A address record in IPv4. The switch supports DNS resolution for IPv4 and IPv6.
Path MTU Discovery for IPv6 Unicast
The switch supports advertising the system maximum transmission unit (MTU) to IPv6 nodes and path MTU discovery. Path MTU discovery allows a host to dynamically discover and adjust to differences in the MTU size of every link along a given data path. In IPv6, if a link along the path is not large enough to accommodate the packet size, the source of the packet handles the fragmentation.
ICMPv6
The Internet Control Message Protocol (ICMP) in IPv6 generates error messages, such as ICMP destination unreachable messages, to report errors during processing and other diagnostic functions. In IPv6, ICMP packets are also used in the neighbor discovery protocol and path MTU discovery.
Neighbor Discovery
The switch supports NDP for IPv6, a protocol running on top of ICMPv6, and static neighbor entries for IPv6 stations that do not support NDP. 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), to verify the reachability of the neighbor, and to keep track of neighboring routers.
The switch supports ICMPv6 redirect for routes with mask lengths less than 64 bits. ICMP redirect is not supported for host routes or for summarized routes with mask lengths greater than 64 bits.
Neighbor discovery throttling ensures that the switch CPU is not unnecessarily burdened while it is in the process of obtaining the next hop forwarding information to route an IPv6 packet. The switch drops any additional IPv6 packets whose next hop is the same neighbor that the switch is actively trying to resolve. This drop avoids further load on the CPU.
Default Router Preference
The switch supports IPv6 default router preference (DRP), an extension in router advertisement messages. DRP improves the ability of a host to select an appropriate router, especially when the host is multihomed and the routers are on different links. The switch does not support the Route Information Option in RFC 4191.
An IPv6 host maintains a default router list from which it selects a router for traffic to offlink destinations. The selected router for a destination is then cached in the destination cache. NDP for IPv6 specifies that routers that are reachable or probably reachable are preferred over routers whose reachability is unknown or suspect. For reachable or probably reachable routers, NDP can either select the same router every time or cycle through the router list. By using DRP, you can configure an IPv6 host to prefer one router over another, provided both are reachable or probably reachable.
For more information about DRP for IPv6, see the Cisco IOS IPv6 Configuration Library on Cisco.com.
IPv6 Stateless Autoconfiguration and Duplicate Address Detection
The switch uses stateless autoconfiguration to manage link, subnet, and site addressing changes, such as management of host and mobile IP addresses. A host autonomously configures its own link-local address, and booting nodes send router solicitations to request router advertisements for configuring interfaces.
For more information about autoconfiguration and duplicate address detection, see the “Implementing IPv6 Addressing and Basic Connectivity” chapter of Cisco IOS IPv6 Configuration Library on Cisco.com.
IPv6 Applications
The switch has IPv6 support for these applications:
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Ping, traceroute, Telnet, and TFTP
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FTP (This is supported only on Cisco Catalyst 9500 Series Switches - High Performance)
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Secure Shell (SSH) over an IPv6 transport
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HTTP server access over IPv6 transport
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DNS resolver for AAAA over IPv4 transport
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Cisco Discovery Protocol (CDP) support for IPv6 addresses
For more information about managing these applications, see the Cisco IOS IPv6 Configuration Library on Cisco.com.
DHCP for IPv6 Address Assignment
DHCPv6 enables DHCP servers to pass configuration parameters, such as IPv6 network addresses, to IPv6 clients. The address assignment feature manages non-duplicate address assignment in the correct prefix based on the network where the host is connected. Assigned addresses can be from one or multiple prefix pools. Additional options, such as default domain and DNS name-server address, can be passed back to the client. Address pools can be assigned for use on a specific interface, on multiple interfaces, or the server can automatically find the appropriate pool.
For more information and to configure these features, see the Cisco IOS IPv6 Configuration Guide.
This document describes only the DHCPv6 address assignment. For more information about configuring the DHCPv6 client, server, or relay agent functions, see the “Implementing DHCP for IPv6” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.
Static Routes for IPv6
Static routes are manually configured and define an explicit route between two networking devices. Static routes are useful for smaller networks with only one path to an outside network or to provide security for certain types of traffic in a larger network.
For more information about static routes, see the “Implementing Static Routes for IPv6” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.
Static Route Support for Object Tracking
The IPv6 Static Route Support for Object Tracking feature allows an IPv6 static route to be associated with a tracked-object. For more information, see Cisco IOS IPv6 Configuration Library on Cisco.com.
Policy-Based Routing for IPv6
Policy-based routing (PBR) gives you a flexible means of routing packets by allowing you to configure a defined policy for traffic flows, which lessens reliance on routes derived from routing protocols. Therefore, PBR gives you more control over routing by extending and complementing the existing mechanisms provided by routing protocols. PBR allows you to set the IPv6 precedence. For a simple policy, you can use any one of these tasks; for a complex policy, you can use all of them. It also allows you to specify a path for certain traffic, such as priority traffic over a high-cost link.
PBR for IPv6 may be applied to both forwarded and originated IPv6 packets. For forwarded packets, PBR for IPv6 will be implemented as an IPv6 input interface feature, supported in the following forwarding paths:
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Process
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Cisco Express Forwarding (formerly known as CEF)
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Distributed Cisco Express Forwarding
Policies can be based on the IPv6 address, port numbers, protocols, or packet size.
PBR allows you to perform the following tasks:
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Classify traffic based on extended access list criteria. Access lists, then, establish the match criteria.
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Set IPv6 precedence bits, giving the network the ability to enable differentiated classes of service.
Note
This is not supported on Cisco Catalyst 9500 Series Switches - High Performance
-
Route packets to specific traffic-engineered paths; you might need to route them to allow a specific quality of service (QoS) through the network.
PBR allows you to classify and mark packets at the edge of the network. PBR marks a packet by setting precedence value. The precedence value can be used directly by devices in the network core to apply the appropriate QoS to a packet, which keeps packet classification at your network edge.
RIP for IPv6
Routing Information Protocol (RIP) for IPv6 is a distance-vector protocol that uses hop count as a routing metric. It includes support for IPv6 addresses and prefixes and the all-RIP-routers multicast group address FF02::9 as the destination address for RIP update messages.
For more information about RIP for IPv6, see the “Implementing RIP for IPv6” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.
OSPF for IPv6
The switch supports Open Shortest Path First (OSPF) for IPv6, a link-state protocol for IP. For more information, seeCisco IOS IPv6 Configuration Library on Cisco.com.
IS-IS for IPv6
The switch supports Integrated Intermediate System-to-Intermediate System (IS-IS) for IPv6, an Open Systems Interconnection (OSI) hierarchical routing protocol. For more information, see Cisco IOS IPv6 Configuration Library on Cisco.com.
EIGRP IPv6
Switches support the Enhanced Interior Gateway Routing Protocol (EIGRP) for IPv6. It is configured on the interfaces on which it runs and does not require a global IPv6 address. Switches running IP Lite only support EIGRPv6 stub routing.
Before running, an instance of EIGRP IPv6 requires an implicit or explicit router ID. An implicit router ID is derived from a local IPv6 address, so any IPv6 node always has an available router ID. However, EIGRP IPv6 might be running in a network with only IPv6 nodes and therefore might not have an available IPv6 router ID.
For more information about EIGRP for IPv6, see the “Implementing EIGRP for IPv6” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.
EIGRPv6 Stub Routing
The EIGRPv6 stub routing feature, reduces resource utilization by moving routed traffic closer to the end user.
In a network using EIGRPv6 stub routing, the only allowable route for IPv6 traffic to the user is through a switch that is configured with EIGRPv6 stub routing. The switch sends the routed traffic to interfaces that are configured as user interfaces or are connected to other devices.
When using EIGRPv6 stub routing, you need to configure the distribution and remote routers to use EIGRPv6 and to configure only the switch as a stub. Only specified routes are propagated from the switch. The switch responds to all queries for summaries, connected routes, and routing updates.
Any neighbor that receives a packet informing it of the stub status does not query the stub router for any routes, and a router that has a stub peer does not query that peer. The stub router depends on the distribution router to send the proper updates to all peers.
In the figure given below, switch B is configured as an EIGRPv6 stub router. Switches A and C are connected to the rest of the WAN. Switch B advertises connected, static, redistribution, and summary routes to switch A and C. Switch B does not advertise any routes learned from switch A (and the reverse).
![](/c/dam/en/us/td/i/100001-200000/140001-150000/145001-146000/145776.ps/_jcr_content/renditions/145776.jpg)
For more information about EIGRPv6 stub routing, see “Implementing EIGRP for IPv6” section of the Cisco IOS IP Configuration Guide, Volume 2 of 3: Routing Protocols, Release 12.4.
SNMP and Syslog Over IPv6
To support both IPv4 and IPv6, IPv6 network management requires both IPv6 and IPv4 transports. Syslog over IPv6 supports address data types for these transports.
SNMP and syslog over IPv6 provide these features:
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Support for both IPv4 and IPv6
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IPv6 transport for SNMP and to modify the SNMP agent to support traps for an IPv6 host
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SNMP- and syslog-related MIBs to support IPv6 addressing
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Configuration of IPv6 hosts as trap receivers
For support over IPv6, SNMP modifies the existing IP transport mapping to simultaneously support IPv4 and IPv6. These SNMP actions support IPv6 transport management:
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Opens User Datagram Protocol (UDP) SNMP socket with default settings
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Provides a new transport mechanism called SR_IPV6_TRANSPORT
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Sends SNMP notifications over IPv6 transport
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Supports SNMP-named access lists for IPv6 transport
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Supports SNMP proxy forwarding using IPv6 transport
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Verifies SNMP Manager feature works with IPv6 transport
For information on SNMP over IPv6, including configuration procedures, see the “Managing Cisco IOS Applications over IPv6” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.
For information about syslog over IPv6, including configuration procedures, see the “Implementing IPv6 Addressing and Basic Connectivity” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.
HTTP(S) Over IPv6
The HTTP client sends requests to both IPv4 and IPv6 HTTP servers, which respond to requests from both IPv4 and IPv6 HTTP clients. URLs with literal IPv6 addresses must be specified in hexadecimal using 16-bit values between colons.
The accept socket call chooses an IPv4 or IPv6 address family. The accept socket is either an IPv4 or IPv6 socket. The listening socket continues to listen for both IPv4 and IPv6 signals that indicate a connection. The IPv6 listening socket is bound to an IPv6 wildcard address.
The underlying TCP/IP stack supports a dual-stack environment. HTTP relies on the TCP/IP stack and the sockets for processing network-layer interactions.
Basic network connectivity (ping ) must exist between the client and the server hosts before HTTP connections can be made.
For more information, see the “Managing Cisco IOS Applications over IPv6” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.
Tool command language (TCL)
Tool command language (TCL) is used in Cisco software for IPv6 to support features such as embedded syslog manager (ESM), embedded event manager (EEM), interactive voice response (IVR), and tclsh parser mode. TCL supports both initiating (client) and listening (server) sockets.
Unsupported IPv6 Unicast Routing Features
The switch does not support these IPv6 features:
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IPv6 packets destined to site-local addresses
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Tunneling protocols, such as IPv4-to-IPv6 or IPv6-to-IPv4
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The switch as a tunnel endpoint supporting IPv4-to-IPv6 or IPv6-to-IPv4 tunneling protocols
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IPv6 Web Cache Communication Protocol (WCCP)
IPv6 Feature Limitations
Because IPv6 is implemented in switch hardware, some limitations occur due to the IPv6 compressed addresses in the hardware memory. These hardware limitations result in some loss of functionality and limits some features.
These are feature limitations.
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The switch cannot forward SNAP-encapsulated IPv6 packets in hardware. They are forwarded in software.
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The switch cannot apply QoS classification on source-routed IPv6 packets in hardware.
IPv6 and Switch Stacks
![]() Note |
Switch stacks are not supported on Cisco Catalyst 9500 Series Switches - High Performance. |
The switch supports IPv6 forwarding across the stack and IPv6 host functionality on the stack master. The stack master runs the IPv6 unicast routing protocols and computes the routing tables. They receive the tables and create hardware IPv6 routes for forwarding. The stack master also runs all IPv6 applications.
If a new switch becomes the stack master, it recomputes the IPv6 routing tables and distributes them to the member switches. While the new stack master is being elected and is resetting, the switch stack does not forward IPv6 packets. The stack MAC address changes, which also changes the IPv6 address. When you specify the stack IPv6 address with an extended unique identifier (EUI) by using the ipv6 address ipv6-prefix/prefix length eui-64 interface configuration command, the address is based on the interface MAC address. See the Configuring IPv6 Addressing and Enabling IPv6 Routing .
If you configure the persistent MAC address feature on the stack and the stack master changes, the stack MAC address does not change for approximately 4 minutes.
These are the functions of IPv6 stack master and members:
- Stack master:
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runs IPv6 routing protocols
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generates routing tables
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distributes routing tables to stack members that use distributed Cisco Express Forwarding for IPv6
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runs IPv6 host functionality and IPv6 applications
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- Stack member:
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receives Cisco Express Forwarding for IPv6 routing tables from the stack master
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programs the routes into hardware
Note
IPv6 packets are routed in hardware across the stack if the packet does not have exceptions (IPv6 Options) and the switches in the stack have not run out of hardware resources.
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flushes the Cisco Express Forwarding for IPv6 tables on master re-election
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Default IPv6 Configuration
Feature |
Default Setting |
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SDM template |
Default is core template |
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IPv6 routing |
Disabled globally and on all interfaces |
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Cisco Express Forwarding for IPv6 or distributed Cisco Express Forwarding for IPv6 |
Disabled (IPv4 Cisco Express Forwarding and distributed Cisco Express Forwarding are enabled by default)
|
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IPv6 addresses |
None configured |
Configuring IPv6 Addressing and Enabling IPv6 Routing
This section describes how to assign IPv6 addresses to individual Layer 3 interfaces and to globally forward IPv6 traffic on the switch.
Before configuring IPv6 on the switch, consider these guidelines:
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Not all features discussed in this chapter are supported by the switch. See the Unsupported IPv6 Unicast Routing Features.
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In the ipv6 address interface configuration command, you must enter the ipv6-address and ipv6-prefix variables with the address specified in hexadecimal using 16-bit values between colons. The prefix-length variable (preceded by a slash [/]) is a decimal value that shows how many of the high-order contiguous bits of the address comprise the prefix (the network portion of the address).
To forward IPv6 traffic on an interface, you must configure a global IPv6 address on that interface. Configuring an IPv6 address on an interface automatically configures a link-local address and activates IPv6 for the interface. The configured interface automatically joins these required multicast groups for that link:
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solicited-node multicast group FF02:0:0:0:0:1:ff00::/104 for each unicast address assigned to the interface (this address is used in the neighbor discovery process.)
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all-nodes link-local multicast group FF02::1
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all-routers link-local multicast group FF02::2
To remove an IPv6 address from an interface, use the no ipv6 address ipv6-prefix/prefix length eui-64 or no ipv6 address ipv6-address link-local interface configuration command. To remove all manually configured IPv6 addresses from an interface, use the no ipv6 address interface configuration command without arguments. To disable IPv6 processing on an interface that has not been explicitly configured with an IPv6 address, use the no ipv6 enable interface configuration command. To globally disable IPv6 routing, use the no ipv6 unicast-routing global configuration command.
For more information about configuring IPv6 routing, see the “Implementing Addressing and Basic Connectivity for IPv6” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.
To assign an IPv6 address to a Layer 3 interface and enable IPv6 routing, perform this procedure:
Procedure
Command or Action | Purpose | |
---|---|---|
Step 1 |
enable Example:
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Enables privileged EXEC mode. Enter your password if prompted. |
Step 2 |
configure terminal Example:
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Enters global configuration mode. |
Step 3 |
sdm prefer {core | distribution | nat | sda } Example:
|
Select an SDM template:
|
Step 4 |
end Example:
|
Returns to privileged EXEC mode. |
Step 5 |
reload Example:
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Reloads the operating system. |
Step 6 |
configure terminal Example:
|
Enters global configuration mode after the switch reloads. |
Step 7 |
interface interface-id Example:
|
Enters interface configuration mode, and specifies the Layer 3 interface to configure. The interface can be a physical interface, a switch virtual interface (SVI), or a Layer 3 EtherChannel. |
Step 8 |
no switchport Example:
|
Removes the interface from Layer 2 configuration mode (if it is a physical interface). |
Step 9 |
Use one of the following:
Example:
|
|
Step 10 |
exit Example:
|
Returns to global configuration mode. |
Step 11 |
ip routing Example:
|
Enables IP routing on the switch. |
Step 12 |
ipv6 unicast-routing Example:
|
Enables forwarding of IPv6 unicast data packets. |
Step 13 |
end Example:
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Returns to privileged EXEC mode. |
Step 14 |
show ipv6 interface interface-id Example:
|
Verifies your entries. |
Step 15 |
copy running-config startup-config Example:
|
(Optional) Saves your entries in the configuration file. |
Configuring IPv4 and IPv6 Protocol Stacks
To configure a Layer 3 interface to support both IPv4 and IPv6 and to enable IPv6 routing, perform this procedure:.
![]() Note |
To disable IPv6 processing on an interface that has not been configured with an IPv6 address, use the no ipv6 enable interface configuration command. |
SUMMARY STEPS
- enable
- configure terminal
- ip routing
- ipv6 unicast-routing
- interface interface-id
- no switchport
- ip address ip-address mask [secondary ]
- Use one of the following:
- ipv6 address ipv6-prefix/prefix length eui-64
- ipv6 address ipv6-address/prefix length
- ipv6 address ipv6-address link-local
- ipv6 enable
- ipv6 address WORD
- ipv6 address autoconfig
- ipv6 address dhcp
- end
- Use one of the following:
- show interface interface-id
- show ip interface interface-id
- show ipv6 interface interface-id
- copy running-config startup-config
DETAILED STEPS
Command or Action | Purpose | |||
---|---|---|---|---|
Step 1 |
enable Example:
|
Enables privileged EXEC mode. Enter your password if prompted. |
||
Step 2 |
configure terminal Example:
|
Enters global configuration mode. |
||
Step 3 |
ip routing Example:
|
Enables routing on the switch. |
||
Step 4 |
ipv6 unicast-routing Example:
|
Enables forwarding of IPv6 data packets on the switch. |
||
Step 5 |
interface interface-id Example:
|
Enters interface configuration mode, and specifies the Layer 3 interface to configure. |
||
Step 6 |
no switchport Example:
|
Removes the interface from Layer 2 configuration mode (if it is a physical interface). |
||
Step 7 |
ip address ip-address mask [secondary ] Example:
|
Specifies a primary or secondary IPv4 address for the interface. |
||
Step 8 |
Use one of the following:
|
|
||
Step 9 |
end Example:
|
Returns to privileged EXEC mode. |
||
Step 10 |
Use one of the following:
|
Verifies your entries. |
||
Step 11 |
copy running-config startup-config Example:
|
(Optional) Saves your entries in the configuration file. |
Configuring Default Router Preference
Router advertisement messages are sent with the default router preference (DRP) configured by the ipv6 nd router-preference interface configuration command. If no DRP is configured, RAs are sent with a medium preference.
A DRP is useful when two routers on a link might provide equivalent, but not equal-cost routing, and policy might dictate that hosts should prefer one of the routers.
For more information about configuring DRP for IPv6, see the “Implementing IPv6 Addresses and Basic Connectivity” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.
To configure a DRP for a router on an interface, perform this procedure:
Procedure
Command or Action | Purpose | |
---|---|---|
Step 1 |
enable Example:
|
Enables privileged EXEC mode. Enter your password if prompted. |
Step 2 |
configure terminal Example:
|
Enters global configuration mode. |
Step 3 |
interface interface-id Example:
|
Enters interface configuration mode and identifies the Layer 3 interface on which you want to specify the DRP. |
Step 4 |
ipv6 nd router-preference {high | medium | low } Example:
|
Specifies a DRP for the router on the switch interface. |
Step 5 |
end Example:
|
Returns to privileged EXEC mode. |
Step 6 |
show ipv6 interface Example:
|
Verifies the configuration. |
Step 7 |
copy running-config startup-config Example:
|
(Optional) Saves your entries in the configuration file. |
Configuring IPv6 ICMP Rate Limiting
ICMP rate limiting is enabled by default with a default interval between error messages of 100 milliseconds and a bucket size (maximum number of tokens to be stored in a bucket) of 10.
To change the ICMP rate-limiting parameters, perform this procedure:
Procedure
Command or Action | Purpose | |
---|---|---|
Step 1 |
enable Example:
|
Enables privileged EXEC mode. Enter your password if prompted. |
Step 2 |
configure terminal Example:
|
Enters global configuration mode. |
Step 3 |
ipv6 icmp error-interval interval [bucketsize] Example:
|
Configures the interval and bucket size for IPv6 ICMP error messages:
|
Step 4 |
end Example:
|
Returns to privileged EXEC mode. |
Step 5 |
show ipv6 interface [interface-id] Example:
|
Verifies your entries. |
Step 6 |
copy running-config startup-config Example:
|
(Optional) Saves your entries in the configuration file. |
Configuring Cisco Express Forwarding and distributed Cisco Express Forwarding for IPv6
Cisco Express Forwarding is a Layer 3 IP switching technology to improve network performance. Cisco Express Forwarding implements an advanced IP look-up and forwarding algorithm to deliver maximum Layer 3 switching performance. It is less CPU-intensive than fast-switching route-caching, allowing more CPU processing power to be dedicated to packet forwarding. In a switch stack, the hardware uses distributed Cisco Express Forwarding in the stack. IPv4 Cisco Express Forwarding and distributed Cisco Express Forwarding are enabled by default. IPv6 Cisco Express Forwarding and distributed Cisco Express Forwarding are disabled by default, but automatically enabled when you configure IPv6 routing.
IPv6 Cisco Express Forwarding and distributed Cisco Express Forwarding are automatically disabled when IPv6 routing is unconfigured. IPv6 Cisco Express Forwarding and distributed Cisco Express Forwarding cannot disabled through configuration. You can verify the IPv6 state by entering the show ipv6 cef privileged EXEC command.
To route IPv6 unicast packets, you must first globally configure forwarding of IPv6 unicast packets by using the ipv6 unicast-routing global configuration command, and you must configure an IPv6 address and IPv6 processing on an interface by using the ipv6 address interface configuration command.
For more information about configuring Cisco Express Forwarding and distributed Cisco Express Forwarding, see Cisco IOS IPv6 Configuration Library on Cisco.com.
Configuring Static Routing for IPv6
For more information about configuring static IPv6 routing, see the “Implementing Static Routes for IPv6” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.
To configure static IPv6 routing, perform this procedure:
Before you begin
You must enable routing by using the ip routing global configuration command, enable the forwarding of IPv6 packets by using the ipv6 unicast-routing global configuration command, and enable IPv6 on at least one Layer 3 interface by configuring an IPv6 address on the interface.
Procedure
Command or Action | Purpose | |||
---|---|---|---|---|
Step 1 |
enable Example:
|
Enables privileged EXEC mode. Enter your password if prompted. |
||
Step 2 |
configure terminal Example:
|
Enters global configuration mode. |
||
Step 3 |
ipv6 route ipv6-prefix/prefix length {ipv6-address | interface-id [ipv6-address]} [administrative distance] Example:
|
Configures a static IPv6 route.
|
||
Step 4 |
end Example:
|
Returns to privileged EXEC mode. |
||
Step 5 |
Use one of the following:
Example:
or
|
Verifies your entries by displaying the contents of the IPv6 routing table.
|
||
Step 6 |
copy running-config startup-config Example:
|
(Optional) Saves your entries in the configuration file. |
Enabling IPv6 PBR on an Interface
To enable Policy-Based Routing (PBR) for IPv6, you must create a route map that specifies the packet match criteria and desired policy-route action. Then you associate the route map on the required interface. All packets arriving on the specified interface that match the match clauses will be subject to PBR.
In PBR, the set vrf command decouples the virtual routing and forwarding (VRF) instance and interface association and allows the selection of a VRF based on access control list (ACL)-based classification using existing PBR or route-map configurations. It provides a single router with multiple routing tables and the ability to select routes based on ACL classification. The router classifies packets based on ACL, selects a routing table, looks up the destination address, and then routes the packet.
To enable PBR for IPv6, perform this procedure:
SUMMARY STEPS
- enable
- configure terminal
- route-map map-tag [permit | deny ] [sequence-number ]
- Do one of the following:
- match length minimum-length maximum-length
- match ipv6 address {prefix-list prefix-list-name | access-list-name }
- Do one of the following:
- set ipv6 next-hop global-ipv6-address [global-ipv6-address... ]
- set ipv6 default next-hop global-ipv6-address [global-ipv6-address... ]
- exit
- interface type number
- ipv6 policy route-map route-map-name
- end
DETAILED STEPS
Command or Action | Purpose | |
---|---|---|
Step 1 |
enable Example:
|
Enables privileged EXEC mode. Enter your password if prompted. |
Step 2 |
configure terminal Example:
|
Enters global configuration mode. |
Step 3 |
route-map map-tag [permit | deny ] [sequence-number ] Example:
|
Defines the conditions for redistributing routes from one routing protocol into another, or enables policy routing, and enters route-map configuration mode. |
Step 4 |
Do one of the following:
Example:
Example:
|
Specifies the match criteria.
|
Step 5 |
Do one of the following:
Example:
Example:
|
Specifies the action or actions to take on the packets that match the criteria.
|
Step 6 |
exit Example:
|
Exits route-map configuration mode and returns to global configuration mode. |
Step 7 |
interface type number Example:
|
Specifies an interface type and number, and places the router in interface configuration mode. |
Step 8 |
ipv6 policy route-map route-map-name Example:
|
Identifies a route map to use for IPv6 PBR on an interface. |
Step 9 |
end Example:
|
Exits interface configuration mode and returns to privileged EXEC mode. |
Enabling Local PBR for IPv6
Packets that are generated by the device are not normally policy routed. Perform this task to enable local IPv6 policy-based routing (PBR) for such packets, indicating which route map the device should use.
To enable Local PBR for IPv6, perform this procedure:
SUMMARY STEPS
- enable
- configure terminal
- ipv6 local policy route-map route-map-name
- end
DETAILED STEPS
Command or Action | Purpose | |
---|---|---|
Step 1 |
enable Example:
|
Enables privileged EXEC mode. Enter your password if prompted. |
Step 2 |
configure terminal Example:
|
Enters global configuration mode. |
Step 3 |
ipv6 local policy route-map route-map-name Example:
|
Configures IPv6 PBR for packets generated by the device. |
Step 4 |
end Example:
|
Returns to privileged EXEC mode. |
Configuring RIP for IPv6
For more information about configuring RIP routing for IPv6, see the “Implementing RIP for IPv6” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com,
To configure RIP routing for IPv6, perform this procedure:
Before you begin
Before configuring the switch to run IPv6 RIP, you must enable routing by using the ip routing global configuration command, enable the forwarding of IPv6 packets by using the ipv6 unicast-routing global configuration command, and enable IPv6 on any Layer 3 interfaces on which IPv6 RIP is to be enabled.
Procedure
Command or Action | Purpose | |||
---|---|---|---|---|
Step 1 |
enable Example:
|
Enables privileged EXEC mode. Enter your password if prompted. |
||
Step 2 |
configure terminal Example:
|
Enters global configuration mode. |
||
Step 3 |
ipv6 router rip name Example:
|
Configures an IPv6 RIP routing process, and enters router configuration mode for the process. |
||
Step 4 |
maximum-paths number-paths Example:
|
(Optional) Define the maximum number of equal-cost routes that IPv6 RIP can support. The range is from 1 to 32, and the default is 16 routes. |
||
Step 5 |
exit Example:
|
Returns to global configuration mode. |
||
Step 6 |
interface interface-id Example:
|
Enters interface configuration mode, and specifies the Layer 3 interface to configure. |
||
Step 7 |
ipv6 rip name enable Example:
|
Enables the specified IPv6 RIP routing process on the interface. |
||
Step 8 |
ipv6 rip name default-information {only | originate } Example:
|
(Optional) Originates the IPv6 default route (::/0) into the RIP routing process updates sent from the specified interface.
|
||
Step 9 |
end Example:
|
Returns to privileged EXEC mode. |
||
Step 10 |
Use one of the following:
Example:
or
|
|
||
Step 11 |
copy running-config startup-config Example:
|
(Optional) Saves your entries in the configuration file. |
Configuring OSPF for IPv6
For more information about configuring OSPF routing for IPv6, see the “Implementing OSPF for IPv6” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.
To configure OSPF routing for IPv6, perform this procedure:
Before you begin
You can customize OSPF for IPv6 for your network. However, the defaults for OSPF in IPv6 are set to meet the requirements of most customers and features.
Follow these guidelines:
-
Be careful when changing the defaults for IPv6 commands. Changing the defaults might adversely affect OSPF for the IPv6 network.
-
Before you enable IPv6 OSPF on an interface, you must enable routing by using the ip routing global configuration command, enable the forwarding of IPv6 packets by using the ipv6 unicast-routing global configuration command, and enable IPv6 on Layer 3 interfaces on which you are enabling IPv6 OSPF.
Procedure
Command or Action | Purpose | |
---|---|---|
Step 1 |
enable Example:
|
Enables privileged EXEC mode. Enter your password if prompted. |
Step 2 |
configure terminal Example:
|
Enters global configuration mode. |
Step 3 |
ipv6 router ospf process-id Example:
|
Enables OSPF router configuration mode for the process. The process ID is the number assigned administratively when enabling the OSPF for IPv6 routing process. It is locally assigned and can be a positive integer from 1 to 65535. |
Step 4 |
area area-id range {ipv6-prefix/prefix length} [advertise | not-advertise ] [cost cost] Example:
|
(Optional) Consolidates and summarizes routes at an area boundary.
|
Step 5 |
maximum paths number-paths Example:
|
(Optional) Defines the maximum number of equal-cost routes to the same destination that IPv6 OSPF should enter in the routing table. The range is from 1 to 32, and the default is 16 paths. |
Step 6 |
exit Example:
|
Returns to global configuration mode. |
Step 7 |
interface interface-id Example:
|
Enters interface configuration mode, and specifies the Layer 3 interface to configure. |
Step 8 |
ipv6 ospf process-id area area-id [instance instance-id] Example:
|
Enables OSPF for IPv6 on the interface.
|
Step 9 |
end Example:
|
Returns to privileged EXEC mode. |
Step 10 |
Use one of the following:
Example:
or
|
|
Step 11 |
copy running-config startup-config Example:
|
(Optional) Saves your entries in the configuration file. |
Configuring EIGRP for IPv6
Before configuring the switch to run IPv6 EIGRP, enable routing by entering the ip routing global configuration command, enable the forwarding of IPv6 packets by entering the ipv6 unicast-routing global configuration command, and enable IPv6 on any Layer 3 interfaces on which you want to enable IPv6 EIGRP.
To set an explicit router ID, use the show ipv6 eigrp command to see the configured router IDs, and then use the router-id command.
As with EIGRP IPv4, you can use EIGRPv6 to specify your EIGRP IPv6 interfaces and to select a subset of those as passive interfaces. Use the passive-interface command to make an interface passive, and then use the no passive-interface command on selected interfaces to make them active. EIGRP IPv6 does not need to be configured on a passive interface.
For more configuration procedures, see the “Implementing EIGRP for IPv6” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.
Configuring IPv6 Unicast Reverse Path Forwarding
The unicast Reverse Path Forwarding (unicast RPF) feature helps to mitigate problems that are caused by the introduction of malformed or forged (spoofed) IP source addresses into a network by discarding IP packets that lack a verifiable IP source address. For example, a number of common types of denial-of-service (DoS) attacks, including Smurf and Tribal Flood Network (TFN), can take advantage of forged or rapidly changing source IP addresses to allow attackers to thwart efforts to locate or filter the attacks. For Internet service providers (ISPs) that provide public access, Unicast RPF deflects such attacks by forwarding only packets that have source addresses that are valid and consistent with the IP routing table. This action protects the network of the ISP, its customer, and the rest of the Internet.
![]() Note |
|
For detailed IP unicast RPF configuration information, see the Other Security Features chapter in the Cisco IOS Security Configuration Guide, Release 12.4.
Displaying IPv6
For complete syntax and usage information on these commands, see the Cisco IOS command reference publications.
Command |
Purpose |
---|---|
show ipv6 access-list |
Displays a summary of access lists. |
show ipv6 cef |
Displays Cisco Express Forwarding for IPv6. |
show ipv6 interface interface-id |
Displays IPv6 interface status and configuration. |
show ipv6 mtu |
Displays IPv6 MTU per destination cache. |
show ipv6 neighbors |
Displays IPv6 neighbor cache entries. |
show ipv6 ospf |
Displays IPv6 OSPF information. |
show ipv6 prefix-list |
Displays a list of IPv6 prefix lists. |
show ipv6 protocols |
Displays a list of IPv6 routing protocols on the switch. |
show ipv6 rip |
Displays IPv6 RIP routing protocol status. |
show ipv6 rip |
Displays IPv6 RIP routing protocol status. |
show ipv6 route |
Displays IPv6 route table entries. |
show ipv6 routers |
Displays the local IPv6 routers. |
show ipv6 static |
Displays IPv6 static routes. |
show ipv6 traffic |
Displays IPv6 traffic statistics. |
Command |
Purpose |
---|---|
show ipv6 eigrp [as-number] interface |
Displays information about interfaces configured for EIGRP IPv6. |
show ipv6 eigrp [as-number] neighbor |
Displays the neighbors discovered by EIGRP IPv6. |
show ipv6 interface [as-number] traffic |
Displays the number of EIGRP IPv6 packets sent and received. |
show ipv6 eigrp topology [as-number | ipv6-address] [active | all-links | detail-links | pending | summary | zero-successors | Base ] |
Displays EIGRP entries in the IPv6 topology table. |