Implementing DHCP for IPv6

Last Updated: December 19, 2011

This module describes how to configure Dynamic Host Configuration Protocol (DHCP) for IPv6 prefix delegation on your networking devices.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see 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 at the end of this document.

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.

Restrictions for Implementing DHCP for IPv6

  • Cisco IOS Release 12.0S provides IPv6 support on Gigabit Switch Routers (GSRs) and Cisco 10720 Internet routers only.
  • The DHCPv6 Remote-ID for Ethernet Interfaces feature works only for Ethernet interfaces in Cisco IOS Release 12.2(33)SRC.
  • The DHCPv6 implementation in Cisco IOS Release 12.3(4)T, Cisco IOS Release 12.0(32)S, and Cisco IOS 12.2(33)SRC supports only stateless address assignment.

Information About Implementing DHCP for IPv6

DHCPv6 Prefix Delegation

The DHCPv6 Prefix Delegation feature can be used to manage link, subnet, and site addressing changes. DHCPv6 can be used in environments to deliver stateful and stateless information:

  • Stateful--Address assignment is centrally managed and clients must obtain configuration information not available through protocols such as address autoconfiguration and neighbor discovery.
  • Stateless--Stateless configuration parameters do not require a server to maintain any dynamic state for individual clients, such as Domain Name System (DNS) server addresses and domain search list options.

Extensions to DHCPv6 also enable prefix delegation, through which an Internet service provider (ISP) can automate the process of assigning prefixes to a customer for use within the customer's network. Prefix delegation occurs between a provider edge (PE) device and customer premises equipment (CPE), using the DHCPv6 prefix delegation option. Once the ISP has delegated prefixes to a customer, the customer may further subnet and assign prefixes to the links in the customer's network.

Configuring Nodes Without Prefix Delegation

Stateless DHCPv6 allows DHCPv6 to be used for configuring a node with parameters that do not require a server to maintain any dynamic state for the node. The use of stateless DHCP is controlled by router advertisement (RA) messages multicasted by routers. The Cisco IOS DHCPv6 client will invoke stateless DHCPv6 when it receives an appropriate RA. The Cisco IOS DHCPv6 server will respond to a stateless DHCPv6 request with the appropriate configuration parameters, such as the DNS servers and domain search list options.

Client and Server Identification

Each DHCPv6 client and server is identified by a DHCP unique identifier (DUID). The DUID is carried in the client identifier and server identifier options. The DUID is unique across all DHCP clients and servers, and it is stable for any specific client or server. DHCPv6 uses DUIDs based on link-layer addresses for both the client and server identifier. The device uses the MAC address from the lowest-numbered interface to form the DUID. The network interface is assumed to be permanently attached to the device.

When an IPv6 DHCP client requests two prefixes with the same DUID but different IAIDs on two different interfaces, these prefixes are considered to be for two different clients, and interface information is maintained for both.

Rapid Commit

The DHCPv6 client can obtain configuration parameters from a server either through a rapid two-message exchange (solicit, reply) or through a normal four-message exchange (solicit, advertise, request, reply). By default, the four-message exchange is used. When the rapid-commit option is enabled by both client and server, the two-message exchange is used.

DHCPv6 Client Server and Relay Functions

The DHCPv6 client, server, and relay functions are mutually exclusive on an interface. When one of these functions is already enabled and a user tries to configure a different function on the same interface, one of the following messages is displayed: "Interface is in DHCP client mode," "Interface is in DHCP server mode," or "Interface is in DHCP relay mode."

The following sections describe these functions:

Client Function

The DHCPv6 client function can be enabled on individual IPv6-enabled interfaces.

The DHCPv6 client can request and accept those configuration parameters that do not require a server to maintain any dynamic state for individual clients, such as DNS server addresses and domain search list options. The DHCPv6 client will configure the local Cisco IOS stack with the received information.

The DHCPv6 client can also request the delegation of prefixes. The prefixes acquired from a delegating router will be stored in a local IPv6 general prefix pool. The prefixes in the general prefix pool can then be referred to from other applications; for example, the general prefix pools can be used to number router downstream interfaces.

Server Selection

A DHCPv6 client builds a list of potential servers by sending a solicit message and collecting advertise message replies from servers. These messages are ranked based on preference value, and servers may add a preference option to their advertise messages explicitly stating their preference value. If the client needs to acquire prefixes from servers, only servers that have advertised prefixes are considered.

IAPD and IAID

An Identity Association for Prefix Delegation (IAPD) is a collection of prefixes assigned to a requesting router. A requesting router may have more than one IAPD; for example, one for each of its interfaces.

Each IAPD is identified by an identity association identification (IAID). The IAID is chosen by the requesting router and is unique among the IAPD IAIDs on the requesting router. IAIDs are made consistent across reboots by using information from the associated network interface, which is assumed to be permanently attached to the device.

Server Function

The DHCPv6 server function can be enabled on individual IPv6-enabled interfaces.

The DHCPv6 server can provide those configuration parameters that do not require the server to maintain any dynamic state for individual clients, such as DNS server addresses and domain search list options. The DHCPv6 server may be configured to perform prefix delegation.

All the configuration parameters for clients are independently configured into DHCPv6 configuration pools, which are stored in NVRAM. A configuration pool can be associated with a particular DHCPv6 server on an interface when it is started. Prefixes to be delegated to clients may be specified either as a list of preassigned prefixes for a particular client or as IPv6 local prefix pools that are also stored in NVRAM. The list of manually configured prefixes or IPv6 local prefix pools can be referenced and used by DHCPv6 configuration pools.

The DHCPv6 server maintains an automatic binding table in memory to track the assignment of some configuration parameters, such as prefixes between the server and its clients. The automatic bindings can be stored permanently in the database agent, which can be, for example, a remote TFTP server or local NVRAM file system.

Configuration Information Pool

A DHCPv6 configuration information pool is a named entity that includes information about available configuration parameters and policies that control assignment of the parameters to clients from the pool. A pool is configured independently of the DHCPv6 service and is associated with the DHCPv6 service through the command-line interface (CLI).

Each configuration pool can contain the following configuration parameters and operational information:

  • Prefix delegation information, which could include:
    • A prefix pool name and associated preferred and valid lifetimes
    • A list of available prefixes for a particular client and associated preferred and valid lifetimes
  • A list of IPv6 addresses of DNS servers
  • A domain search list, which is a string containing domain names for DNS resolution
DHCP for IPv6 Address Assignment

DHCPv6 enables DHCP servers to pass configuration parameters, such as IPv6 network addresses, to IPv6 clients. The DHCPv6 Individual Address Assignment feature manages nonduplicate 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 the 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 or on multiple interfaces, or the server can automatically find the appropriate pool.

Prefix Assignment

A prefix-delegating router (DHCPv6 server) selects prefixes to be assigned to a requesting router (DHCPv6 client) upon receiving a request from the client. The server can select prefixes for a requesting client using static assignment and dynamic assignment mechanisms. Administrators can manually configure a list of prefixes and associated preferred and valid lifetimes for an IAPD of a specific client that is identified by its DUID.

When the delegating router receives a request from a client, it checks if there is a static binding configured for the IAPD in the client's message. If a static binding is present, the prefixes in the binding are returned to the client. If no such a binding is found, the server attempts to assign prefixes for the client from other sources.

The Cisco IOS DHCPv6 server can assign prefixes dynamically from an IPv6 local prefix pool. When the server receives a prefix request from a client, it attempts to obtain unassigned prefixes from the pool. After the client releases the previously assigned prefixes, the server returns them to the pool for reassignment.

An IPv6 prefix delegating router can also select prefixes for a requesting router based on an external authority such as a RADIUS server using the Framed-IPv6-Prefix attribute. For more information on this feature, see the Implementing ADSL and Deploying Dial Access for IPv6 module.

Automatic Binding

Each DHCPv6 configuration pool has an associated binding table. The binding table contains the records about all the prefixes in the configuration pool that have been explicitly delegated to clients. Each entry in the binding table contains the following information:

  • Client DUID
  • Client IPv6 address
  • A list of IAPDs associated with the client
  • A list of prefixes delegated to each IAPD
  • Preferred and valid lifetimes for each prefix
  • The configuration pool to which this binding table belongs
  • The network interface on which the server that is using the pool is running

A binding table entry is automatically created whenever a prefix is delegated to a client from the configuration pool, and it is updated when the client renews, rebinds, or confirms the prefix delegation. A binding table entry is deleted when the client releases all the prefixes in the binding voluntarily, all prefixes' valid lifetimes have expired, or administrators run the clear ipv6 dhcp binding command.

Binding Database

Each permanent storage to which the binding database is saved is called the database agent. A database agent can be a remote host such as an FTP server or a local file system such as NVRAM.

The automatic bindings are maintained in RAM and can be saved to some permanent storage so that the information about configuration such as prefixes assigned to clients is not lost after a system reload or power down. The bindings are stored as text records for easy maintenance. Each record contains the following information:

  • DHCPv6 pool name from which the configuration was assigned to the client
  • Interface identifier from which the client requests were received
  • The client IPv6 address
  • The client DUID
  • IAID of the IAPD
  • Prefix delegated to the client
  • The prefix length
  • The prefix preferred lifetime in seconds
  • The prefix valid lifetime in seconds
  • The prefix expiration time stamp
  • Optional local prefix pool name from which the prefix was assigned

At the beginning of the file, before the text records, a time stamp records the time when the database is written and a version number, which helps differentiate between newer and older databases. At the end of the file, after the text records, the text string "*end*" is stored to detect file truncation.

The permanent storage to which the binding database is saved is called the database agent. Database agents include FTP and TFTP servers, RCP, flash file system, and NVRAM.

DHCPv6 Server Stateless Autoconfiguration

Hierarchical DHCPv6 for stateless configuration parameters allows a stateless or stateful DHCPv6 client to export configuration parameters (DHCPv6 options) to a local DHCPv6 server pool. The local DHCPv6 server can then provide the imported configuration parameters to other DHCPv6 clients.

The figure below shows a typical broadband deployment.

Figure 1 Broadband Topology


The CPE interface toward the PE can be a stateless or stateful DHCPv6 client. In either case, the ISP-side DHCPv6 server may provide configuration parameters such as DNS server addresses, domain names, and Simple Network Time Protocol (SNTP) servers to the DHCP client on the CPE. These information can be specific to an ISP and may change.

In addition to being a DHCPv6 client (for example, toward the ISP), the CPE may act as a DHCPv6 server to the home network. For example, Neighbor Discovery followed by stateless or stateful DHCPv6 can occur on the link between CPE and the home devices (for example, the home router or PC). In some cases, the information to be provided to the home network is the same information obtained from the ISP-side DHCPv6 server. Because this information can be dynamically changed, it cannot be hard-configured in the CPE's configuration. Therefore, the DHCPv6 component on the CPE allows automatic importing of configuration parameters from the DHCPv6 client to the DHCPv6 server pool.

DHCPv6 provides support of the options for IPv6 on the server described in the following sections:

Information Refresh Server Option

The DHCPv6 information refresh option can specify an upper boundary for the length of time a client should wait before refreshing information retrieved from DHCPv6. This option is used with stateless DHCPv6, because there are no addresses or other entities with lifetimes that can tell the client when to contact the DHCPv6 server to refresh its configuration.

NIS- and NIS+-Related Server Options

Users can configure the network information service (NIS) or NIS plus (NIS+) address or domain name of a DHCPv6 server using NIS- and NIS+-related options, and then import that information to the DHCPv6 client.

SIP Server Options

Session initiation protocol (SIP) server options contain either a list of domain names or IPv6 addresses that can be mapped to one or more SIP outbound proxy servers. One option carries a list of domain names, and the other option carries a list of 128-bit IPv6 addresses.

SIP is an application-layer control protocol that can establish, modify and terminate multimedia sessions or calls. A SIP system has several logical components: user agents, proxy servers, redirect servers, and registrars. User agents may contain SIP clients; proxy servers always contain SIP clients.

SNTP Server Option

The SNTP server option provides a list of one or more IPv6 addresses of SNTP servers available to the client for synchronization. The clients use these SNTP servers to synchronize their system time to that of the standard time servers. The server may list the SNTP servers in decreasing order of preference, but clients must treat the list of SNTP servers as an ordered list.

DHCP Relay Agent

A DHCP relay agent, which may reside on the client's link, is used to relay messages between the client and server. DHCP relay agent operation is transparent to the client. A client locates a DHCP server using a reserved, link-scoped multicast address. Therefore, it is a requirement for direct communication between the client and the server that the client and the server be attached to the same link. However, in some situations in which ease of management, economy, or scalability is a concern, it is desirable to allow a DHCP client to send a message to a DHCP server that is not connected to the same link.

DHCPv6 Relay Agent Notification for Prefix Delegation

DHCPv6 relay agent notification for prefix delegation allows the router working as a DHCPv6 relay agent to find prefix delegation options by reviewing the contents of a DHCPv6 RELAY-REPLY packet that is being relayed by the relay agent to the client. When a prefix delegation option is found by the relay agent, the relay agent extracts the information about the prefix being delegated and inserts an IPv6 static route matching the prefix delegation information onto the relay agent. Future packets destined to that prefix via relay will be forwarded based on the information contained in the prefix delegation. The IPv6 static route is then left in the routing table until the prefix delegation lease time expires or the relay agent receives a release packet from the client releasing the prefix delegation.

No user configuration is required for this feature. Static route management is done automatically by the relay agent.

The IPv6 routes are added when the relay agent relays a RELAY-REPLY packet, and the IPv6 routes are deleted when the prefix delegation lease time expires or the relay agent receives a release message. An IPv6 static route in the routing table of the relay agent can be updated when the prefix delegation lease time is extended.

This feature leaves a static IPv6 route on the routing table of the relay agent. This registered IPv6 address allows unicast reverse packet forwarding (uRPF) to work by allowing the router doing the reverse lookup to confirm that the IPv6 address on the relay agent is not malformed or spoofed. The static route left in the routing table of the relay agent can be redistributed to other routing protocols to advertise the subnets to other nodes. The static routes will be removed when an DHCP_DECLINE message is sent by the client.

DHCPv6 Bulk-Lease Query

DHCPv6 supports bulk-lease query that allows a client to request information about DHCPv6 bindings. This functionality adds new query types and allows the bulk transfer of DHCPv6 binding data through TCP.

Bulk-lease query is enabled by default if the DHCPv6 relay agent is enabled. Bulk-lease query is triggered at the relay agent startup to retrieve binding information lost because of a reload. If a DHCPv6 relay destination is configured on an interface, bulk-lease query is performed by the IPv6 address of the interface on which DHCPv6 relay is enabled. Bulk-lease query is a separate process from the relay agent process.

DHCPv6 Relay Chaining

DHCPv6 messages can be relayed through multiple relay agents. This concept is called Relay Chaining. Such a configuration can be supported only when each relay agent adds certain information to DHCPv6 messages before relaying them. The additional information helps in relaying the DHCPv6 reply back to the DHCPv6 client through the same path.

The delegated IPv6 prefix must be routable in order to be useful. The actual DHCPv6 PD client may not be permitted to inject routes into the delegating network. In service-provider (SP) networks, for example, an edge router typically acts as a DHCPv6 relay agent, and this edge router often has the responsibility to maintain routes within the service-provider network for clients' PD bindings. In the event that DHCPv6 requests and responses are relayed through a chain of DHCPv6 relays, there may be a need to introduce appropriate routes (particularly with DHCPv6-PD) in the FIB so that routing is handled transparently.

DHCPv6 Relay Source Configuration

The DHCPv6 server sends its replies to the source address of relayed messages. Normally, a DHCPv6 relay uses the address of the server-facing interface used to send messages as the source. However, in some networks, it may be desirable to configure a more stable address (such as a loopback interface) and have the relay use that interface as the source address of relayed messages. The DHCPv6 Relay Source Configuration feature provides this capability.

The figure below shows a simple network with a single client, relay, and server. The relay and server communicate over 2001:DB8:1::/64, and the relay has a client-facing interface on 2001:DB8:2::/64. The relay also has a loopback interface configured with address 2001:DB8:3:1/64.

Figure 2 DHCPv6 Relay Source Configuration--Simple Network


When the relay receives a request from the client, the relay includes an address from the client-facing interface (Ethernet 1/0) in the link-address field of a relay-forward message. This address is used by the server to select an address pool. The relay then sends the relay-forward message toward the server. By default, the address of the server-facing (Ethernet 0/0) interface is used as the IPv6 source, and the server will send any reply to that address.

If the relay source interface is explicitly configured, the relay will use that interface's primary IPv6 address as the IPv6 source for messages it forwards. For example, configuring Loopback 0 as the source would cause the relay to use 2001:DB8:3:1/64 as the IPv6 source address for messages relayed toward the server.

DHCPv6 Relay SSO and ISSU

In specific Cisco networking devices that support dual RPs, stateful switchover (SSO) takes advantage of RP redundancy to increase network availability. The feature establishes one of the RPs as the active processor while the other RP is designated as the standby processor, and then synchronizing critical state information between them. Following an initial synchronization between the two processors, SSO dynamically maintains RP state information between them.

The Cisco IOS In Service Software Upgrade (ISSU) process allows Cisco IOS software to be updated or otherwise modified while packet forwarding continues. In most networks, planned software upgrades are a significant cause of downtime. ISSU allows Cisco IOS software to be modified while packet forwarding continues, which increases network availability and reduces downtime caused by planned software upgrades.

SSO and ISSU use redundant hardware, with the active and standby RP each running an instance of the DHCP relay agent. Both instances exchange run-time state data.

For further information about SSO and ISSU, see the "Stateful Switchover" and "Cisco IOS In Service Software Upgrade Process" modules in the Cisco IOS High Availability Configuration Guide.

DHCPv6 Relay Options: Remote-ID for Ethernet Interfaces

This feature adds the remote identification (remote-ID) option to relayed (RELAY-FORWARD) DHCPv6 packets.

The remote-ID option provides information to the DHCPv6 server, including port information, the system's DUID, and the VLAN ID. Collectively, this information can be used to uniquely identify both the relay and the port on the relay through which the client's packet arrived. The DHCPv6 server uses this information to select parameters specific to a particular user, host, or subscriber modem. This feature works only for Ethernet interfaces at this time.

This feature introduces no user configuration. Because the addition of the remote-ID option to the RELAY-FORWARD packet occurs automatically, no user configuration is necessary.

The DHCPv6 server does not need to echo the remote-ID option in the RELAY-REPLY packet. Internet Assigned Numbers Authority (IANA) has assigned the DHCPv6 option code 37 for the relay agent remote-ID option.

If the remote-ID option is included in the RELAY-REPLY packet, the option is stripped out of the packet before the packet is relayed to the client.

DHCPv6 Relay Options: Reload Persistent Interface-ID

This feature makes the interface-ID option, which is used by relay agents to decide which interface should be used when forwarding a RELAY-REPLY packet, persistent. A persistent interface-ID option will not change if the router acting as a relay agent goes offline (such as during a reload or a power outage). When the router acting as a relay agent returns online, it is possible that changes to the internal interface index of the relay agent may have occurred in certain scenarios (such as cases where the relay agent reboots and has a change in the number of interfaces in the interface index, or the relay agents boots up and has more virtual interfaces than it did before the reboot). This feature prevents this scenario from causing any problems.

This feature changes the DHCPv6 interface-ID option to be expressed as simply the short form of the interface name. This syntax helps avoid potential problems that could arise due to physical or logical interfaces changing on the relay agent after a reload.

DHCPv6 Server and Relay - MPLS VPN Support

To facilitate managed central services in a Multiprotocol Label Switching (MPLS)-based network, DHCPv6 must be made MPLS-aware so a single resource can be used to serve multiple virtual private networks (VPNs) instead of dedicating a resource to a single VPN.

The DHCPv6 server implementation of MPLS VPN support allows a per-pool configuration so DHCPv6 pools can be associated with a VPN routing and forwarding (VRF) instance. The DHCPv6 server differentiates clients from various VRFs and assigns an IPv6 prefix accordingly from the respective VRF pools. Meanwhile, the DHCPv6 bindings store clients' VRF information.

The DHCPv6 relay implementation allows the configuration of the destination VRF instance to which the relay messages will be forwarded. The relay adds the client's VPN information while forwarding the client's DHCPv6 requests toward the server, and the relay then processes the client's VPN information in reply packets from server.

The relay adds IPv6 static routes for delegated prefixes in corresponding clients' VRF, and the relay's high availability (HA) functionality synchronizes the VRF information while synchronizing static routes created by the relay process.

The DHCPv6 relay and server VRF-aware features are disabled by default for backward compatibility.

How to Implement DHCP for IPv6

Configuring the DHCPv6 Server Function

The tasks in the following sections explain how to configure DHCPv6 server function:

Configuring the DHCPv6 Configuration Pool

Perform this task to create and configure the DHCPv6 configuration pool and associate the pool with a server on an interface.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ipv6 dhcp pool poolname

4.    domain-name domain

5.    dns-server ipv6-address

6.    prefix-delegation ipv6-prefix / prefix-length client-duid [iaid iaid] [lifetime]

7.    prefix-delegation pool poolname [lifetime valid-lifetime preferred-lifetime]

8.    exit

9.    interface type number

10.    ipv6 dhcp server poolname [rapid-commit] [preference value] [allow-hint


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 dhcp pool poolname


Example:

Router(config)# ipv6 dhcp pool pool1

 

Configures a DHCPv6 configuration information pool and enters DHCPv6 pool configuration mode.

 
Step 4
domain-name domain


Example:

Router(config-dhcp)# domain-name example.com

 

Configures a domain name for a DHCPv6 client.

 
Step 5
dns-server ipv6-address


Example:

Router(config-dhcp)# dns-server 2001:DB8:3000:3000::42

 

Specifies the DNS IPv6 servers available to a DHCPv6 client.

 
Step 6
prefix-delegation ipv6-prefix / prefix-length client-duid [iaid iaid] [lifetime]


Example:

Router(config-dhcp)# prefix-delegation 2001:DB8:1263::/48 0005000400F1A4D070D03

 

Specifies a manually configured numeric prefix to be delegated to a specified client's IAPD.

 
Step 7
prefix-delegation pool poolname [lifetime valid-lifetime preferred-lifetime]


Example:

Router(config-dhcp)# prefix-delegation pool pool1 lifetime 1800 60

 

Specifies a named IPv6 local prefix pool from which prefixes are delegated to DHCPv6 clients.

 
Step 8
exit


Example:

Router(config-dhcp)# exit

 

Exits DHCPv6 pool configuration mode configuration mode, and returns the router to global configuration mode.

 
Step 9
interface type number


Example:

Router(config)# interface serial 3

 

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

 
Step 10
ipv6 dhcp server poolname [rapid-commit] [preference value] [allow-hint


Example:

Router(config-if)# ipv6 dhcp server pool1

 

Enables DHCPv6 on an interface.

 

Configuring a Binding Database Agent for the Server Function

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ipv6 dhcp database agent [write-delay seconds] [timeout seconds


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 dhcp database agent [write-delay seconds] [timeout seconds


Example:

Router(config)# ipv6 dhcp database tftp://10.0.0.1/dhcp-binding

 

Specifies DHCPv6 binding database agent parameters.

 

Configuring the DHCPv6 Client Function

General prefixes can be defined dynamically from a prefix received by a DHCPv6 prefix delegation client. The delegated prefix is stored in a general prefix.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    interface type number

4.    ipv6 dhcp client pd {prefix-name | hint ipv6-prefix} [rapid-commit


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 fastethernet 0/0/0

 

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

 
Step 4
ipv6 dhcp client pd {prefix-name | hint ipv6-prefix} [rapid-commit


Example:

Router(config-if)# ipv6 dhcp client pd dhcp-prefix

 

Enables the DHCPv6 client process and enables a request for prefix delegation through a specified interface.

 

Configuring the DHCPv6 Relay Agent

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    interface type number

4.    ipv6 dhcp relay destination ipv6-address [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
interface type number


Example:

Router(config)# interface ethernet 4/2

 

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

 
Step 4
ipv6 dhcp relay destination ipv6-address [interface-type interface-number


Example:

Router(config-if) ipv6 dhcp relay destination FE80::250:A2FF:FEBF:A056 ethernet 4/3

 

Specifies a destination address to which client packets are forwarded and enables DHCPv6 relay service on the interface.

 

Configuring Route Addition for Relay/Server

To enable route addition by Dynamic Host Configuration Protocol for IPv6 (DHCPv6) relay and server for the delegated prefix, use the ipv6 dhcp iapd-route-add command in global configuration mode.

To add routes for individually assigned IPv6 addresses on relay/server, use the ipv6 dhcp iana-route-add command in global configuration mode

Configuring a DHCPv6 Relay Source

Perform the following tasks to configure a DHCPv6 relay source:

Restrictions for Configuring a DHCPv6 Relay Source

  • If the configured interface is shut down, or if all of its IPv6 addresses are removed, the relay will revert to its standard behavior.
  • The command line interface (CLI) will report an error if the user attempts to specify an interface that has no IPv6 addresses configured.
  • The interface configuration takes precedence over the global configuration if both have been configured.

Configuring a DHCPv6 Relay Source on an Interface

Perform this task to configure an interface to use as the source when relaying messages.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    interface type number

4.    ipv6 dhcp relay source-interface 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
interface type number


Example:

Router(config)# interface loopback 0

 

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

 
Step 4
ipv6 dhcp relay source-interface interface-type interface-number


Example:

Router(config-if)# ipv6 dhcp relay source-interface loopback 0

 

Configures an interface to use as the source when relaying messages received on this interface.

 

Configuring a DHCPv6 Relay Source Globally

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ipv6 dhcp-relay source-interface 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 dhcp-relay source-interface interface-type interface-number


Example:

Router(config)# ipv6 dhcp-relay source-interface loopback 0

 

Configures an interface to use as the source when relaying messages.

 

Configuring DHCPv6 Bulk-Lease Query Parameters

The DHCPv6 Bulk-Lease Query feature is enabled automatically when the DHCPv6 relay agent is enabled.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ipv6 dhcp-relay bulk-lease {data-timeout seconds| retry number} [disable]


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 dhcp-relay bulk-lease {data-timeout seconds| retry number} [disable]


Example:

Router(config)# ipv6 dhcp-relay bulk-lease data-timeout 60

 

Configures bulk-lease query parameters.

 

Configuring DHCP for IPv6 Address Assignment

Perform the following tasks describe configure DHCPv6 address assignment:

Prerequisites for Configuring DHCPv6 Address Assignment

By default, no DHCPv6 features are configured on the router.

When configuring DHCPv6 address assignment, remember that the specified interface must be one of these Layer 3 interfaces:

  • Switch Virtual Interface (SVI): a VLAN interface created by using the interface vlan vlan-id command.
  • EtherChannel port channel in Layer 3 mode: a port-channel logical interface created by using the interface port-channel port-channel-number command.

Enabling the DHCPv6 Server Function on an Interface

Perform this task to enable the DHCPv6 server function on an interface. Note that to delete a DHCPv6 pool, you must use the no ipv6 dhcp pool poolname global configuration command. Use the no form of the DHCP pool configuration mode commands to change the DHCPv6 pool characteristics. To disable the DHCPv6 server function on an interface, use the no ipv6 dhcp server interface configuration command.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ipv6 dhcp pool poolname

4.    address prefix ipv6-prefix [lifetime {valid-lifetime preferred-lifetime | infinite}]

5.    link-address ipv6-prefix

6.    vendor-specific vendor-id

7.    suboption number {address ipv6-address| ascii ascii-string | hex hex-string}

8.    exit

9.    exit

10.    interface type number

11.    ipv6 dhcp server [poolname| automatic] [rapid-commit] [preference value] [allow-hint]

12.    end

13.   Do one of the following:

  • show ipv6 dhcp pool
  • show ipv6 dhcp interface

14.    copy running-config startup-config


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(config)# configure terminal

 

Enters global configuration mode.

 
Step 3
ipv6 dhcp pool poolname


Example:

Router(config)# ipv6 dhcp pool engineering

 

Enters DHCP pool configuration mode, and defines the name of the IPv6 DHCP pool.

 
Step 4
address prefix ipv6-prefix [lifetime {valid-lifetime preferred-lifetime | infinite}]


Example:

Router(config-dhcpv6)# address prefix 2001:1000::0/64 lifetime infinite

 

(Optional) Specifies an address prefix for address assignment.

  • This address must be in hexadecimal, using 16-bit values between colons.
  • lifetime valid-lifetime preferred-lifetime --Specifies a time interval (in seconds) that an IPv6 address prefix remains in the valid state.
 
Step 5
link-address ipv6-prefix


Example:

Router(config-dhcpv6)# link-address 2001:1001::0/64

 

(Optional) Specifies a link-address IPv6 prefix.

  • When an address on the incoming interface or a link address in the packet matches the specified IPv6 prefix, the server uses the configuration information pool.
 
Step 6
vendor-specific vendor-id


Example:

Router(config-dhcpv6)# vendor-specific 9

 

(Optional) Enters vendor-specific configuration mode with the vendor-specific identification number.

 
Step 7
suboption number {address ipv6-address| ascii ascii-string | hex hex-string}


Example:

Router(config-dhcpv6-vs)# suboption 1 address 1000:235D::1

 

(Optional) Enters a vendor-specific suboption number.

 
Step 8
exit


Example:

Router(config-dhcpv6-vs)# exit

 

Returns to DHCP pool configuration mode.

 
Step 9
exit


Example:

Router(config-dhcpv6)# exit

 

Returns to global configuration mode.

 
Step 10
interface type number


Example:

Router(config)# interface fastethernet 0/0

 

Enters interface configuration mode, and specifies the interface to configure.

 
Step 11
ipv6 dhcp server [poolname| automatic] [rapid-commit] [preference value] [allow-hint]


Example:

Router(config-if)# ipv6 address dhcp server rapid-commit

 

Enables DHCPv6 server function on an interface.

 
Step 12
end


Example:

Router(config-if)# end

 

Returns to privileged EXEC mode.

 
Step 13
Do one of the following:
  • show ipv6 dhcp pool
  • show ipv6 dhcp interface


Example:

Router# show ipv6 dhcp pool



Example:



Example:

Router# show ipv6 dhcp interface

 

Verifies DHCPv6 pool configuration or verifies that the DHCPv6 server function is enabled on an interface.

 
Step 14
copy running-config startup-config


Example:

Router# copy running-config startup-config

 

(Optional) Saves your entries in the configuration file.

 

Enabling the DHCPv6 Client Function on an Interface

Perform this task to enable the DHCPv6 client function on an interface. To disable the DHCPv6 client function, use the no ipv6 address dhcp interface configuration command. To remove the DHCPv6 client request, use the no ipv6 address dhcp client request vendorinterface configuration command.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    interface type number

4.    ipv6 address dhcp [rapid-commit]

5.    ipv6 address dhcp client request vendor

6.    end

7.    show ipv6 dhcp interface


DETAILED STEPS
  Command or Action Purpose
Step 1
enable


Example:

Router> enable

 

Enables privileged EXEC mode.

  • Enter password if prompted.
 
Step 2
configure terminal


Example:

Router# configure terminal

 

Enters global configuration mode.

 
Step 3
interface type number


Example:

Router(config)# interface fastethernet 0/0

 

Enters interface configuration mode, and specifies the interface to configure.

 
Step 4
ipv6 address dhcp [rapid-commit]


Example:

Router(config-if)# ipv6 address dhcp rapid-commit

 

Enables the interface to acquire an IPv6 address from the DHCPv6 server.

 
Step 5
ipv6 address dhcp client request vendor


Example:

Router(config-if)# ipv6 dhcp client request vendor-specific

 

(Optional) Enables the interface to request the vendor-specific option.

 
Step 6
end


Example:

Router(config-if)# end

 

Returns to privileged EXEC mode.

 
Step 7
show ipv6 dhcp interface


Example:

Router# show ipv6 dhcp interface

 

Verifies that the DHCPv6 client is enabled on an interface.

 

Configuring the Stateless DHCPv6 Function

The server maintains no state related to clients; for example, no prefix pools and records of allocation are maintained. Therefore, this function is "stateless" DHCPv6.

Configuring the Stateless DHCPv6 Server

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ipv6 dhcp pool poolname

4.    dns-server ipv6-address

5.    domain-name domain

6.    exit

7.    interface type number

8.    ipv6 dhcp server poolname [rapid-commit] [preference value] [allow-hint]

9.    ipv6 nd other-config-flag


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 dhcp pool poolname


Example:

Router(config)# ipv6 dhcp pool dhcp-pool

 

Configures a DHCPv6 configuration information pool and enters DHCPv6 pool configuration mode.

 
Step 4
dns-server ipv6-address


Example:

Router(config-dhcp) dns-server 2001:DB8:3000:3000::42

 

Specifies the DNS IPv6 servers available to a DHCPv6 client.

 
Step 5
domain-name domain


Example:

Router(config-dhcp)# domain-name domain1.com

 

Configures a domain name for a DHCPv6 client.

 
Step 6
exit


Example:

Router(config-dhcp)# exit

 

Exits DHCPv6 pool configuration mode configuration mode, and returns the router to global configuration mode.

 
Step 7
interface type number


Example:

Router(config)# interface serial 3

 

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

 
Step 8
ipv6 dhcp server poolname [rapid-commit] [preference value] [allow-hint]


Example:

Router(config-if)# ipv6 dhcp server dhcp-pool

 

Enables DHCPv6 on an interface.

 
Step 9
ipv6 nd other-config-flag


Example:

Router(config-if)# ipv6 nd other-config-flag

 

Sets the "other stateful configuration" flag in IPv6 RAs.

 

Configuring the Stateless DHCPv6 Client

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    interface type number

4.    ipv6 address autoconfig [default]


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
ipv6 address autoconfig [default]


Example:

Router(config-if)# ipv6 address autoconfig

 

Enables automatic configuration of IPv6 addresses using stateless autoconfiguration on an interface and enables IPv6 processing on the interface.

 

Enabling Processing of Packets with Source Routing Header Options

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ipv6 source-route


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 source-route


Example:

Router(config)# ipv6 source-route

 

Enables processing of the IPv6 type 0 routing header.

 

Configuring the DHCPv6 Server Options

Configuring the Information Refresh Server Option

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ipv6 dhcp pool poolname

4.    information refresh {days [hours minutes] | infinity}


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 dhcp pool poolname


Example:

Router(config)# ipv6 dhcp pool pool1

 

Configures a DHCPv6 configuration information pool and enters DHCPv6 pool configuration mode.

 
Step 4
information refresh {days [hours minutes] | infinity}


Example:

Router(config-dhcp)# information refresh 1 1 1

 

Specifies the information refresh time to be sent to the client.

 

Importing the Information Refresh Server Option

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ipv6 dhcp pool poolname

4.    import information refresh


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 dhcp pool poolname


Example:

Router(config)# ipv6 dhcp pool pool1

 

Configures a DHCPv6 configuration information pool and enters DHCPv6 pool configuration mode.

 
Step 4
import information refresh


Example:

Router(config-dhcp)# import information refresh

 

Imports the information refresh time option to a DHCPv6 client.

 

Configuring NIS- and NISP-Related Server Options

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ipv6 dhcp pool poolname

4.    nis address ipv6-address

5.    nis domain-name domain-name

6.    nisp address ipv6-address

7.    nisp domain-name domain-name


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 dhcp pool poolname


Example:

Router(config)# ipv6 dhcp pool pool1

 

Configures a DHCPv6 configuration information pool and enters DHCPv6 pool configuration mode.

 
Step 4
nis address ipv6-address


Example:

Router(config-dhcp)# nis address 2001:DB8:1000:1000::30

 

Specifies the NIS address of an IPv6 server to be sent to the client.

 
Step 5
nis domain-name domain-name


Example:

Router(config-dhcp)# nis domain-name domain1

 

Enables a server to convey a client's NIS domain name information to the client.

 
Step 6
nisp address ipv6-address


Example:

Router(config-dhcp)# nisp address 2001:DB8:3000:3000::42

 

Specifies the NIS+ address of an IPv6 server to be sent to the DHCPv6 client.

 
Step 7
nisp domain-name domain-name


Example:

Router(config-dhcp)# nisp domain-name domain2

 

Enables a server to convey a client's NIS+ domain name information to the DHCPv6 client.

 

Importing NIS- and NIS+-Related Server Options

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ipv6 dhcp pool poolname

4.    import nis address

5.    import nis domain-name

6.    import nisp address

7.    import nisp domain-name


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 dhcp pool poolname


Example:

Router(config)# ipv6 dhcp pool pool1

 

Configures a DHCPv6 configuration information pool and enters DHCPv6 pool configuration mode.

 
Step 4
import nis address


Example:

Router(config-dhcp)# import nis address

 

Imports the NIS servers option to a DHCPv6 client.

 
Step 5
import nis domain-name


Example:

Router(config-dhcp)# import nis domain-name

 

Imports the NIS domain name option to a DHCPv6 client.

 
Step 6
import nisp address


Example:

Router(config-dhcp)# import nisp address

 

Imports the NISP address option to a DHCPv6 client.

 
Step 7
import nisp domain-name


Example:

Router(config-dhcp)# import nisp domain-name

 

Imports the NISP domain name option to a DHCPv6 client.

 

Importing SIP Server Options

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ipv6 dhcp pool poolname

4.    import sip address

5.    import sip domain-name


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 dhcp pool poolname


Example:

Router(config)# ipv6 dhcp pool pool1

 

Configures a DHCPv6 configuration information pool and enters DHCPv6 pool configuration mode.

 
Step 4
import sip address


Example:

Router(config-dhcp)# import sip address

 

Imports the SIP server IPv6 address list option to the outbound SIP proxy server.

 
Step 5
import sip domain-name


Example:

Router(config-dhcp)# import sip domain-name

 

Imports a SIP server domain-name list option to the outbound SIP proxy server.

 

Configuring the SNTP Server Option

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ipv6 dhcp pool poolname

4.    sntp address ipv6-address


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 dhcp pool poolname


Example:

Router(config)# ipv6 dhcp pool pool1

 

Configures a DHCPv6 configuration information pool and enters DHCPv6 pool configuration mode.

 
Step 4
sntp address ipv6-address


Example:

Router(config-dhcp)# sntp address 2001:DB8:2000:2000::33

 

Specifies the SNTP server list to be sent to the client.

 

Importing the SNTP Server Option

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ipv6 dhcp pool poolname

4.    import sntp address ipv6-address


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 dhcp pool poolname


Example:

Router(config)# ipv6 dhcp pool pool1

 

Configures a DHCPv6 configuration information pool and enters DHCPv6 pool configuration mode.

 
Step 4
import sntp address ipv6-address


Example:

Router(config-dhcp)# import sntp address 2001:DB8:2000:2000::33

 

Imports the SNTP server option to a DHCPv6 client.

 

Importing Stateless DHCPv6 Server Options

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ipv6 dhcp pool poolname

4.    import dns-server

5.    import domain-name


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 dhcp pool poolname


Example:

Router(config)# ipv6 dhcp pool pool1

 

Configures a DHCPv6 configuration information pool and enters DHCPv6 pool configuration mode.

 
Step 4
import dns-server


Example:

Router(config-dhcp)# import dns-server

 

Imports the DNS recursive name server option to a DHCPv6 client.

 
Step 5
import domain-name


Example:

Router(config-dhcp)# import domain-name

 

Imports the domain search list option to a DHCPv6 client.

 

Defining a General Prefix with the DHCPv6 Prefix Delegation Client Function

Perform this task to configure the DHCPv6 client function on an interface and enable prefix delegation on an interface. The delegated prefix is stored in a general prefix.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    interface type number

4.    ipv6 dhcp client pd {prefix-name | hint ipv6-prefix} [rapid-commit


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 ethernet 0/0

 

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

 
Step 4
ipv6 dhcp client pd {prefix-name | hint ipv6-prefix} [rapid-commit


Example:

Router(config-if)# ipv6 dhcp client pd dhcp-prefix

 

Enables the DHCPv6 client process and enables a request for prefix delegation through a specified interface.

  • The delegated prefix is stored in the general prefix prefix-name argument.
 

Configuring a VRF-Aware Relay and Server for MPLS VPN Support

Configuring a VRF-Aware Relay

Note that you do not have to configure this feature on specified interfaces; if you want the feature to be enabled globally on the router only, perform steps 1, 2, and 3.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ipv6 dhcp-relay option vpn

4.    interface type number

5.    ipv6 dhcp relay option vpn

6.    ipv6 dhcp relay destination ipv6-address [interface-type interface-number | vrf vrf-name| global]


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 dhcp-relay option vpn


Example:

Router(config)# ipv6 dhcp-relay option vpn

 

Enables the DHCP for IPv6 relay VRF-aware feature globally.

 
Step 4
interface type number


Example:

Router(config)# interface ethernet 0/0

 

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

 
Step 5
ipv6 dhcp relay option vpn


Example:

Router(config-if)# ipv6 dhcp relay option vpn

 

Enables the DHCP for IPv6 relay VRF-aware feature on the specified interface. Enabling this command supersedes configuration using the ipv6 dhcp-relay option vpncommand.

 
Step 6
ipv6 dhcp relay destination ipv6-address [interface-type interface-number | vrf vrf-name| global]


Example:

Router(config-if)# ipv6 dhcp relay destination FE80::250:A2FF:FEBF:A056 ethernet 0/0

 

Specifies a destination address to which client messages are forwarded.

 

Configuring a VRF-Aware Server

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    interface type number

4.    ipv6 dhcp server vrf enable


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 ethernet 0/0

 

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

 
Step 4
ipv6 dhcp server vrf enable


Example:

Router(config-if)# ipv6 dhcp server vrf enable

 

Enables the DHCPv6 server VRF-aware feature on an interface.

 

Deleting Automatic Client Bindings from the DHCPv6 Binding Table

SUMMARY STEPS

1.    enable

2.    clear ipv6 dhcp binding [ipv6-address] [vrf vrf-name]


DETAILED STEPS
  Command or Action Purpose
Step 1
enable


Example:

Router> enable

 

Enables privileged EXEC mode.

  • Enter your password if prompted.
 
Step 2
clear ipv6 dhcp binding [ipv6-address] [vrf vrf-name]


Example:

Router# clear ipv6 dhcp binding

 

Deletes automatic client bindings from the DHCPv6 binding table.

 

Troubleshooting DHCPv6

SUMMARY STEPS

1.    enable

2.    debug ipv6 dhcp [detail

3.    debug ipv6 dhcp database

4.    debug ipv6 dhcp relay


DETAILED STEPS
  Command or Action Purpose
Step 1
enable


Example:

Router> enable

 

Enables privileged EXEC mode.

  • Enter your password if prompted.
 
Step 2
debug ipv6 dhcp [detail


Example:

Router# debug ipv6 dhcp

 

Enables debugging for DHCPv6.

 
Step 3
debug ipv6 dhcp database


Example:

Router# debug ipv6 dhcp database

 

Enables debugging for the DHCPv6 binding database.

 
Step 4
debug ipv6 dhcp relay


Example:

Router# debug ipv6 dhcp relay

 

Enables DHCPv6 relay agent debugging.

 

Verifying DHCPv6 Configuration and Operation

SUMMARY STEPS

1.    enable

2.    show ipv6 dhcp

3.    show ipv6 dhcp binding [ipv6-address

4.    show ipv6 dhcp database [agent-URL

5.    show ipv6 dhcp interface [type number]

6.    show ipv6 dhcp pool [poolname

7.    show running-config


DETAILED STEPS
  Command or Action Purpose
Step 1
enable


Example:

Router# enable

 

Enables privileged EXEC mode.

  • Enter your password if prompted.
 
Step 2
show ipv6 dhcp


Example:

Router# show ipv6 dhcp

 

Displays the DUID on a specified device.

 
Step 3
show ipv6 dhcp binding [ipv6-address


Example:

Router# show ipv6 dhcp binding

 

Displays automatic client bindings from the DHCPv6 database.

 
Step 4
show ipv6 dhcp database [agent-URL


Example:

Router# show ipv6 dhcp database

 

Displays the DHCPv6 binding database agent information.

 
Step 5
show ipv6 dhcp interface [type number]


Example:

Router# show ipv6 dhcp interface

 

Displays DHCPv6 interface information.

 
Step 6
show ipv6 dhcp pool [poolname


Example:

Router# show ipv6 dhcp pool

 

Displays DHCPv6 configuration pool information.

 
Step 7
show running-config


Example:

Router# show running-config

 

Displays the current configuration running on the router.

 

Examples

Sample Output from the show ipv6 dhcp Command

The following example from the show ipv6 dhcpcommand shows the DUID of the device:

Router# show ipv6 dhcp 
This device's DHCPv6 unique identifier(DUID): 000300010002FCA5DC1C
Sample Output from the show ipv6 dhcp binding Command

In the following example, the show ipv6 dhcp binding command shows information about two clients, including their DUIDs, IAPDs, prefixes, and preferred and valid lifetimes:

Router# show ipv6 dhcp binding
Client: FE80::202:FCFF:FEA5:DC39 (Ethernet2/1)
  DUID: 000300010002FCA5DC1C
  IA PD: IA ID 0x00040001, T1 0, T2 0
    Prefix: 3FFE:C00:C18:11::/68
            preferred lifetime 180, valid lifetime 12345
            expires at Nov 08 2002 02:24 PM (12320 seconds)
Client: FE80::202:FCFF:FEA5:C039 (Ethernet2/1)
  DUID: 000300010002FCA5C01C
  IA PD: IA ID 0x00040001, T1 0, T2 0
    Prefix: 3FFE:C00:C18:1::/72
            preferred lifetime 240, valid lifetime 54321
            expires at Nov 09 2002 02:02 AM (54246 seconds)
    Prefix: 3FFE:C00:C18:2::/72
            preferred lifetime 300, valid lifetime 54333
            expires at Nov 09 2002 02:03 AM (54258 seconds)
    Prefix: 3FFE:C00:C18:3::/72
            preferred lifetime 280, valid lifetime 51111
Sample Output from the show ipv6 dhcp database Command

In the following example, the show ipv6 dhcp database command provides information on the binding database agents TFTP, NVRAM, and flash:

Router# show ipv6 dhcp database 
Database agent tftp://172.19.216.133/db.tftp:
  write delay: 69 seconds, transfer timeout: 300 seconds
  last written at Jan 09 2003 01:54 PM,
     write timer expires in 56 seconds
  last read at Jan 06 2003 05:41 PM
  successful read times 1
  failed read times 0
  successful write times 3172
  failed write times 2
Database agent nvram:/dhcpv6-binding:
  write delay: 60 seconds, transfer timeout: 300 seconds
  last written at Jan 09 2003 01:54 PM,
     write timer expires in 37 seconds
  last read at never
  successful read times 0
  failed read times 0
  successful write times 3325
  failed write times 0
Database agent flash:/dhcpv6-db:
  write delay: 82 seconds, transfer timeout: 3 seconds
  last written at Jan 09 2003 01:54 PM,
    write timer expires in 50 seconds
  last read at never
  successful read times 0
  failed read times 0
  successful write times 2220
  failed write times 614
Sample Output from the show ipv6 dhcp interface Command

The following is sample output from the show ipv6 dhcp interfacecommand. In the first example, the command is used on a router that has an interface acting as a DHCPv6 server. In the second example, the command is used on a router that has an interface acting as a DHCPv6 client:

Router1# show ipv6 dhcp interface
Ethernet2/1 is in server mode
  Using pool: svr-p1
  Preference value: 20
  Rapid-Commit is disabled
Router2# show ipv6 dhcp interface
Ethernet2/1 is in client mode
  State is OPEN (1)
  List of known servers:
    Address: FE80::202:FCFF:FEA1:7439, DUID 000300010002FCA17400
    Preference: 20
      IA PD: IA ID 0x00040001, T1 120, T2 192
        Prefix: 3FFE:C00:C18:1::/72
                preferred lifetime 240, valid lifetime 54321
                expires at Nov 08 2002 09:10 AM (54319 seconds)
        Prefix: 3FFE:C00:C18:2::/72
                preferred lifetime 300, valid lifetime 54333
                expires at Nov 08 2002 09:11 AM (54331 seconds)
        Prefix: 3FFE:C00:C18:3::/72
                preferred lifetime 280, valid lifetime 51111
                expires at Nov 08 2002 08:17 AM (51109 seconds)
      DNS server: 2001:DB8:1001::1
      DNS server: 2001:DB8:1001::2
      Domain name: example1.net
      Domain name: example2.net 
      Domain name: example3.net
    Prefix name is cli-p1
    Rapid-Commit is enabled
Sample Output from the show ipv6 dhcp pool Command

In the following example, the show ipv6 dhcp pool command provides information on the configuration pool named svr-p1, including the static bindings, prefix information, the DNS server, and the domain names found in the svr-p1 pool:

Router# show ipv6 dhcp pool
 
DHCPv6 pool: svr-p1
  Static bindings:
    Binding for client 000300010002FCA5C01C
      IA PD: IA ID 00040002, 
        Prefix: 3FFE:C00:C18:3::/72
                preferred lifetime 604800, valid lifetime 2592000
      IA PD: IA ID not specified; being used by 00040001
        Prefix: 3FFE:C00:C18:1::/72
                preferred lifetime 240, valid lifetime 54321
        Prefix: 3FFE:C00:C18:2::/72
                preferred lifetime 300, valid lifetime 54333
        Prefix: 3FFE:C00:C18:3::/72
                preferred lifetime 280, valid lifetime 51111
  Prefix from pool: local-p1, Valid lifetime 12345, Preferred lifetime 180
  DNS server: 2001:DB8:1001::1
  DNS server: 2001:DB8:1001::2
  Domain name: example1.net
  Domain name: example2.net
  Domain name: example3.net
Active clients: 2
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 Ethernet0
 ip address 10.4.9.11 255.0.0.0
 media-type 10BaseT
 ipv6 address 2001:DB8:C18:1::/64 eui-64

Configuration Examples for Implementing DHCPv6

Example Configuring the DHCPv6 Server Function

DHCPv6 clients are connected to this server on Ethernet interface 0/0. The server is configured to use parameters from the DHCP pool called dhcp-pool. This pool provides clients with the IPv6 address of a DNS server and the domain name to be used. It also specifies that prefixes can be delegated from the prefix pool called client-prefix-pool1. The prefixes delegated will have valid and preferred lifetimes of 1800 and 600 seconds. The prefix pool named client-prefix-pool1 has a prefix of length /40 from which it will delegate (sub)prefixes of length /48.

ipv6 dhcp pool dhcp-pool
 prefix-delegation pool client-prefix-pool1 lifetime 1800 600
 dns-server 2001:DB8:3000:3000::42
 domain-name example.com
!
interface Ethernet0/0
 description downlink to clients
 ipv6 address FEC0:240:104:2001::139/64
 ipv6 dhcp server dhcp-pool
!
ipv6 local pool client-prefix-pool1 2001:DB8:1200::/40 48

Example Configuring the DHCPv6 Client Function

This DHCPv6 client has three interfaces: Ethernet interface 0/0 is the upstream link to a service provider, which has a DHCPv6 server function enabled. The FastEthernet interfaces 0/0 and 0/1 are links to local networks.

The upstream interface, Ethernet interface 0/0, has the DHCPv6 client function enabled. Prefixes delegated by the provider are stored in the general prefix called prefix-from-provider.

The local networks, FastEthernet interfaces 0/0 and 0/1, both assign interface addresses based on the general prefix called prefix-from-provider. The leftmost bits of the addresses come from the general prefix, and the rightmost bits are specified statically.

interface Ethernet 0/0
 description uplink to provider DHCP IPv6 server
 ipv6 dhcp client pd prefix-from-provider
!
interface FastEthernet 0/0
 description local network 0
 ipv6 address prefix-from-provider ::5:0:0:0:100/64
!
interface FastEthernet 0/1
 description local network 1
 ipv6 address prefix-from-provider ::6:0:0:0:100/64

Example: Configuring a Database Agent for the Server Function

The DHCPv6 server is configured to store table bindings to the file named dhcp-binding on the server at address 10.0.0.1 using the TFTP protocol. The bindings are saved every 120 seconds. 

ipv6 dhcp database tftp://10.0.0.1/dhcp-binding write-delay 120

The following example shows how to specify DHCP for IPv6 binding database agent parameters and store binding entries in bootflash: 

ipv6 dhcp database bootflash

Example Configuring DHCP for IPv6 Address Assignment

The following example shows how to configure a pool called engineering with an IPv6 address prefix: 

ipv6 dhcp pool engineering
address prefix 2001:1000::0/64 lifetime infinite

The following example shows how to configure A pool called testgroup with three link addresses and an IPv6 address prefix:

ipv6 dhcp pool testgroup
link-address 2001:1001::0/64
link-address 2001:1002::0/64
link-address 2001:2000::0/48
address prefix 2001:1000::0/64 lifetime infinite
end

The following example shows how to configure a pool called 350 with vendor-specific options: 

ipv6 dhcp pool 350
address prefix 2001:1000::0/64 lifetime infinite
vendor-specific 9
suboption 1 address 1000:235D::1
suboption 2 ascii "IP-Phone"
end

Example Configuring the Stateless DHCPv6 Function

This example uses the DHCPv6 function to configure clients with information about the name lookup system. The server is configured with a DHCP pool, which contains name lookup information to be passed to clients. It does not need to contain a prefix pool. This DHCP pool is attached to the access link to customers (Ethernet0/0) using the ipv6 dhcp server command. The access link also has the ipv6 nd other-config-flag command enabled. RA messages sent from this interface will inform clients that they should use DHCPv6 for "other" (for example, nonaddress) configuration information.

ipv6 dhcp pool dhcp-pool
 dns-server 2001:DB8:A:B::1
 dns-server 2001:DB8:3000:3000::42
 domain-name example.com
!
interface Ethernet0/0
 description Access link down to customers
 ipv6 address 2001:DB8:1234:42::1/64
 ipv6 nd other-config-flag
 ipv6 dhcp server dhcp-pool

The client has no obvious DHCPv6 configuration. However, the ipv6 address autoconfig command on the uplink to the service provider (Ethernet 0/0) causes two events to happen:

  • Addresses are autoconfigured on the interface, based on prefixes in RA messages received from the server.
  • If received RA messages have the "other configuration" flag set, the interface will attempt to acquire other (for example, nonaddress) configuration from any DHCPv6 servers.

Additional References

Related Documents

Related Topic

Document Title

IPv6 supported feature list

"Start Here: Cisco IOS Software Release Specifics for IPv6 Features," Cisco IOS IPv6 Configuration Guide

IPv6 basic connectivity

"Implementing IPv6 Addressing and Basic Connectivity," Cisco IOS IPv6 Configuration Guide

IPv6 prefix delegation

  • "Implementing IPv6 Addressing and Basic Connectivity," Cisco IOS IPv6 Configuration Guide
  • "Implementing ADSL and Deploying Dial Access for IPv6," Cisco IOS IPv6 Configuration Guide

IPv6 VPN over MPLS

"Implementing IPv6 VPN over MPLS," Cisco IOS IPv6 Configuration Guide

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

Cisco IOS IPv6 Command Reference

Cisco IOS DHCP relay agent

Configuring the Cisco IOS DHCP Relay Agent

Standards and RFCs

Standards/RFCs

Title

RFC 3315

Dynamic Host Configuration Protocol for IPv6

RFC 3319

Dynamic Host Configuration Protocol (DHCPv6) Options for Session Initiation Protocol (SIP) Servers

RFC 3633

IPv6 Prefix Options for Dynamic Host Configuration Protocol (DHCP) Version 6

RFC 3646

DNS Configuration Options for Dynamic Host Configuration Protocol for IPv6 (DHCPv6)

RFC 3736

Stateless DHCP Service for IPv6

RFC 3898

Network Information Service (NIS) Configuration Options for Dynamic Host Configuration Protocol for IPv6 (DHCPv6)

RFC 4075

Simple Network Time Protocol (SNTP) Configuration Option for DHCPv6

RFC 4242

Information Refresh Time Option for Dynamic Host Configuration Protocol for IPv6 (DHCPv6)

RFC 4649

Dynamic Host Configuration Protocol for IPv6 (DHCPv6) Relay Agent Remote-ID Option

RFC 5460

DHCPv6 Bulk Leasequery

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

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 DHCP for IPv6

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 1 Feature Information for Implementing DHCP for IPv6

Feature Name

Releases

Feature Information

DHCP--DHCPv6 Relay Agent Notification for Prefix Delegation

12.2(33)SCA 12.2(33)SRC 12.2(33)SXI 15.0(1)S

DHCPv6 relay agent notification for prefix delegation allows the router working as a DHCPv6 relay agent to find prefix delegation options by reviewing the contents of a DHCPv6 packet that is being relayed by the relay agent to the client.

DHCP--DHCPv6 Server SNTP, NIS, NIS+, Refresh Timer Options

12.4(15)T

The DHCPv6 server options are part of DHCP stateless autoconfiguration.

DHCPv6 Ethernet Remote ID Option

12.2(33)SRC 12.2(33)SXI 15.0(1)S

This feature adds the remote-ID option to relayed (RELAY-FORWARD) DHCPv6 packets.

IPv6 Access Services--DHCP for IPv6 Relay Agent

12.2(28)SB 12.2(33)SRC 12.2(33)SXI 12.3(11)T 12.4 12.4(2)T

A DHCP relay agent, which may reside on the client's link, is used to relay messages between the client and server.

IPv6 Access Services--DHCPv6 Client Information Refresh Option

12.4(15)T

The DHCPv6 information refresh option can specify an upper boundary for the length of time a client should wait before refreshing information retrieved from DHCPv6.

IPv6 Access Services--DHCPv6 Prefix Delegation

12.0(32)S 12.2(28)SB 12.2(33)SRA 12.2(18)SXE 12.3(4)T 12.4 12.4(2)T 15.0(1)S

The DHCPv6 Prefix Delegation feature can be used to manage link, subnet, and site addressing changes. DHCPv6 can be used in environments to deliver stateful and stateless information.

IPv6 Access Services--DHCPv6 Server Stateless Auto Configuration

12.4(15)T

Hierarchical DHCPv6 for stateless configuration parameters allows a stateless or stateful DHCPv6 client to export configuration parameters (DHCPv6 options) to a local DHCPv6 server pool.

IPv6 Access Services--Stateless DHCPv6

12.2(33)SRA 12.2(18)SXE 12.3(4)T 12.4 12.4(2)T

Stateless DHCPv6 allows DHCPv6 to be used for configuring a node with parameters that do not require a server to maintain any dynamic state for the node.

DHCPv6 Relay--Reload Persistent Interface ID Option

12.2(33)SB 12.2(33)SRC 12.2(33)SXI 15.0(1)S

This feature makes the interface-ID option, which is used by relay agents to decide which interface should be used when forwarding a RELAY-REPLY packet, persistent.

DHCP--DHCPv6 Individual Address Assignment

12.4(24)T

This feature manages nonduplicate address assignment in the correct prefix based on the network where the host is connected.

DHCP--DHCPv6 Relay SSO/ISSU

12.2(33)SRE

SSO and ISSU use redundant hardware, with the active and standby RP each running an instance of the DHCP relay agent.

DHCPv6 Bulk-Lease Query

12.2(58)SE 15.1(1)S

Cisco IOS DHCPv6 relay agent supports bulk-lease query in accordance with RFC 5460.

The following commands were introduced for this feature: debug ipv6 dhcp relay, ipv6 dhcp-relay bulk-lease.

DHCPv6 Relay Source Configuration

12.2(33)SRE 12.2(58)SE

In some networks that use DHCPv6, it may be desirable to configure a stable address (such as a loopback interface) and have the relay use that interface as the source address of relayed messages. The DHCPv6 relay source configuration feature provides this capability.

DHCPv6 Repackaging

12.2(33)SRE 12.2(33)XNE

The DHCPv6 repackaging feature consists of DHCPv6 individual address assignment and stateless DHCPv6.

The DHCPv6 Individual Address Assignment feature manages nonduplicate address assignment in the correct prefix based on the network where the host is connected.

The stateless DHCPv6 feature allows DHCPv6 to be used for configuring a node with parameters that do not require a server to maintain any dynamic state for the node.

DHCPv6 Server - MPLS VPN Support

15.1(2)S

The DHCPv6 server implementation of MPLS VPN support allows a per-pool configuration so DHCPv6 pools can be associated with a VRF instance. The DHCPv6 relay implementation allows the configuration of the destination VRF instance to which the relay messages will be forwarded.

DHCPv6 Server-Relay-Client Support in a VRF Lite Environment

12.2(58)SE

This feature is supported.

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Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

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