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IPv6 Training (Cisco): How to Configure a Cisco Delegating Router for Prefix Delegation Hot

Added: 08/18/2008, Hits: 10,022, Rating: 0, Comments: 0, Votes: 0
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Now in order, to get a Cisco router’s downstream interface to act like a Delegating Router (DHCPv6 Server) that performs Prefix Delegation for a specific Requesting Router (DHCP Client); and also for a group RR’s (DHCP clients) by using a DHCP for IPv6 configuration pool, you will need to complete the following 10 steps:

  1. Router>enable

  2. Router#configure terminal

  3. Router(config)#ipv6 dhcp pool poolname

  4. Router(config-dhcp)#domain-name domain

  5. Router(config-dhcp)#dns-server ipv6 address of DNS server

  6. Router(config-dhcp)#prefix-delegation ipv6-prefix/prefix-length client-DUID [iaid] [lifetime]

  7. Router(config-dhcp)#prefix-delegation pool poolname [lifetime {valid-lifetime | preferred-lifetime}]

  8. Router(config-dhcp)#exit

  9. Router(config)#interface type number

  10. Router(config-if)#ipv6 dhcp server poolname

Steps Explained

Step #1: Router>enable

Puts the router into Privileged Exec mode

Step #2: Router#configure terminal

Puts the router into Global Configuration mode

Step #3: Router(config)#ipv6 dhcp pool local

Is used to configure a DHCP for IPv6 server configuration information pool named “local” and also places the DR router into DHCP for IPv6 pool configuration mode.

Step #4 Router(config-dhcp)#domain-name

Is used to specify that all RRs (DHCP clients) will use the domain name “”.

Step #5 Router(config-dhcp)#dns-server 2001:0DC8:4000:4000::52

Is used to indicate the DNS server (by its IPv6 address) that will be available to Requesting Routers (RR’s) / DHCP clients.

Step #6 Router(config-dhcp)#prefix-delegation 2001:0DC8:1463::/48 0007000700F1A6E070D01

Is used to specify that the manually configured numeric IPv6 prefix of “2001:0DC8:1463::/48” will only be delegated to the RR (DHCP client) that has the Identify Association Identifier (IAID) of “0007000700F1A6E070D01”. In other words, in this step, you are specifying that the DR (DHCP server) only give a certain IPv6 prefix to a specific RR (DHCP client).

Step #7 Router(config-dhcp)#prefix-delegation pool domain-prefix-pool lifetime 3600 60

Is used to specify that the IPv6 local prefix pool named “domain-prefix-pool” be used for IPv6 Prefix Delegation for RRs (DHCP clients) period. In other words, in this step, you are specifying that the Delegating Router (DR) use the “domain-prefix-pool” to delegate IPv6 prefixes to all other Requesting Routers (RRs).

Now just in case if you were wondering, the word “lifetime” is used to configure the IPv6 prefix lifetimes. But, remember if you use the word “lifetime” with the “prefix-delegation pool” command; you will have to configure the “valid –lifetime” (3600) and the “preferred-lifetime” (60) options.

The “valid –lifetime” (3600) option is used to indicate the time allowed (in seconds) that a IPv6 prefix from the “prefix-delegation-pool” will stay valid for a Requesting Router (RR) to use; and the “preferred-lifetime” (60) option is used to indicate the time allowed (in seconds) that the IPv6 prefix given to a RR from the “prefix-delegation-pool” will stay preferred on the RR.

Step #8 Router(config-dhcp)#exit

Allows, the router to exit DHCP for IPv6 pool configuration mode, and re-enter Global Configuration mode.

Step #9 Router(config)#interface serial 0/0

Allows, the DR to enter interface configuration mode for the serial 0/0 interface.

Step #10 Router(config-if)#ipv6 dhcp server prefix-delegation-pool

Is telling the DR router’s serial 0/0 interface that it is going to perform like a DHCPv6 server and to use the IPv6 local prefix pool named “domain-prefix-pool” for Prefix Delegation. Another way of saying it is, in step 10, you are enabling the DHCP for IPv6 service on the serial 0/0 interface which is going to use the IPv6 local prefix pool named “domain-prefix-pool” for Prefix Delegation for Requesting RR’s.

I invite you to visit my website at where you’ll find the latest information regarding Cisco IPv6 Design and Implementation Techniques. And, also learn more about the new "Cisco IPv6 Video Accelerated Training Course" which contains over 3000 videos that will teach you all you need to know about Designing, Building, and Deploying Cisco IPv6 networks. (Guaranteed)

To your success,

Charles Ross
CCNP #CSCO10444244

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