IPv6 Training (Cisco): How to Configure a Cisco Delegating Router for Prefix Delegation
Added: 08/18/2008,
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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:
Router>enable
Router#configure terminal
Router(config)#ipv6 dhcp pool poolname
Router(config-dhcp)#domain-name domain
Router(config-dhcp)#dns-server ipv6 address of DNS server
Router(config-dhcp)#prefix-delegation pool poolname [lifetime {valid-lifetime | preferred-lifetime}]
Router(config-dhcp)#exit
Router(config)#interface type number
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.
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.
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