This is the first document in the document series Implementing DHCPv6. In this we will see how configure Stateful DHCPv6 in Cisco IOS routers.
In Stateful DHCP the adddress assignment is centrally managed and clients must obtain configuration information such as address autoconfiguration and neighbor discovery that is not available through protocols.DHCPv6 can be implemented in two ways : Rapid-Commit and Normal Commit mode.
In Rapid-Commit mode , the DHCP client obtain configuration parameters from the server through a rapid two message exchange (solicit and reply).
In Normal-Commit mode, the DHCP client uses four message exchanges (solicit, advertise, request and reply). By default normal-commit is used.
In order to use the rapid-commit option, it has to be enabled by both client and server so that it uses two-message exchange.
! version 3.4S ! hostname R1 ! ipv6 unicast-routing ipv6 cef ipv6 dhcp pool test address prefix 2010:AA01:10::/64 lifetime infinite infinite dns-server AAAA:BBBB:10FE:100::15 dns-server 2010:AA01::15 domain-name example.com ! ! ! interface G0/0/1 no ip address duplex auto speed auto ipv6 address 2010:AA01:10::2/64 ipv6 dhcp server test rapid-commit ! end
! version 15.0 ! hostname R2 ! ipv6 unicast-routing ipv6 cef ! interface FastEthernet0/1 no ip address duplex auto speed auto ipv6 address dhcp rapid-commit ipv6 enable ! end
Note: To configure the DHCPv6 in normal-commit mode, use the same command without "rapid-commit" keyword.Also ensure that you explicitly mention the IPv6 enable command in the client interface because, if it is not not enabled, the client will not send a solicit message.
show ipv6 dhcp pool
To display the DHCPv6 pool information, in the DHCPv6 server use this command. The output shows that the number of active clients is 1 and also displays other configuration parameter information, such as domain name server address and preferred life time information.
R1#show ipv6 dhcp pool DHCPv6 pool: test Address allocation prefix: 2010:AA01:10::/64 valid 4294967295 preferred 4294967295 (1 in use, 0 conflicts) DNS server: AAAA:BBBB:10FE:100::15 DNS server: 2010:AA01::15 Domain name: example.com Active clients: 1
show ipv6 dhcp binding
To display the information information about the clients, which includes their DUIDs, IAPDs, prefixes, and preferred and valid lifetimes.
R2#show ipv6 dhcp binding Client: FE80::C801:88FF:FEAC:1C DUID: 00030001CA0188AC0000 Username : unassigned IA NA: IA ID 0x00040001, T1 43200, T2 69120 Address: 2010:AA01:10:0:D16D:EC61:EDCB:8BD1 preferred lifetime INFINITY, , valid lifetime INFINITY,
show ipv6 dhcp interface
This command shows that interface Fa0/1 is configured in client mode and also shows the details of the DNS server address and the domain name that it received from the DHCP server.
R2#show ipv6 dhcp interface FastEthernet1/0 is in client mode Prefix State is IDLE Address State is OPEN Renew for address will be sent in 11:17:16 List of known servers: Reachable via address: FE80::C800:88FF:FEAC:1C DUID: 00030001CA0088AC0000 Preference: 0 Configuration parameters: IA NA: IA ID 0x00040001, T1 43200, T2 69120 Address: 2010:AA01:10:0:D16D:EC61:EDCB:8BD1/128 preferred lifetime INFINITY, valid lifetime INFINITY DNS server: AAAA:BBBB:10FE:100::15 DNS server: 2010:AA01::15 Domain name: example.com Information refresh time: 0 Prefix Rapid-Commit: disabled Address Rapid-Commit: enabled
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