Prefixes Advertised in IPv6 Router Advertisement Messages

By default, router advertisement messages include prefixes configured as addresses on router interfaces using the ipv6 address command. You can use the ipv6 nd prefix-advertisement command to control exactly which prefixes are included in router advertisement messages. Along with which prefixes the router advertisement messages contain, you can also specify the following parameters:

  • Valid lifetime: (Mandatory) The time interval (in seconds) in which the specified prefix is advertised as valid. The default is 2592000 seconds (30 days). When the timer expires, the prefix is no longer considered to be valid.
  • Preferred lifetime: (Mandatory) The time interval (in seconds) in which the specified prefix is advertised as preferred. The default is 604800 seconds (7 days). When the timer expires, the prefix is no longer considered to be preferred.
  • Onlink flag: (Optional) If this flag is set, the specified prefix is assigned to the link upon which it is advertised. Nodes sending traffic to addresses that contain the specified prefix consider the destination to be reachable on the local link.
  • Autoconfiguration flag: (Optional) If this flag is set, the stateless auto configuration feature can use the specified prefix in the automatic configuration of 128-bit IPv6 addresses for hosts on the local link, provided the specified prefix is aggregatable, as specified in RFC 2374.

The following example shows how to configure the prefixes that are advertised in the IPv6 router advertisement messages. 

device(config)# interface ethernet 1/3/1
device(config-if-e1000-1/3/1)# ipv6 nd prefix-advertisement 2001:DB8:a487:7365::/64 1000 800 onlink autoconfig

The no form of the command removes a prefix from the router advertisement messages sent from a particular interface.

Parent topic: IPv6 Neighbor Discovery Configuration