# Standard RADIUS IPv6 Attributes for IPv6 Neighbor Discovery Router Advertisements and DHCPv6 Prefix Delegation Configuration

When an E Series router is configured for IP version 6, it uses router advertisements to announce its presence to other nodes connected to it. Hosts discover the addresses of their neighboring routers by listening for these advertisements. When the routing protocol process first starts on the server router, the server sends router advertisement packets every few seconds. Then, the server sends these packets less frequently. The server responds to route solicitation packets it receives from a client. The response is sent unicast, unless a router advertisement packet is due to be sent out momentarily. IPv6 supports the following router advertisement mechanisms:

- ICMPv6 Neighbor Discovery router advertisements
- DHCPv6 Prefix Delegation
- ICMPv6 Neighbor Discovery router advertisements followed by DHCPv6 Prefix Delegation

The AAA service on the router stores the prefixes that it receives from the RADIUS server during the PPPv6 authentication phase. After the PPPv6 link is established between the subscriber and the B-RAS application running on the router, the router receives the ICMPv6 router solicitation message, the DHCPv6 Solicit message, or both of them based on the prefix advertisement mechanism. In previous releases, you were not able to configure the RADIUS attribute or VSA to be used for IPv6 Neighbor Discovery router advertisements and DHCPv6 Prefix Delegation through the CLI. As a result, the IPv6-NdRa-Prefix attribute returned in the Access-Accept message was used for IPv6 Neighbor Discovery router advertisements and the Framed-IPv6-Prefix RADIUS attribute in the Access-Accept message was used for DHCPv6 Prefix Delegation.

In this release, you can control the RADIUS IETF attribute or VSA to be used for IPv6 Neighbor Discovery router advertisements and DHCPv6 Prefix Delegation by using aaa ipv6-nd-ra-prefix framed-ipv6-prefix and aaa dhcpv6-delegated-prefix delegated-ipv6-prefix commands, respectively, in Global Configuration mode on each virtual router.