There
is an IPv6-speci?¬?c requirement per RFC 2461 that a router must be able to determine
the link-local address of each of its neighboring routers to ensure that the target address of
a redirect message identi?¬?es the neighbor router by its link-local address. This requirement
means that using a global unicast address as a next-hop address with IPv6 routing is not
recommended.
The Cisco IOS global command to enable IPv6 is ipv6 unicast-routing.You must
enable IPv6 unicast routing before an IPv6-capable routing protocol, or an IPv6 static route,
will work.
Transitioning to IPv6 283
Routing Information Protocol next generation (RIPng) (RFC 2080) is a distance vector
routing protocol with a limit of 15 hops that uses split horizon and poison reverse to prevent
routing loops. RIPng includes the following features:
?– Is based on IPv4 Routing Information Protocol (RIP) version 2 (RIPv2) and is similar
to RIPv2
?– Uses IPv6 for transport
?– Includes the IPv6 pre?¬?x and next-hop IPv6 address
?– Uses the multicast group FF02::9, the all-RIP-routers multicast group, as the
destination address for RIP updates
?– Sends updates on UDP port 521
?– Is supported by Cisco IOS Release 12.
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