IPv6 - RIPng metric offset

Here is the topology, use whatever DLCI's and interfaces you want:

R4 is learning these routes from BB2:

R 2001:205:90:31::/64 [120/2]
via FE80::CE03:8FF:FE9C:0, FastEthernet2/0
R 2001:220:20:3::/64 [120/2]
via FE80::CE03:8FF:FE9C:0, FastEthernet2/0
R 2001:222:22:2::/64 [120/2]
via FE80::CE03:8FF:FE9C:0, FastEthernet2/0

The task is to force R5 to use the serial link instead of the frame-relay link to reach these networks. Let's look at R5 right now:

R5#show ipv6 route

R 2001:205:90:31::/64 [120/3]
via FE80::CE01:8FF:FE9C:0, Serial1/1
via FE80::CE01:8FF:FE9C:0, Serial1/0.54
R 2001:220:20:3::/64 [120/3]
via FE80::CE01:8FF:FE9C:0, Serial1/1
via FE80::CE01:8FF:FE9C:0, Serial1/0.54
R 2001:222:22:2::/64 [120/3]
via FE80::CE01:8FF:FE9C:0, Serial1/1
via FE80::CE01:8FF:FE9C:0, Serial1/0.54

As you can see it's currently load sharing between the two 3-hop routes. How can we make the serial link more preferred? We can use an offset. It's not like the offset in rip for ipv4, but it works similar:

R5(config)#int s1/0.54
R5(config-subif)#ipv6 rip RIPNG metric-offset 2

Now let's take a look at our routes:

R5#show ipv6 route

R 2001:205:90:31::/64 [120/3]
via FE80::CE01:8FF:FE9C:0, Serial1/1
R 2001:220:20:3::/64 [120/3]
via FE80::CE01:8FF:FE9C:0, Serial1/1
R 2001:222:22:2::/64 [120/3]
via FE80::CE01:8FF:FE9C:0, Serial1/1

Trace from R3:

R3#trace 2001:205:90:31::1

Type escape sequence to abort.
Tracing the route to 2001:205:90:31::1

1 FEC0:CC1E:1:35::5 24 msec 32 msec 32 msec
2 FEC0:CC1E:1:45::4 8 msec 44 msec 16 msec
3 2001:205:90:31::1 56 msec 16 msec 60 msec
R3#

Easy!

I first started out thinking offset-list but I ran into a couple issues. First you can't make ipv6 standard ACLs, at least I couldn't find a way. Then before attempting to use ipv6 prefix lists I thought I would check out what commands were available under an interface for RIPng:

R5(config-subif)#ipv6 rip RIPNG ?
default-information Configure handling of default route
enable Enable/disable RIP routing
metric-offset Adjust default metric increment
summary-address Configure address summarization

This is where I noticed the metric-offset. In addition there is no offset list under router config mode:

R5(config-subif)#ipv6 router rip RIPNG
R5(config-rtr)#?
default Set a command to its defaults
distance Administrative distance
distribute-list Filter networks in routing updates
exit Exit from IPv6 routing protocol configuration mode
maximum-paths Forward packets over multiple paths
no Negate a command or set its defaults
poison-reverse Poison reverse updates
port Port and multicast address
redistribute Redistribute IPv6 prefixes from another routing protocol
split-horizon Split horizon updates
timers Adjust routing timers

Didn't even need the DocCD!