Description of problem:

This is the same bug as in Fedora:
https://bugzilla.redhat.com/show_bug.cgi?id=734697

In Fedora, this bug has been fixed.

Also in Debian:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=556974

Doing multipath routing with IPv4 works fine, but it doesn't with IPv6:
    # ip -6 route add default nexthop via 2001:470:25:94::1 weight 1 nexthop via 2001:41e0:ff00:47::1 weight 1
    Error: an IP address is expected rather than "2001:470:25:94::1"

Note that the Debian bug doesn't specify it, but the problem happens even if you only specify one path:
    # ip -6 route add default nexthop via 2001:470:25:94::1 weight 1

This should be equivalent to the same command without the "nexthop":
    # ip -6 route add default via 2001:470:25:94::1 weight 1
    Error: an IP address is expected rather than "2001:470:25:94::1"

Again, this works perfectly fine with IPv4.

How reproducible:
    100%

Steps to Reproduce:
    1. Make sure your network is IPv6 enabled
    2. Try adding a multipath IPv6 route (it doesn't have to have several "nexthop", one is enough to trigger the bug)

Actual results:
Below error output:
Error: an IP address is expected rather than "2001:470:25:94::1"

Expected results:
A working IPv6 multipath route.