Several IPv6 routers and default gateway choice

[Victor Sudakov]

Hiroki Sato wrote:
> va>
> va> If a FreeBSD host receives router advertisements from several IPv6
> va> routers, on a LAN segment, which would be chosen as the default gateway?
> 
>  One reachable router will be selected based on the default router
>  preference value in RA, which is defined in RFC 4191.  If all of the
>  routers have the same preference, the first one will win.
> 
> va> Can this be used for failover?
> 
>  Yes.
> 
>  Another way to realize failover is to use a common anycast address on
>  multiple routers. For example, a router is always able to have
>  fe80::/64 as an anycast address like this:
> 
>   router# ifconfig igb0 inet6 fe80::/64 anycast
> 
>  and you can simply configure fe80::/64 as the default router on the
>  hosts.  Multiple routers with the same fe80::/64 can coexist on the
>  same segment, and hosts will choose one of them with no further
>  configuration.  A caveat in this case is that the first router always
>  wins and there is no knob to set the preferences across the routers
>  with the same anycast address configured.

Thank you Hiroki, this was very informative and useful.

Can any IPv6 unicast or link-local address be configured as an anycast
address of a router? Is this a replacement for VRRP and carp(4)? 

-- 
Victor Sudakov,  VAS4-RIPE, VAS47-RIPN
2:5005/49 at fidonet http://vas.tomsk.ru/
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