RA for a different router

[Nick Hilliard]

On 21/12/2009 05:11, Ole Troan wrote:
> this is not quite correct. Neighbor Unreachability Detection is the
> mechanism used by a host to detect failure of one of its default
> routers. as a part of NUD a host can detect that a connection doesn't
> make forward progress, e.g not receiving TCP acks or that active probing
> (NS/NA) fails. the latter uses a default timer of 30 seconds, but that
> can be configured by the operator (included in RA messages), down to
> milliseconds. in IPv6 a host can use multiple default routers at the
> same time, so the effect of a single default router failure and the time
> it takes for all hosts to converge varies.

This will make no practical difference for default gateway detection, as
the default gateway is effectively a traffic sink from the point of view of
the client.  So unless you crank up your neighbor solicitation packet rate
to something large (think how this might scale on a large corporate LAN),
it's really not going to help much.  I think I'd prefer to stick with vrrp
et al.  Again there's an issue here of operator control - it's far easier
to control vrrp than a pile of clients running potentially disparate
operating systems.

Nick