Re: RFC4 4861 and unicast router solicitations

[Aleksi Suhonen <Aleksi.Suhonen at tut.fi>]

Hemant Singh (shemant) wrote:
> An RS with a unicast destination is legal as per RFC 4861.  For example,
> first time when a host was initialized, the host sent an RS with mcast
> destination.  Then the host received an RA and the host acquired IPv6
> address(es) and is up and running.  After a while the host detaches from
> the link and reattaches, or the host network interface is disabled by
> admin and enabled again.  In such cases, the host does know the unicast
> destination of the default router.  So the next time the host is enabled
> or reattached, the host can unicast the RS directly to the router.  

How can the host know that it hasn't been reattached to a different 
network during this outage? (Well ... the unicast RS should reveal that 
of course, but a multicast RS would do the same job too.)

If the subnet has several routers present and the host only cares about 
one of them (for whatever reasons, security, configuration, ...) I think 
that might be a good reason to use unicast RS. Or if a mobile host tries 
to identify the network by its occupants.



--
	Aleksi Suhonen