[c-nsp] IPV6 in general was Re: Large networks

[Michael K. Smith - Adhost]

> 
> Hi,
> 
> On Thu, Aug 27, 2009 at 10:00:35AM -0700, Michael K. Smith - Adhost
> wrote:
> >  ipv6 address <v6 address>::1/64 anycast
> 
> That's cool.  How exactly does it work?

I haven't been able to find anything specifically on Cisco's website
about how it really works.  Even the tech docs just say it has to do
with geographic locale - the closer one wins.  I'm not sure how the
devices (in this case, FreeBSD boxes running PF) know which is closer,
but they do.  :-)
> 
> I assume that the "anycast" suffix will suppress DAD, and then the
> client will use whichever router answers first on the ND request for
> ::1, and when NUD strikes, the next ND will get the other router?
> 
I read through RFC2373 and it doesn't detail how it works either - it
just specifies what you can and cannot do.  The main point is that
anycast only works on routers, not hosts.  I can tell you that the
router shows that DAD is *not* enabled on either interface.  But, this
is interesting.  When I ping the ::1 address from one of the PF boxes,
the neighbor entry changes from "state" to "reach" which seems to
indicate that the "reach" router is being seen as geographically closer.

Mike