On Thu, Oct 22, 2009 at 10:18:48PM +1100, Karl Auer wrote:
> On Thu, 2009-10-22 at 11:08 +0000, bmann...@vacation.karoshi.com wrote:
> > On Thu, Oct 22, 2009 at 09:44:38PM +1100, Karl Auer wrote:
> > > On Thu, 2009-10-22 at 10:30 +0000, bmann...@vacation.karoshi.com wrote:
> > > > > The RA contains a preference level... maybe that doesn't cut it if
> > > >
> > > > I point you to a fairly common Internet architecture artifact,
> > > > the exchange point... dozens of routers sharing a common
> > > > media for peering exchange.
> > >
> > > And how do they discriminate now, with IPv4?
> >
> > IPv4 has no concept of RA/ND. to make this construct work at
> > all in IPv6, all participants have to turn -off- RA/ND to prevent
> > one or more routers trying to impose their views of addressing
> > on their neighbours.
>
> But my question was not about IPv6. How do IPv4 routers operate in such
> a situation?
>
> Regards, K.
>
exchange design 101.
each connecting router interface is manually configured with an
address of the exchange fabrics IP space.
to establish peering, a router needs to know, at a minimum, the targets
IP address and ASN - and while arp (if enabled) can get the target IP
address,
the ASN has to come via another channel - usually manually aquired.
this is how the exchanges generally work, regardless of IP address
family.
more generally, where there are two or more egress routers from a
broadcast
domain, there will be problems -if- the routers know about each other
-and-
have the ability to try and set the exit rules for all other
participants
sharing the broadcast domain. Hence, with IPv6 and RA/ND, the idea of
"preference" levels ... although in most cases I've experienced where
there
are multiple exit routers - that doesn't work either, since only
subsets of
the nodes on the shared media can use one or the other egress router.
e.g.
all the nodes don't fate-share.
RA/ND was only an 80% solution anyway.
--bill
