Subject: (IPng 7018) Re: route distribution via ND

From: Richard Draves <[email-masked]>
Date: Wed, 6 Jan 1999 14:12:09 -0800

> Suppose you have your canonical dual-homed host H on two links L1 and
> L2.  Each link has other, single-homed hosts, or hosts dual-homed to
> L3, and one or more routers.  There may be no router in common on L1
> and L2.  There may be a myriad of destinations for which one link is
> preferred over the other, and not always the same link.

Yes, in a very complex topology the multi-homed host needs a very large
routing table to achieve perfect routing. I think this is inevitable, and
the responsible network administrator can either choose not to build such a
complex topology or to summarize the routing information provided to the
hosts and accept imperfect routing.

> I suggest a new option on neghbor advertisements which would include
> an AS identifier and a metric.  Then a multihomed host which does not
> participate in a routing protocol but which wants to choose the best
> first-hop interface can do an NS (which might also include a new
> option, perhaps containing traffic class information?) on each
> interface and, when the NA replies have the metric option with equal
> AS identifiers, choose the better metric.

I guess I don't understand this. Won't there only be an NA reply if the
destination in question is on-link? The on-link prefix information in RAs
already let a multi-homed host select the correct interface to use to reach
on-link neighbors. Or are you suggesting that routers will respond with NAs
on behalf of destinations to which they know how to route?

Rich
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From: "Matt Crawford" <[email-masked]>
Date: Wed, 06 Jan 1999 16:48:20 -0600

> .. are you suggesting that routers will respond with NAs

Yes, this would fit in under the term "proxy" as used in 2461.  It
may be a burden to be a member of so many multicast groups (all the
solicited-node addresses, in practice) but many routers will
typically be receiving all multicasts anyway.

				Matt