I have a question about how to configure "multi-router in a singe
link" environments.
Consider the following topology:
segment1
|
routerA routerB--->(backbone)
| |
+----segment2-----+
and assume that host in segment2 usually communicate with nodes in the
backbone side, but sometimes communicate with hosts in segment1. In
other words, routerB is the "primary" router for hosts in segment2.
Now I have a question. Should routerA advertise RA messages on
segment2?
If A advertises RAs, it will have to issue many redirects, because
traffic from hosts in segment2 usually go to the backbone (based on
the assumption above).
However, if A does not advertises RAs, communication between segment1
and segment2 would fail when routerB died.
So, what should we do?
1. routerA should not advertise RAs on segment2. We should just give
up communication between segment 1 and 2 if routerB dies.
2. routerA should advertise RAs. We should put up with redirects.
3. hosts in segment2 should participate in the routing protocol
running on the segment to know the better router.
Of course, the answer could depend on the precise situation
(e.g. number of hosts in segment2, the ratio of traffic to the
backbone, etc.) But if there has been a generic opinion on this, I'd
like to know it.
I also thought about a possibility to intorude a new RA option
(e.g. containing a router's preference value) to tell the hosts the
better router in the segment. Is this kind of approach worth
considering? (I recalled a discussion on a new RA option that tells
hosts the better router for particular prefixes around December 1998,
and reread the discussion, but I'm not sure if it was exact the same
issue.)
Thanks,
JINMEI, Tatuya
Communication Platform Lab.
Corporate R&D Center, Toshiba Corp.
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