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To: freebsd-hackers@freebsd.org
Subject: Fault-tolerant network with 2 ethernets
Date: Wed, 22 Jan 1997 15:51:30 -0800
From: John Polstra <jdp@polstra.com>
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This is probably a routing 101 question. But I've never had to do much
with routing, so I could use some advice.
A client wants a fault-tolerant LAN setup like this:
ethernet A (100BaseT)
---+------+------+------+------+------+---
| | | | | |
host host host host host host
| | | | | |
---+------+------+------+------+------+---
ethernet B (100BaseT)
The goal is that either ethernet could go down, yet all the hosts could
still talk to each other. Or, one of the ethernet cards on a host could
go down, and it could still talk to all the other hosts. In either
case, it has to happen automatically, without manual intervention. Load
balancing isn't a goal, just fault-tolerance.
At first I was hoping that routed could do this for me, without
the applications even being aware of it. But now I'm not so sure.
Each ethernet will have to have its own IP network number (right?),
and so each host will have to have 2 IP addresses. A given packet
will be addressed to only a single IP address, and that implies
it's headed for a particular ethernet. If that ethernet is down,
all addresses on it are down, and the packet won't be delivered
no matter what routed does.
Is this analysis correct? Is there a simple way to get what I want?
How about a non-simple way?
--
John Polstra jdp@polstra.com
John D. Polstra & Co., Inc. Seattle, Washington USA
"Self-knowledge is always bad news." -- John Barth