Date: Thu, 23 Jan 1997 02:33:27 -0600 From: Chris Csanady <ccsanady@me.bla.com> To: John Polstra <jdp@polstra.com> Cc: freebsd-hackers@freebsd.org Subject: Re: Fault-tolerant network with 2 ethernets Message-ID: <199701230833.CAA28531@me.bla.com> In-Reply-To: Your message of Wed, 22 Jan 1997 15:51:30 -0800. <199701222351.PAA04715@austin.polstra.com>
next in thread | previous in thread | raw e-mail | index | archive | help
>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? I have been thinking about this for a bit, but all I could come up with is a really sick solution. I'm sure its not worth much, and may not even work, but I'll share it anyway. :) To start with, the different interfaces will be on different networks as you describe. But then you delete the 2 network routes, and add 2 default routes to each interface on the router(s). The router would have to have to know about the network topology, and the machines themselves would have to be configured to forward packets. Then everything would (hopefully) be taken care of via ICMP redirects... Anyway, not a very efficient or scalable solution. Or one I would try.. ;) Chris >-- > John Polstra jdp@polstra.com > John D. Polstra & Co., Inc. Seattle, Washington USA > "Self-knowledge is always bad news." -- John Barth >
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199701230833.CAA28531>