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Date:      Fri, 15 Nov 2002 12:13:55 +1100 (EST)
From:      Rowan Crowe <rowan@sensation.net.au>
To:        freebsd-isp@freebsd.org
Subject:   Re: Load balancing two unrelated links
Message-ID:  <Pine.BSF.4.21.0211151206000.91083-100000@satin.sensation.net.au>
In-Reply-To: <200211150053.gAF0rNwZ045349@spooky.eis.net.au>

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On Fri, 15 Nov 2002, Ernie Elu wrote:

[...]

> > Then you should install gated (or similar) and enable OSPF on the 
> > FreeBSD machines over the two links. Dynamic routing is the only thing 
> > which can help you.

I've seen this mentioned before, but I have never actually seen _FreeBSD_
do it. I was under the impression that realtime load balancing (ie link
sharing) was more about the kernel, rather than a routing protocol.

Another thing, I don't know whether this will be a practical
issue: because the two links are not identical media you may have
differing latency and usable bandwidth. If you just alternate packets
between links, they may arrive out of order.

I was fooling around with this problem a couple of years ago, and I was
experimenting with route cloning. My memory is a little hazy, but I
*think* it was possible to do something like:

route change -cloning default x.x.x.x

All packets that matched the default route had a specific route installed.
If you can set up something to switch the default between two routes based
on average load, then routes will be cached and all traffic for a specific
IP will go via its chosen link. It's pretty kludgy though, your route
table will be huge, and it will only work well with a large number of
routes (ie useless inbound if you're only sending to a handful of IPs)

Hope this at least inspires, if it doesn't actually help... ;)

Cheers.


--
Rowan Crowe - Melbourne, Australia
www.camrecord.com  www.camdiscover.com  www.heyasl.com  www.sensationbot.com



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