[Sheflug] Routing puzzler

[Jonathan <jonathan [at] xxxxxxxxxxxxx>]

Hi all,

Hopefully someone can shed some light on the following conundrum I've been set.

I am working on a server which has two IPs allocated to it. For arguments sake,
let's call them 213.0.0.2 and 193.0.0.0.

The isssue - traffic over the 213 network isn't peered and is MUCH cheaper than
over the 193 network.

What I'm trying to do is figure out how to route traffic so that anything to
213.0.0.2 routes back through 213.0.0.1 and 193.0.0.2 traffic routes through
193.0.0.1.

At the moment, there is a default route set to 193.0.0.1.

I don't have access to the switch/router that things are on. I just need
to make sure that packets are sent the relevant way on return.

Can anyone help me please? I've thought about routed, ipfw source addressing
and even a small child squashed into the 1U case, without success.

This is running on a FreeBSD system, I have access to ipfilter and ipfw. I
would prefer ipfw as I need to throttle bandwidth on the 193 address and I
know how to achieve that with the DUMMYNET subsystem of ipfw.

Apologies if I'm blabbering, I've been staring at my monitor too long!

TIA,

Jonathan
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