[Nottingham] NIC MACs aliases & IP aliases

[Graeme Fowler]

On Fri, 2009-03-27 at 09:23 +0000, Mike Cardwell wrote:
> Graeme Fowler wrote:
> > You can, however, use the iproute2 toolkit to classify traffic as it
> > arrives and make sure it always leaves via a specified upstream router.
> > This, however, is *not* for the faint of heart and successful boot-time
> > setup varies according to distro of choice...
> 
> You can also use iptables to do it. Eg, if you wanted all outgoing SMTP 
> connections to come from the ip alias 10.0.0.1, this works:

It does, but that clobbers all outbound traffic - using iproute2 you can
classify traffic as it arrives, put it into a given lookup table, and
make sure it leaves via the interface/alias you want and ultimately the
router that it arrived from.

This makes it possible to do active/active systems with multiple
upstream routers (I know that Rackspace do this with their hosted email
service, for example).

Graeme