[TriLUG] linux routing example

[Jason Tower]

On Wednesday 29 October 2003 12:26, Mike Mueller wrote:
> On Wednesday 29 October 2003 12:05, Jason Tower wrote:
> > the catch was,
> > they wanted to have zero downtime when they made the DNS changes so
> > the web server had to function properly on both T1s simultaneously
> > (the two T1s were from different ISPs and had totally different
> > subnets).  this is harder than it seems at first glance; in order
> > for this to function you have to make sure that traffic "leaves" on
> > the same interface it arrived on, regardless of which route is
> > preferred.
>
> I stumbled on the zero downtime and iso-interface enter/exit
> requirements; if one of the T1 interfaces goes down, what happens to
> responses to queries that entered on the downed interface?  are they
> abandoned or rerouted to the other interface?

even if they were re-routed thru the still active interface, it would 
probably break the tcp connection since the host at the other end would 
see a different source IP.  however, this is only conjecture since i 
have not tried it.

jason