[TriLUG] linux routing example

Frye, Matthew Matthew.Frye at rexhealth.com
Wed Oct 29 13:27:18 EST 2003


> ----------
> From: 	Jason Tower[SMTP:jason at cerient.net]
> Reply To: 	Triangle Linux Users Group discussion list
> Sent: 	Wednesday, October 29, 2003 12:48 PM
> To: 	Triangle Linux Users Group discussion list
> Subject: 	Re: [TriLUG] linux routing example
> 
> 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
> 
Why not mux the two ifs together so only one source if is visible from the
outside?  The router could do that.  Did they just want the bandwidth, or
did they want the two to be visible differently on the outside?  Either way,
you could set the bandwidth and filter the traffic accordingly, no?

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