From: Jason Madsen (madsen.jason@gmail.com)
Date: Mon Nov 03 2008 - 11:49:16 ARST
Traffic actually did leave the local router and then of course it was
unroutable at the neighbor. I enabled deb ip pack 100 with ACL 100 as a
permit icmp any any and saw that it was doing this. It definitely didn't
source with the lowest IP either. I initially had 10.10.10.10 and
20.20.20.20 on my two interfaces and in that case it always chose
20.20.20.20.
With that result I thought maybe it used the highest IP, so I changed
20.20.20.20 to 19... and I also tried 30... and even 100...and got different
results .
As you mentioned it probably doesn't matter. I was just curious if there
was an logic behind the selection process.
Thanks,
Jason
On Mon, Nov 3, 2008 at 4:27 AM, Marko Milivojevic <markom@markom.info>wrote:
> > I was trying to determine what method if any routers
> > use to determine the source address used if/when the destination address
> is
> > not directly connected or in the routing table.
>
> The router "should not" try to generate traffic if there is no route
> for the destination. As we all probably know, it does :-). However,
> it's not really relevant, as this traffic is not leaving the router,
> it's being dropped as unroutable. While I don't think it's really
> relevant which interface it "uses" in this case, I believe it's using
> the one with the lowest IP address.
>
> --
> Marko
> CCIE #18427 (SP)
> My network blog: http://cisco.markom.info/
Blogs and organic groups at http://www.ccie.net
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