Could this have been an issue with route summarization, where the
pass-through router (C) had summaries from both sides (couldn't make a
decision). If you disable classless on one router, the route & summary will
be assigned in one direction & the true path to the second router will be
defined.
Phil
----- Original Message -----
From: "John Neiberger" <[EMAIL PROTECTED]>
To: "YY" <[EMAIL PROTECTED]>
Cc: <[EMAIL PROTECTED]>
Sent: Sunday, March 25, 2001 3:01 PM
Subject: RE: IP Classless Revisited (this is just odd...)
> Sure, I'll try that but I don't see why it should matter. As I understand
> it, ip classless affects routing table lookups only and it doesn't care
how
> those routes were installed into the table.
>
> Although, given this behavior, my assumption might be wrong.
>
> Thanks,
> John
>
> > John,
> > Interesting. I think this is due to OSPF, not redistribution problem.
> Can you try running RIP instead of OSPF ?
> >
> > Cheers,
> > YY
> >
> >
> >
> > -----Original Message-----
> > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
> > John Neiberger
> > Sent: Sunday, March 25, 2001 5:28 AM
> > To: [EMAIL PROTECTED]
> > Subject: IP Classless Revisited (this is just odd...)
> >
> >
> > Ok, just when you thought it was safe to go back in the water.... Or
> should
> > I say, just when I thought I understood the behavior of 'ip classess'
and
> > 'no ip classless'.... Let me summarize my lab setup.
> >
> > RouterA-----RouterB------RouterC
> >
> > Pretty simple. AtoB is 10.1.1.0/24, BtoA is 10.1.2.0/24. OSPF is
> running
> > on both links. 'ip classless' is on A and C, but not B initially. On
B
> I
> > see these routes:
> >
> > 10.0.0.0/24 is subnetted, 2 subnets
> > C 10.1.2.0 is directly connected, Serial1
> > C 10.1.1.0 is directly connected, Serial0
> >
> > That's what I expect to see. Then I add a default route on B, 'ip
route
> > 0.0.0.0 0.0.0.0 10.1.1.2'. With no ip classless configured, any
packets
> to
> > unknown subnets of 10.0.0.0/8 should be dropped. I tested it and that
is
> > the case. With 'ip classless' configured, and unknown packets
regardless
> of
> > major network get routed to 10.1.1.2.
> >
> > Now here is what I don't understand. Let's turn off ip classless on B
> > again, then go to Router C and add a default route to null0 and
> > default-information originate to the ospf process. I now see this in
> router
> > B:
> >
> > 10.0.0.0/24 is subnetted, 2 subnets
> > C 10.1.2.0 is directly connected, Serial1
> > C 10.1.1.0 is directly connected, Serial0
> > O*E2 0.0.0.0/0 [110/1] via 10.1.2.2, 00:06:38, Serial1
> >
> > There is indeed a default route. With no ip classless configured, I
> would
> > expect the same behavior as before. If I were to ping 10.5.5.5 the
> packets
> > should be unroutable, but they're not! They get routed to the default
> route
> > whether or not ip classless is configured.
> >
> > Why is a default route learned through a routing protocol treated
> > differently than a manually configured default route? I went through
> this
> > entire process twice and I just don't understand the behavior.
> >
> > What am I missing? I know it's going to be something obvious, but I
> don't
> > see it yet.
> >
> > Ok, I just now tried this: with the ospf external default route still
in
> > the routing table, I pinged 10.5.5.5 and it took the default route.
Then
> I
> > manually added a default static route and the destination became
> unroutable
> > due to 'no ip classless' being configured. Removing the static default
> it
> > becomes routable again.
> >
> > Weird. What's going on?
> >
> > Thanks,
> > John
> >
> >
> >
> >
> >
> > _______________________________________________________
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> >
> >
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>
>
>
>
>
> _______________________________________________________
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