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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