From: YourPal (dearprudence28@gmail.com)
Date: Mon Feb 18 2008 - 13:13:11 ARST
Hi Group,
I have the following OSPF scenario:
----------(area 1)------------R1---(area 0)
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R5
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----------(area 1)------------R2---(area 0)
When left at default, R5 has the following inter-area routes (all belong to
area 0):
- 139.1.2.0/24 via R2
- 139.1.6.0/24 via R1 & R2
- 139.1.7.0/24 via R1 & R2
- 139.1.11.0/24 via R1
- 139.1.0.0/24 via R1 & R2
The task requires R5 to use R1 to get to the above 5 subnets. If the R1-R5
link (it's a frame relay; R1 uses physical int, R5 uses p2p sub-int) is
down, traffic should be rerouted to R2. "ip ospf cost", "bandwidth",
"virtual-link", "stub", or "nssa" commands are prohibited.
My solution:
R5:
!
access-list 1 permit 139.1.2.0 0.0.0.255
access-list 1 permit 139.1.6.0 0.0.0.255
access-list 1 permit 139.1.7.0 0.0.0.255
access-list 1 permit 139.1.11.0 0.0.0.255
access-list 1 permit 139.1.0.0 0.0.0.255
!
router ospf 1
distance 109 150.1.1.1 0.0.0.0 1 <--- R1's OSPF RID is 150.1.1.1
!
The solution works. R5 prefers all 5 subnets via R1 with AD=109.
To verify, I shutdown R5's p2p sub-int to R1. The OSPF neighbor goes down,
and R5 learns the 5 subnets via R2.
The issue is, after I no shut R5's p2p sub-int and when full adjacency is
formed with R1, R5 again learns all the subnets via R1 (with AD=109) except
the 139.1.2.0/24 which it learns via R2 (with AD=110). I have to do "cle ip
os pro" in order to fix the issue.
139.1.2.0/24 is R2's Fa0/0 subnet.
Can anyone please shed some light on the issue?
Thank you.
BR,
Emil
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