barkaHR
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OSPF multi area config with 2 ABRs
Hi, in a OSPF design with 2 areas and 2 ABRs... I have three routers in Area 0. It is hub-and-spoke FR non-broadcast topology. Hub router (R5) is DR, and two spokes (r1 and R4) are ABR between Area0 and Area1. Area1 is one router R6, plus those two ABRs and it is one ethernet segment.
When I ping network X, which is loopback on R6, from R5 hub ping is OK. When I trace same IP I get this:
Tracing the route to 150.1.6.6 (network X)
1 155.1.0.1 24 msec
155.1.0.4 28 msec
155.1.0.1 28 msec
2 155.1.146.6 28 msec * 28 msec
155.1.0.1 and 155.1.0.4 are ABRs. Since the cost to network X are same via R1 nad R4, I have this in routing table:
R5#sh ip ro ospf
155.1.0.0/24 is subnetted, 2 subnets
O IA 155.1.146.0 [110/65] via 155.1.0.4, 00:40:26, Serial0/0/0
[110/65] via 155.1.0.1, 00:40:26, Serial0/0/0
150.1.0.0/16 is variably subnetted, 4 subnets, 2 masks
O IA 150.1.6.6/32 [110/66] via 155.1.0.4, 00:35:27, Serial0/0/0
[110/66] via 155.1.0.1, 00:35:27, Serial0/0/0
O IA 150.1.4.4/32 [110/65] via 155.1.0.4, 00:35:56, Serial0/0/0
O IA 150.1.1.1/32 [110/65] via 155.1.0.1, 00:36:32, Serial0/0/0
In the lab solution guide it shouldn't be two paths to reach network X. Why do I get this ping-pong between two ABRs?
When I ping network X, which is loopback on R6, from R5 hub ping is OK. When I trace same IP I get this:
Tracing the route to 150.1.6.6 (network X)
1 155.1.0.1 24 msec
155.1.0.4 28 msec
155.1.0.1 28 msec
2 155.1.146.6 28 msec * 28 msec
155.1.0.1 and 155.1.0.4 are ABRs. Since the cost to network X are same via R1 nad R4, I have this in routing table:
R5#sh ip ro ospf
155.1.0.0/24 is subnetted, 2 subnets
O IA 155.1.146.0 [110/65] via 155.1.0.4, 00:40:26, Serial0/0/0
[110/65] via 155.1.0.1, 00:40:26, Serial0/0/0
150.1.0.0/16 is variably subnetted, 4 subnets, 2 masks
O IA 150.1.6.6/32 [110/66] via 155.1.0.4, 00:35:27, Serial0/0/0
[110/66] via 155.1.0.1, 00:35:27, Serial0/0/0
O IA 150.1.4.4/32 [110/65] via 155.1.0.4, 00:35:56, Serial0/0/0
O IA 150.1.1.1/32 [110/65] via 155.1.0.1, 00:36:32, Serial0/0/0
In the lab solution guide it shouldn't be two paths to reach network X. Why do I get this ping-pong between two ABRs?
ASKER
I understand. Here, I'm sending you some materials. Hope it would help.
topology2.jpg
R1.txt
R4.txt
R5.txt
R6.txt
R5-sh-ip-route-lab-solution.jpg
topology2.jpg
R1.txt
R4.txt
R5.txt
R6.txt
R5-sh-ip-route-lab-solution.jpg
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ASKER
BW on FR links is default. Nothing is changed. So, you are saying that lab solution is wrong? They have only one path to dest.
Like I said before, without seeing the lab document, I can't say what's right and what's wrong. But based on the diagram you posted, it's behaving correctly.
ASKER
ok. thanks.
Without seeing the lab guide and understanding your topology, it's impossible to say why you're seeing two path instead of one.
>Why do I get this ping-pong between two ABRs?
Because you've got two paths to the same network.