Problem with the PHP

Unanswered Question
Mar 27th, 2008

from the diagram cisco B is having loopback which is advertised by cisco C as label of 45 but the same is advertised by Maipu A as label of implicit null to Maipu B.

Load balacing is done between cisco C -> Cisco A and Maipu A -> Cisco A.

My question is that why cisco C router is advertised by some label .As per cisco it should do the PHP and advertise the loopback of cisco B router to Maipu B with impicit null. But it is not performing. Please provide the solution and send ur comments.

regards

shivlu

I have this problem too.
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mheusing Thu, 03/27/2008 - 09:09

Hi shivlu,

Can you provide the output from "show mpls ldp binding" and "show ip route" from the routers Maipu A and cisco C?

The implicit null label by default is allocated to directly connected networks on MPLS enabled routers. As such I would not assume that any MPLS enabled router in your diagram would choose imp-null for the Loopback network of router cisco B unless there is some summarization configured.

Regards, Martin

Harold Ritter Thu, 03/27/2008 - 09:54

Shivlu,

This can happen if Maipu A has a static route to Cisco B loopback interface address and this route is considered directly connected (i.e. pointing to the physical interface towards Cisco A rather than IP address).

Regards,

Harold Ritter Thu, 03/27/2008 - 10:02

Shivlu,

I just forgot to mention that the behavior exhibited by Cisco C is correct. This router does not send an implicit null label has it is not connected to the advertized FEC.

Maipu A does advertize an implicit null because it thinks it is connected to the FEC because of the static route being considered directly connected.

Regards,

shivlu jain Fri, 03/28/2008 - 08:44

hritter and mheusing

Thanks for your quick reply.But in my network we are using the OSPF. So there is not static route is configured on Maipu A for Cisco B.

As per RFC 3031 implicit null is advertised to the peer only when it sends a request to the peer. So in my scenario can it be possible that Maipu B and cisco C are not sync.

regards

shivlu

Harold Ritter Fri, 03/28/2008 - 08:49

Shivlu,

Could you please provide a "show ip route " from Maipu A. This will help sorting out why an implicit null is being advertised by this router.

Regards,

shivlu jain Fri, 03/28/2008 - 09:18

Cisco-C#sh mpls forwarding-table Cisco-B 32

Local Outgoing Prefix Bytes tag Outgoing Next Hop

tag tag or VC or Tunnel Id switched interface

1897 Untagged Cisco-B/32 3765674 Gi0/1.21 x-x-x-x

Maipu-A#sh mpls forwarding-table | i Cisco-B

L global Cisco-B/32 5253 3 gigaethernet0.48

regards

shivlu

Harold Ritter Fri, 03/28/2008 - 09:23

Shivlu,

As stated before, it is normal behavior for Cisco C to advertise a label different than implicit null.

What I would like to see is the other side (Maipu A). "show mpls for Cisco-B 32" and "show ip route Cisco-B" from Maipu A would be really helpful.

Regards,

shivlu jain Sat, 03/29/2008 - 08:27

hritter thanks for your reply. We had a word with maipu and might be problem at their end.

regards

shivlu

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