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Silver

Problem with the PHP

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

9 REPLIES
Cisco Employee

Re: Problem with the PHP

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

Cisco Employee

Re: Problem with the PHP

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
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México 
Paseo de la Reforma 222 Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
Cisco Employee

Re: Problem with the PHP

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,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México 
Paseo de la Reforma 222 Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
Silver

Re: Problem with the PHP

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

Cisco Employee

Re: Problem with the PHP

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,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México 
Paseo de la Reforma 222 Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
Silver

Re: Problem with the PHP

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

Cisco Employee

Re: Problem with the PHP

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,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México 
Paseo de la Reforma 222 Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
Silver

Re: Problem with the PHP

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

regards

shivlu

Cisco Employee

Re: Problem with the PHP

Cisco B address was also configured on Maipu A ;-)

Regards,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México 
Paseo de la Reforma 222 Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
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