[c-nsp] RES: Does traffic routing through a PE get an MPLS labeladded/removed?

Leonardo Gama Souza leonardo.souza at nec.com.br
Tue Dec 2 08:31:24 EST 2008


You're right and your SE is wrong.
What he's saying wouldn't be possible as both site 1 and site 4 are out of MPLS domain.
You can see in the VRF routing table the code 'L' (local) and also the VRF CEF table doesn't have any imposed label.

-----Mensagem original-----
De: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-bounces at puck.nether.net] Em nome de TiM
Enviada em: terça-feira, 2 de dezembro de 2008 07:49
Para: cisco-nsp at puck.nether.net
Assunto: [c-nsp] Does traffic routing through a PE get an MPLS labeladded/removed?


In a recent meeting with our Cisco SE, he told me something that doesn't seem right to me.  I'm having trouble finding documentation to support either side though.
Given the following diagram (apologies to console people) - http://tinyurl.com/cisco-mpls It's my understanding that traffic leaving Site 4 and heading to Site 1 will route locally through the VRF and not have any MPLS header(s) added/removed as it routes through PE1.  (Please assume that all sites are in the _same_ VRF, I realise this Cisco diagram is trying to show two seperate VRFs.  That's my problem, I can find no real Cisco discussion of multiple interfaces terminating on the same PE in the same VRF.)

Our Cisco SE says that even routing locally on PE1 from Site 4 to Site 1, ingress traffic will have an MPLS header added, it will then be routed, then the MPLS label popped off again and it'll egress towards Site 4. 
This seems wrong to me, I think it must just be a IPv4 fowarding decision.
 Only if traffic was egressing towards Site 3 or Site 2 would it have (2) MPLS headers attached.

Can anyone point me to Documentation that would answer this question?

I'm sure that ingress traffic is assigned some internal "you're in VRF x"
label, but our SE was clear in stating it would be an MPLS header added and removed, the same information as if it was egressing towards Site 2/3.



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