LDP OVER VRF

[dpuranik]

I see command

"sh mpls ldp neighbor vrf xxxx"

Why someone need to run LDP over the interface which is the part of VRF?

[Harold Ritter]

This was implemented to support the Carrier supporting Carrier feature. IPv4 + Label has been introduced since and is usually the prefer option to deploy CsC.

For more information about CsC, refer to the following link:

http://www.cisco.com/en/US/partner/products/sw/iosswrel/ps1829/products_feature_guide09186a008012db56.html

For more information on how to deploy CsC using IPv4 + label, refer to the following link:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/120newft/120limit/120s/120s23/fscscl23.htm

Hope this helps,

[k.christov]

By the way, what is the preffered method for transporting lables from the customer carrier

LDP or MP-BGP?

LDP has the advantage that customer carrier must not maintain two routing protocols, as he probably runs OSPF at his PEs and not BGP. If MP-BGP is used it must maintain two separate routing protocols.

[Harold Ritter]

The MP-BGP solution doesn't force you to maintain two routing protocols on the CE. You simply run BGP between the PE and the CE and activate ipv4 + label to propagate label information.

On the other hand, the LDP solution does force you to run an IGP (or static routes) between the PE and the CE as LDP will not assign labels for BGP learnt routes.

The MP-BGP solution is interoperable, whereas the LDP solution is not.

Hope this helps,

[k.christov]

Hi

thanks for the answer

Two routing protocols on the PE's customer carrier. Because these routers mostly run only OSPF if the customer carrier does not provide MPLS VPNs. If the MP-BGP is used this PEs must support BGP to the carrier VRFs and OSPF for their internal routes from the backbone.