MPLS Traceroute vs Ping Test

[galo]

If the CE of a MPLS VRF is not aware of the PE loopbacks is it possible for an end to end traceroute across the VPN network gear to fail?

[Harold Ritter · Accepted solution]

It is indeed possible to traceroute from one CE to another even if the CE is not aware of the ip addresses in the MPLS VPN core (this is usually the case).

Bear in mind that the core network usually doesn't know the ip addresses used by the MPLS VPN customers. Since the core routers have no connectivity to the user address space They use the outgoing label to encapsulate the ICMP TTL expire messages to forward it to the egress PE, which in turn forwards it back to the originator.

Let me know if I answered your question,

[galo]

Yes, thanks so much!