The MPLS WG Archive

["Amit Goyal \(agoyal\)" <agoyal@cisco.com>]

Hi All,

I have couple of questions regarding the operation of lsp ping and trace
route.

1. If an intermediate router does the FEC aggregation then how lsp ping
works for e.g.

           A -------------- B --------------- C
                              |
                              |---------------- C'

In the above case B does the FEC aggregation for both  C and C'. 
a. Does the lsp ping from A for the aggregated FEC terminates at node B?
b. What if I does lsp ping for FEC corresponding to C' only? Is it possible
to do that, as A is not having label mapping for the C' FEC.

2. In case of different tunnel levels in network topology, the lsp ping
would contain the FEC stack of depth > 1 to get it across the tunnel. If lsp
ping is performed (not trace route) then does the tunnel egress after
stripping of corresponding label stack, forwards the MPLS Echo Request
further or it sends MPLS Echo Reply with the return code 8 "Label switched
at stack-depth" (assuming it has the forwarding information)

Any insight on the above questions would be of great help.

Thanks in advance,
Amit Goyal


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