The 7450 ESS, 7750 SR, and 7950 XRS routers support end to end VCCV Ping and VCCV trace between a segment with a static MPLS-TP PW and a dynamic T-LDP segment by allowing the user to specify a target FEC type for the VCCV echo request message that is different from the local segment FEC type. That is, it is possible to send a VCCV Ping / Trace echo request containing a static PW FEC in the target stack TLV at a T-PE where the local egress PW segment is signaled, or a VCCV Ping or Trace echo request containing a PW ID FEC (FEC128) in the target stack TLV at a T-PE where the egress PW segment is a static MPLS-TP PW.
Note that all signaled T-LDP segments and the static MPLS-TP segments along the path of the MS-PW must use a common associated channel type. Because only the IPv4 associated channel is supported in common between the two segments, this must be used. If a user selects a non-IP associated channel on the static MPLS-TP spoke SDP, then vccv-ping and vccv-trace packets are dropped by the S-PE.
The target-fec-type option of the vccv-ping and vccv-trace command is used to indicate that the remote FEC type is different from the local FEC type. For a vccv-ping initiated from a T-PE with a static PW segment with MPLS-TP parameters, attempting to ping a downstream FEC128 segment, then a target-fec-type of pw-id is configured with a static PW type. In this case, an assoc-channel type of non-ip is blocked, and the other way around. Likewise the reply-mode must be set to control-channel. For a vccv-ping initiated from a T-PE with a FEC128 PW segment, attempting to ping a downstream static PW FEC segment, a target-fec-type of static is configured with a pw-id PW type, then a control-channel type of non-ip is blocked, and the other way around. Likewise the reply-mode must also be set to control-channel.
When using VCCV Trace, where the first node to be probed is not the first-hop S-PE. the initial TTL must be set to >1. In this case, the target-fec-type refers to the FEC at the first S-PE that is probed.
The same rules apply to the control-channel type and reply-mode as for the vccv-ping case.