VCCV trace is similar to LSP trace. VCCV trace is used to trace the entire path of a pseudowire (PW) with a single command.
VCCV trace is useful in multi-segment PW (MS-PW) applications where a single PW traverses one or more switched PEs (S-PEs). VCCV trace is an iterative process by which the initiating terminating PE (T-PE) sends successive VCCV ping messages, each message having an incrementing TTL value, starting from TTL=1. The procedure for each iteration is the same as that for VCCV-ping, where each node in which the VC label TTL expires will check the FEC and reply with the FEC to the downstream S-PE or far-end T-PE. The process is terminated when the reply is from the far-end T-PE or when a timeout occurs.
The results of a VCCV trace can be displayed for fewer pseudowire segments of the end-to-end MS-PW path. In this case, the min-ttl and max-ttl parameters should be configured accordingly. However, the T-PE or S-PE will still probe all hops up to the min-ttl value in order to correctly build the FEC of the desired subset of segments.