VCCV is supported on S-PE nodes configured for MS-PW and PW redundancy. In this case, S-PE terminates the in-band or out-of-band (IP-routed) VCCV ping (echo reply) and can generate VCCV ping (echo request) toward the dynamic section of the PW segment.
To configure an S-PE for MS-PW and pseudowire redundancy, an explicit endpoint is required to configure the service. Only one explicit endpoint is supported. The first PW segment must be configured with a static inner label under an implicit endpoint. The second PW segment can be created as either a redundant or non-redundant PW using the explicit endpoint.
A VLL service is in MS-PW and PW redundancy mode as long as there is one PW segment with an explicit endpoint configured.
On S-PE nodes configured for MS-PW and PW redundancy, each segment of the PW can be configured with its own independent control word. The control word of the dynamic segment does not have to match the control word of the static segment for traffic to flow. The control word is automatically inserted or removed from the packets as they are switched from one segment to the other based on the control word configuration for each segment.
From an OAM diagnostic perspective, only Type-1 VCCV is supported for the dynamic MS-PW segment, which means that the PW segment must be configured with the control word option. In this mode, the ability to support VCCVs is signaled through the label message and the optional VCCV TLV toward the dynamic segment on the S-PE. The S-PE terminates all VCCV packets arriving on the dynamic segment, then extracts them toward the CSM.