Health check Virtual Circuit Connectivity Verification (VCCV) can be used as a network diagnostic tool or as a network fault-alert tool, and can be configured on up to 16 VPLS domains. Connectivity between VPLS peers can be verified using the health check VCCV feature, which is defined in RFC 5085, Pseudowire Virtual Circuit Connectivity Verification (VCCV).
Health check uses the LSP ping capability to verify connectivity. When the PW is set up, the two peers negotiate the VCCV capabilities, and if they establish a common set, health check becomes operational. If the VCCV capabilities do not match, health check cannot operate.
Health check operates in a single direction, so health checking should be enabled on the LSRs at both ends of the pseudowire in order to verify that traffic can flow bi-directionally between two VPLS peers. For multi-peer full-mesh or hierarchical VPLS networks, VCCV should be enabled on all VPLS peers to verify the entire VPLS network.
VCCV sends health check packets at regular intervals (the default interval is 5 seconds). If health check reaches the threshold for missed responses (the default fault-multiplier is 4), health check logs a message in EMS at the Warning level. Note that this log is not seen with the default log settings and no SNMP (Simple Network Management Protocol) traps are sent. A health check failure does not change the state of the PW, which could remain operationally up and continue to support traffic, depending on the actual problem.
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