The desc explicitly states this is the count of IPsec replay errors — packets rejected by the anti-replay window because they were duplicate or out-of-sequence. A small baseline of replay errors can occur naturally from network reordering on lossy or asymmetric paths, but a sustained or spiking value is a specific, actionable security signal: it means someone captured and is re-injecting previously-seen encrypted packets, which the anti-replay window is actively blocking. e.g. cpvSaReplayErr staying near zero normally, then spiking during a suspected capture-and-replay attempt against the tunnel.