IPSEC-3-REPLAY_ERROR: IPSec SA receives anti-replay error or %CRYPTO-4-PKT_REPLAY_ERR: decrypt: replay check failed The above or similar error message is caused by when a cisco device detects and mitigates an IPsec replay network attack [RFC6479]. “IP Authentication Header” [RFC4302] and “IP Encapsulating Security Payload (ESP)” [RFC4303] define an anti-replay service that employs a sliding window mechanism. … More VPN Anti-Replay drops