Symptom

IKEv2 responder rejects the IKEv2 negotiation after it receives the IKE_SA_INIT exchange request from the initiator and the following error is observed in the output of "debug crypto ikev2": IKEv2:Failed to parse the packet: NAT-T disabled via cli

Conditions

NAT-T disabled on the IKEv2 responder

Workaround

Enable NAT-T on the responder by running the command: "crypto ipsec nat-transparency udp-encapsulation"

Further Problem Description