ASA Site-to-Site IKEv1 IPSec VPN recv errors

On a Cisco ASA device, receive errors on an IKEv1 IPSec VPN tunnel usually increase when one of the tests performed during the decapsulation of the ESP fails. These include:

• Anti-replay out of window errors
• Digest errors (packet corrupted)
• Invalid decapsulation length/SA/protocol
• Any other decapsulation failure

To determine the specific reason for a receive error, the use of various debug commands is necessary such as:

debug crypto ipsec
debug crypto isakmp

For additional troubleshooting tips, take a look at ASA troubleshooting IPSec.

Links:

https://forum.networklessons.com/t/cisco-asa-site-to-site-ikev1-ipsec-vpn/825/101?u=lagapides

https://community.cisco.com/t5/vpn/need-explanation-for-ipsec-recv-errors/td-p/1153999

https://www.cisco.com/c/en/us/support/docs/security/asa-5500-x-series-next-generation-firewalls/81824-common-ipsec-trouble.html

https://www.cisco.com/c/en/us/support/docs/security-vpn/ipsec-negotiation-ike-protocols/5409-ipsec-debug-00.html#crypto_isakmp