Access Server: "KEEPALIVE_TIMEOUT" error on VPN Connection with Access Server

Description: When connecting to the VPN to your Access Server, you see the below error in the OpenVPN Connect logs:

[Jan 31, 2024, 15:36:06] Session invalidated: KEEPALIVE_TIMEOUT

Explanation: The message "KEEPALIVE_TIMEOUT" means OpenVPN couldn't send or receive the internal pings it uses to determine whether the tunnel is still functioning. Basically, the OpenVPN packets are dropping for a prolonged period. This occurs when the underlying connection is interrupted, or something goes wrong with the OpenVPN tunnel in such a way that no traffic can pass. Eventually, the keepalive packets don't arrive, requiring a connection reset as the connection is considered dead.

Two possible reasons for this issue are the router ISP has firewall/rule capabilities causing problems, or a firewall with deep packet inspection could detect these packets and cause this problem.

You could do packet captures to see if a firewall kicks the connection out after a predetermined time. It's possible that a firewall solution somewhere (either on the client or server side or in between) sees the connection and lets it continue for a certain amount of time before killing it. It is very likely a network connectivity problem.

If you have additional questions, please submit a ticket.