AEAD Decrypt error: bad packet ID on openvpn using UDP

Question

having some sort of Decrypt error when using openvpn as UDP to connect to server, having this :

Mon Apr 22 17:46:17 2019 AEAD Decrypt error: bad packet ID (may be a replay): [ #49607 ] -- see the man page entry for --no-replay and --replay-window for more info or silence this warning with --mute-replay-warnings
Mon Apr 22 17:46:34 2019 AEAD Decrypt error: bad packet ID (may be a replay): [ #51909 ] -- see the man page entry for --no-replay and --replay-window for more info or silence this warning with --mute-replay-warnings
Mon Apr 22 17:46:50 2019 AEAD Decrypt error: bad packet ID (may be a replay): [ #54482 ] -- see the man page entry for --no-replay and --replay-window for more info or silence this warning with --mute-replay-warnings

If using TCP, getting no problem but I really need to use UDP as openvpn. Is there a way to solve this kind-of error problem?

Solution

If the MTU is 1500, add mssfix 1431 at the bottom of your *.ovpn.

Explanation: get the credit from James Yonan's explanation, who's the owner of OpenVPN

With a TUN-style tunnel over UDP using the default TLS options, the per-packet overhead is:

• 41 bytes security layer overhead (includes packet tag (1), HMAC-SHA1 signature (20), initialization vector (16), sequence number (4))
• 28 bytes tunneling overhead (includes IP + UDP header)
• Total: 69 bytes per packet