OpenVPN Syslog errors

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Jord9857
DD-WRT User


Joined: 17 Mar 2021
Posts: 74

PostPosted: Thu Jan 11, 2024 17:07    Post subject: OpenVPN Syslog errors Reply with quote
Hi,

Setup this OpenVPN client months ago from scratch following the guides. Worked for ages until recently, just constantly getting this error in the syslog.

DD-WRT daemon.warn openvpn[1965]: WARNING: Bad encapsulated packet length from peer (5379), which must be > 0 and <= 1768 -- please ensure that --tun-mtu or --link-mtu is equal on both peers -- this condition could also indicate a possible active attack

Just updated the firmware, rebooting and tried changing the NordVPN servers etc but nothing. Firmware: DD-WRT v3.0-r54652 std (12/30/23)

Any help would be great, thanks
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egc
DD-WRT Guru


Joined: 18 Mar 2014
Posts: 12837
Location: Netherlands

PostPosted: Sat Jan 13, 2024 11:10    Post subject: Reply with quote
The most obvious explanation is that it is a port scanning attempt on your port 443.

Is it only this entry in the log or do you have actual problems with the VPN?

_________________
Routers:Netgear R7000, R6400v1, R6400v2, EA6900 (XvortexCFE), E2000, E1200v1, WRT54GS v1.
Install guide R6400v2, R6700v3,XR300:https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=316399
Install guide R7800/XR500: https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=320614
Forum Guide Lines (important read):https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=324087
Jord9857
DD-WRT User


Joined: 17 Mar 2021
Posts: 74

PostPosted: Sat Jan 13, 2024 12:04    Post subject: Reply with quote
Yes, VPN works intermittently, after this message in the logs, it resets the connection and displays this again etc
egc
DD-WRT Guru


Joined: 18 Mar 2014
Posts: 12837
Location: Netherlands

PostPosted: Sat Jan 13, 2024 13:02    Post subject: Reply with quote
Things you can try:
Use another port (if your server allows another port)

Use Link MTU 1500
Use Link MTU 0

Use UDP instead of TCP

But I would first ask Nord, you are paying them and not me Wink

_________________
Routers:Netgear R7000, R6400v1, R6400v2, EA6900 (XvortexCFE), E2000, E1200v1, WRT54GS v1.
Install guide R6400v2, R6700v3,XR300:https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=316399
Install guide R7800/XR500: https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=320614
Forum Guide Lines (important read):https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=324087
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