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OpenVPN

Fix openvpn mbuf packet dropped

Written by Mirabellette / 11 april 2018 / no comments

Hello everyone

I hope you are going great and everything was fine for you.

Use case

I have an openvpn daemon running with TCP on 443 port on a Debian system. I got thousands of error messages since months about MBUF packet dropped. The message was

openvpn MBUF: mbuf packet dropped

It occurs only if you use openvpn over TCP. I know it is considered to be a bad practice because it unneeded traffic but you have to make choice.

What I do

After hours of research, I was able to fix it. I add this two lines to the server configuration file:

tcp-queue-limit 4096
bcast-buffers 4096

Now, you have to restart openvpn with this command : systemctl restart openvpn or service openvpn restart if systemd isn't installed on your system.
You should not see this message in log anymore \o/ and get a little bit more stable connection thanks to the undropped packet.

Sources

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Classified in : OpenVPN / Tags : none

Specific OpenVPN error on Windows 10 "endpoints must exist within the same 255.255.255.252"

Written by Mirabellette / 15 may 2017 / no comments

Hello everyone,

    system
  • debian jessie stable 8.7
  • windows 10 creators update
  • openvpn 2.3.4.5 on the server
  • openvpn 2.4.2 on the client

I recently got a new laptop with windows 10. Obviously, I installed OpenVPN with the correct configuration. When I try to connect it i got an error's message.

if The local and remote VPN endpoints must exist within the same 255.255.255.252

After some hours to find a solution, I finally find it and it is trivial. You just have to

open your open vpn configuration
add "topology subnet"
restart openvpn

vim /etc/openvpn/server.conf
add "topology subnet"
service openvpn restart

* on the client

service openvpn restart

Now, the openvpn client must be able to connect to the server without error.

I hope this article will help you to solve this kind of problem.