OpenVPN Support Forum

Hi !

I had installed openvpn server on my raspberry pi.

All works fine in tcp mode when I connect to the server with the android application over wifi or my provider 3G connection.

When I switch server in udp mode, everything is allright over wifi but server don't respond over my provider 3G connection.

So I install Android application Netalyzr ton scan my provider 3G connection and there is some warning :

"The path between your network and our system supports an MTU of at least 1356 bytes, and the path between our system and your network has an MTU of 1444 bytes. The path MTU bottleneck that fails to properly report the ICMP "too big" is between XXX.XXX.XXX.XXX and your host. The path between our system and your network does not appear to report properly when the sender needs to fragment traffic."

So I think there is a MTU issue because my provider have a MTU less than the default one (1500) so I think it is why the server didn't answer when I connect in udp mode.

I read there is some option like fragment or mssfix to fix it but I know fragment is not implement on android client app and I don't know if mssfix works.

I try a lot of configurations files without success reading a lot of posts.

Can anyone help me ? I want to fragment or change the MTU from 1500 to 1350.

Thank you and forgive me for my bad english.

Aworan

aworan wrote:I read there is some option like fragment or mssfix to fix it but I know fragment is not implement on android client app and I don't know if mssfix works.

Try using --link-mtu 1200 on the client.