topic Re: OpenVPN UDP fails to connect, TCP works fine in Full Fibre

OpenVPN UDP fails to connect, TCP works fine

viktortodorov — Thu, 14 Sep 2017 19:05:19 GMT

I have problems connecting to my VPN service using OpenVPN UDP protocol. TCP connections to that exact server (or any TCP server of the VPN provider) works fine. I tried testing the connection on my neighbour's internet and everything works fine there. So the problem is with the router or Plusnet itself. Both Windows firewall and plusnet firewall are turned Off. I also tried turning on DMZ for my laptop but that didn't change anything again.

I am no networking expert, so can't really think of anything else, called Plusnet they simply said "We dont support these issues".

I don't know whether its udp ports that are blocked (tried a lot of ports, default was 53 tried everything I could think of in the range 5500 - 55000 also) or if somehow Plusnet block all UDP connections?

I am using the Plusnet Hub One router but will test with another router as soon as I get to one.

If anyone has any ideas, please share. Thanks in advance.

Edit: How can I change the MTU value for the Hub One router? I think that might be the problem actually..

Re: OpenVPN UDP fails to connect, TCP works fine

RichardB — Thu, 14 Sep 2017 19:17:38 GMT

I am able to use OpenVPN UDP to access my home server via PN.

I am using a TP Link cable router with a OpenReach as PN did not supply Hub ones when I had FTTC installed.

Regards

Richard

Re: OpenVPN UDP fails to connect, TCP works fine

viktortodorov — Thu, 14 Sep 2017 19:29:14 GMT

Hi I actually just fixed the issue myself.

I changed my MTU via windows cmd to match the MTU of the router. The Hub One seems to have MTU of 1460+28 . Of course I had my MTUs on all connections on my computer set to 1500. I changed the MTU to 1488 and I finally connected to the vpn via udp.

So for anyone having the same problem, this fixed it, not firewall, not DMZ. I have little knowledge of networking so I can't really explain why that was a problem but I want to note that when I contacted technical support earlier they just said "We dont support this". If I may add I almost had to explain what VPN and UDP means to the technical support adviser on the phone before getting the "we dont support this". Really disappointed with the customer service.

Re: OpenVPN UDP fails to connect, TCP works fine

RealAleMadrid — Thu, 14 Sep 2017 19:41:03 GMT

Yes, that sounds like the level of support you get with a low cost ISP.