topic Re: VPN connection not working in My Router

VPN connection not working

Jakeyboy — Fri, 24 Jul 2026 18:52:26 GMT

Hi all.

I have switched over to PlusNet today from BT. I have a VPN client running on Router A (the router that has switched to PlusNet) and a VPN server running on Router B at another location. Up until the switch these two routers were communicating fine over OpenVPN on a UDP protocol and a non-standard port. The server uses DDNS and I haven't had a problem until today. I can still connect to the server using my phone using mobile data but I can not connect to it when on Router A's WiFi or from Router A direct. I have tried changing the port to a standard one, tried changing the Router A's DNS, and the MTU packet rate. I've changed NAT passthrough settings. Non of it makes a difference. Does PlusNet have issues with UDP and is it worth changing to TCP? Both routers are ASUS if that helps?

Thanks.

Re: VPN connection not working

Baldrick1 — Fri, 24 Jul 2026 20:03:49 GMT

Moderator's note:
Thread moved from Broadband to My Router

Re: VPN connection not working

MisterW — Sat, 25 Jul 2026 06:26:38 GMT

@Jakeyboy

Does PlusNet have issues with UDP and is it worth changing to TCP?

There isn't any issue with UDP, I have a Wireguard connection to the office using UDP and its fine.

Assuming you didnt have a static Public IP address with BT (you certainly wont with PN) then there's almost no difference as to where your connection is terminated and routed. The only difference will be will be the Public IP address that you are allocated.

Re: VPN connection not working

Dan_the_Van — Sat, 25 Jul 2026 06:44:54 GMT

@Jakeyboy

I have used openVPN with my choice UDP port in the past with no issues, I've since adopted Wireguard again using my choice of UDP port. I have used both router hosted VPN server and dedicated VPN server on my local network.

At a basic level with ICMP echo enabled on the routers are they able to ping each other?

Re: VPN connection not working

Jakeyboy — Sat, 25 Jul 2026 10:37:48 GMT

Thanks for your help.

I can get Router B to successfully ping Router A. But Router A (where the service was switched to PlusNet) cannot ping Router B. I'm so confused. Connecting to the VPN server on Router B works from my phone on cellular using the exact same config file. I've now tried setting up the profiles again from scratch still with no luck. I've also tried setting up a server on Router A and can also connect to that one from cellular.

I've also seen that there is a PlusNet firewall that is set to high and to change this to low/off. But I can't see how to do that and wonder if that is deprecated setting?

Thanks,

Re: VPN connection not working

Dan_the_Van — Sat, 25 Jul 2026 10:58:21 GMT

I've also seen that there is a PlusNet firewall that is set to high and to change this to low/off. But I can't see how to do that and wonder if that is deprecated setting.

For new accounts the plusnet account based firewall was removed, so it should no longer be available, it is found here, https://www.plus.net/member-centre/broadband/firewall but the link may not work.

If I recall the plusnet account based firewall was only for TCP ports so that should not be the issue with ping, just allowing the router to respond to ping or putting a device in the DMZ was all that was required. The routers Firewall would be blocking ICMP.

ping was just intended to check to see if the routers could see each other, what about trying a traceroute to check the route.

Re: VPN connection not working

MisterW — Sat, 25 Jul 2026 11:01:00 GMT

@Jakeyboy

I've also seen that there is a PlusNet firewall that is set to high and to change this to low/off. But I can't see how to do that and wonder if that is deprecated setting?

The firewall is a legacy function and hasnt been part of the functionality on new accounts for a year or so. In any case it only affects incoming connections.

Does router B have an IPv6 address by any chance ? Is it possible that your phone is connecting the VPN using IPv6 ?

Re: VPN connection not working

Jakeyboy — Sat, 25 Jul 2026 11:14:47 GMT

Hi. Both routers have Ipv6 turned on, however "enable Ipv6 Server mode" is switched off on the VPN profile.

My phone when connected to Router B however does return the Ipv6 server address rather than the IP address though.

Re: VPN connection not working

MisterW — Sat, 25 Jul 2026 11:20:02 GMT

Both routers have Ipv6 turned on

but Plusnet dont currently support IPv6 ! Its only in trial for existing customers with a static IP

Does router B actually have a public IPv4 address ?

however "enable Ipv6 Server mode" is switched off on the VPN profile.

Not being familiar with OpenVPN I dont know the significance of that ?

Re: VPN connection not working

Jakeyboy — Sat, 25 Jul 2026 12:07:05 GMT

Thanks for all your help. I did wonder if an IPv6 mismatch was the issue when I found out PlusNet don't yet support it. I tried completely disabling IPv6 from Router A (PlusNet) and updated the VPN client config to be "proto udp4" but still with no luck. So I did some digging on Router B. It gets it's service from an alt-net called YouFibre. They do provide an IPv4 address but it is CGNAT and not routable. So it looks like we'll need to purchase a Static IP add-on with YouFibre. Is that correct? Sorry I'm not overly technical.

Have PlusNet indicated when IPv6 is coming or is there any space left on the trial?

Thanks,

Re: VPN connection not working

MisterW — Sat, 25 Jul 2026 12:42:16 GMT

@Jakeyboy

They do provide an IPv4 address but it is CGNAT and not routable. So it looks like we'll need to purchase a Static IP add-on with YouFibre.

I can confirm that, a colleague has a Youfibre connection and had to purchase a static IP.

Have PlusNet indicated when IPv6 is coming or is there any space left on the trial?

I the recent batch of trialists were added a week or so ago. The trials is currently only on the 'high touch' (static IP) network. The low-touch (dynamic IP) trial isnt far away I believe but no dates yet.

You could try adding a post to https://community.plus.net/t5/IPv6-Trial/Request-to-join-the-IPv6-Trial

Re: VPN connection not working

Jakeyboy — Sat, 25 Jul 2026 12:45:33 GMT

Thanks for all your help on this. I was a bit naive to IPv4/IPv6 so this has been an interesting learning curve.

I'll definitely request access to any testing.

Thank you.

Re: VPN connection not working

MisterW — Sat, 25 Jul 2026 12:55:00 GMT

Yes, I've been on the trial for a few months and have found IPv6 a steep learning curve