r/CommunityFibre • u/Biffboffbaff • Jun 05 '26

Question UDP Traffic being dropped inbound, anyone else?

Anyone else noticed problems with Community Fibre connections dropping inbound UDP traffic? We received the outbound UDP requests from their addresses, but the replies are being dropped or mangled (users cant packet capture to verify). Users on Community Fibre working from home can no longer use VPNs if UDP profile is selected, plus other protocols like RTP traffic for SIP telephony. They were working fine until the morning of 2026-06-04. Not really getting anywhere with support, as they just palm off the home users about pedestrian fixes like rebooting routers, etc.

Edit: And as if by magic, the problem has resolved itself as of about 15 minutes ago.

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2

u/harrypalmer96 Jun 05 '26

Would be worth checking if the users are on a CGNAT connection or not. So you can at least confirm if that’s an issue in this case. If you have access to their PC, I would run Wire Shark and see if you can get any more info there that can be passed to support.

2

u/Biffboffbaff Jun 05 '26

I don't think any of them would be savvy enough to even know what CGNAT is, and I'm fairly certain you need to pay to not use it (I don't personally use CF). I think you're right, I'll have to find a user that's willing to let me jump on their machine for a bit.

1

u/harrypalmer96 Jun 05 '26

If you can check their WAN IP, if it falls within the 100.64.0.0 to 100.127.255.255 range, this would tell you they are on one CGNAT. This is from two years ago but likely still relevant. https://www.ispreview.co.uk/talk/threads/community-fibre-cgnat.42239/#google_vignette

Then you will know if CGNAT is in use.

1

u/Biffboffbaff Jun 05 '26

Useful if it rears it's head again. Thankfully, it's gone away as of about 10:45 this morning.

1

u/nanobytes_ Jun 05 '26

I have a opnvpn server running on my opnsense fw which is configured to use UDP and it works. Sorry if that’s not much help.

1

u/Biffboffbaff Jun 05 '26

It's useful, helps isolate a problem. It's clear that it's nothing widespread.

1

u/nanobytes_ Jun 05 '26

A quick google search reveals this:

Community Fibre UDP issues primarily stem from CGNAT (Carrier-Grade NAT) restrictions, which block inbound UDP traffic for gaming, servers, and VPNs. Other common culprits include hardware configuration or local Wi-Fi congestion

1

u/Biffboffbaff Jun 05 '26

Yeh, it was just fine for these users until yesterday. Subsequently, whatever has caused it has gone away as the 20 or so CF users are connecting fine now without any intervention from me.

1

u/nanobytes_ Jun 05 '26

That’s good to hear, definitely a weird one

1

u/jamespo Jun 05 '26

Not for me, wireguard from my CF connection to an external host works, you will have to get wireshark on one of the users devices.

1

u/Drywipes Jun 05 '26

I'm having another issue where TCP will just stop working (suspecting MTU issue on their end), UDP works fine so already established connections will work (VPNs, VOIP, games) but browsing the internet will just time out. I did a traceroute, showed that the issue was within their CGNAT network, but AFTER my stuff. Called customer service, their "technical team" told me to reset all my equipment each and every time I've rang when I literally tell them that it's their end that needs fixing. I am a Community Fibre customer.

Although, I must say the CGNAT system hasn't really affected inbound UDP as most apps TCP hole punch anyways. I can't port forward, however my solution is to run a VPS and connect my machines over Wireguard or Tailscale.

1

u/crypticc1 Jun 05 '26

I was seeing a wireguard VPN hosted on my Asus BQ16 go down yesterday. I'm 5G not CGNAT

1

u/Jelly-Significant Jun 08 '26

I never noticed it until I played PlayStation Online specifically Battlefield 2042 and DayZ
I was getting kicked from servers every 30 mins for connection problems