Community Fibre - IPv4 port forwarding and IPv6

I joined CF a few weeks ago, realised that there was no IPv4 port forwarding so after a few back fourths they eventually enabled it for my account but doing this has stopped the router getting an IPv6 address and in turn stopped my devices also being allocated a public IPv6.

Queried this with CF and I’m told by their Tech Support that it’s either one of the other and that from a WAN point of view I can’t have 1, so it’s 1 or the other.

Now this isn’t that big an issue but while I didn’t have IPv4 port forwarding I configured a few of my device for IPv6 so that I could access them remotely but this now no longer works.

So is what I’m being told correct that from a router point of view it’s one of the other?

If you are unable to get port forwarding on IPv4 working then its due to you are on CGNAT and you wont be able to have Port Forwarding due to how CGNAT works.

The only way to get Port Forwarding is if they move you off CGNAT (which they probably won't if you are not on their 3Gbit package and if it's a new connection which yours is) so unless they are using some voodoo IPv6 stuff to port forward IPv4 (not really an IPv6 expert) but they might be telling you porkies there.

Unless I am wrong which somebody will correct me.

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Paul

I agree with Paul. V likely that you not being able to port forward to using IPv4 is due to CGNAT. You can confirm this by checking whether your WAN IP in your router is the same as that reported by "what is my IP address" type sites on the web. If you're on CGNAT, they will differ.
To be able to port forward here, you need to be taken off CGNAT and given a publicly routable IPv4 address.

This should be completely unrelated to whether they allocate you IPv6 addresses - unless that have done something very odd indeed that I cannot conceive of.

Or unless they have made a policy decision that they will either provide a public IPv4 address or will provide IPv6 but would not provide both. It is unlikely to be a tech limitation but could be a policy of the company.

I have confirmed that IPv4 port forwarding now works, albeit rather clunkily at the moment as my public facing IPv4 address appears to be changing 2-3 times a day, no idea why unless it's settling in.

After they have made this change my router no longer has an IPv6 public address, when I check in the Linksys router the IPv4 is shown but the IPv6 address is just blank and all the devices within my home now only have a link local IPv6 address whereas previously they were being allocated a public facing IPv6 address.

Their support guy said it's one of the other so if I want IPv6 then I'd have CGNAT for IPv4 and if I want port forwarding then IPv6 would be disabled as a WAN device can't have 2 public facing addresses. This is rather strange as he's saying that the 2 from a WAN point of view can't co-exist which isn't correct unless this is a quirk or limitation of their setup?

Anybody with CF who had port forwarding enabled could they check their Linksys router on the Troubleshooting page Diagnostics tab to see if they have both an IPv4 and an IPV6 address?

In reply to a post by iluvnips:

Their support guy said it's one of the other so if I want IPv6 then I'd have CGNAT for IPv4 and if I want port forwarding then IPv6 would be disabled as a WAN device can't have 2 public facing addresses.

That is Ballcocks™. The whole point of dual stack is that you have two addresses. I'm on Aquiss, and my Mikrotik router has both an IPv4 and an IPv6 public IP address.

But it could be to do with how their network is (badly) designed. Maybe they have one part of the network which has a pool of IPv4 addresses but no IPv6; and they have another part of the network with CGNAT and IPv6. Then they tunnel your session to one or the other.

Adding IPv6 to the part of the network with IPv4 addresses should be relatively straightforward, but if they've chosen not to do this, then you're stuck.

In reply to a post by candlerb:

That is Ballcocks™. The whole point of dual stack is that you have two addresses. I'm on Aquiss, and my Mikrotik router has both an IPv4 and an IPv6 public IP address.

I am with CF and also using a MikroTik (Model number in my sig) and I can confirm that I have both a Public IPv4 and IPv6 and they both work great with Port Forwarding.

In reply to a post by candlerb:

But it could be to do with how their network is (badly) designed. Maybe they have one part of the network which has a pool of IPv4 addresses but no IPv6; and they have another part of the network with CGNAT and IPv6. Then they tunnel your session to one or the other.

The OP is on CGNAT due to new customers not on their 3Gbits Package will be put on CGNAT, CF might be doing some Voodoo stuff on IPv6 to get IPv4 Portforwarding to work, but I am just guessing that the OP just got some BS from support that has no clue.

In reply to a post by candlerb:

Adding IPv6 to the part of the network with IPv4 addresses should be relatively straightforward, but if they've chosen not to do this, then you're stuck.

I think its just down to them being of CGNAT and them getting bad support that has no clue.

It is and they do have it proof shown in the screenshot images here: Whats My IP Address - IPv6 Test

As you can see CF can and do provide both IPv4 and IPv6 Addresses fine, just new customers not on their 3Gbit Package will get put on CGNAT.

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Paul

Can you go to WhatsMyIPAddress and once all loaded and detected your IP Addresses, take a screenshot of that page and then send it to me via Private Message and I will see what you have and don't have.

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Paul

In reply to a post by ian72:

Or unless they have made a policy decision that they will either provide a public IPv4 address or will provide IPv6 but would not provide both. It is unlikely to be a tech limitation but could be a policy of the company.

I know new customers not on their 3Gbit Package WILL be put on CGNAT its states this on their site if you go looking.

If Community Fibre hasn't already, but they should state this on their product page so that the possibly new customer will know this before ordering.

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Paul

@PaulKirby, I've sent you a PM as requested.

CF don't advertise the lack of port forwarding on their man website, which is what caught me out when I subscribed.

I had also spoke to their sale team a number of times and told them how I used the internet with my previous supplier. I ended up lodging a complaint and told them that their main website does not make this clear or even highlight that this feature isn't available and as a result they agreed to enable port forwarding on my account but then the ipv6 side looks now to be disabled?

Edited by iluvnips (Mon 11-Dec-23 11:01:10)

Yeah I responded to your PM.

Also the main reason they don't say anything about that fact that Port Forwarding won't work is down to the majority of customers will be fine on CGNAT, it is only when a service on the customers LAN is expecting to receive a connection on a Bound Port is when there starts to be issues.

When I signed up with them about 2.5 years ago I gave them my T&C before I would signup with them, which they agreed to over the phone which then was emailed to me along with what was discussed over the phone along with the new account and package information that we both decided on.

Basically, I needed reassurance all our services that is run here needs to work.

I cannot / wont say what we agreed to due to that is private between them and myself, but I always make sure this agreement remains when I renewed for another 2 years.

But like I said in the PM I think its either just a marketing thing to get new customers to get their top tier package, OR they messed up. But its hard to tell due to I don't know how they run their network.

All I can say is they can have both IPv4 and IPv6 being used over the same WAN due to my connection has both.

But just a heads up, there is no such thing as "enable port forwarding" on your account, that is not how networking works, Port Forwarding is setup on your router, not your ISP. All they did was just give you a Public IP and that is all.

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Paul

Well things get stranger.

This morning I added a child node to help with poor coverage of the WiFi in the kitchen area and after adding that node I've now noticed that the router now gets an IPv6 address with all devices now also get an address based upon the prefix of the routers address i.e. pretty much as it was before I was moved away from CGNAT.

In reply to a post by iluvnips:

Well things get stranger.

This morning I added a child node to help with poor coverage of the WiFi in the kitchen area and after adding that node I've now noticed that the router now gets an IPv6 address with all devices now also get an address based upon the prefix of the routers address i.e. pretty much as it was before I was moved away from CGNAT.

Well that is great news, I knew they were talking rubbish when they said you couldn't have both on the same WAN.

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Paul

Hey, I want to know some more clarity regarding this CGNAT. I know that Community Fibre have made CGNAT by default for all packages except for the 3Gbps service.

Before I read you had to take the 500Mbps to have CGNAT removed by default. I know you cannot do port forwarding on CGNAT.

I have not yet joined Community Fibre due to this worry. I do require port forwarding for certain games and just relying on dedicated servers would be a restriction.

I know they do not make that specifically clear on their website. Do Community Fibre remove CGNAT on their discretion or are they simply rerouting by giving a public IP address?

Quite a few people have claimed that Community Fibre have removed it after threatening to cancel their service. Is this really completely removed? I've also read from other people on the ISPreview forums that after giving them a public IP port forwarding worked but IPv6 stopped working. Now you are saying it is working again.

It makes me wonder why this would happen that after port forwarding is enabled IPv6 stops working (at least initially). I want to know if this is exactly the same thing as those on the 3Gbps service since I've not read any complaints from the 3Gbps users on any forum yet about IPv6 not working since their CGNAT is removed by default.

It makes me wonder why this would happen that after port forwarding is enabled IPv6 stops working (at least initially). I want to know if this is exactly the same thing as those on the 3Gbps service since I've not read any complaints from the 3Gbps users on any forum yet about IPv6 not working since their CGNAT is removed by default.

I'm on the 3Gbps service. I don't need this bandwidth but port forwarding is crucial for me.

IPv4 port forwarding and IPv6 are both working for me. A few weeks ago I had an issue where IPv4 was working fine (including port forwarding) but my router was not receving an IPv6 address. This was resolved after a call to their customer services and a request to clear the MAC cache (I am not sure what this means exactly but I recall reading somewhere that this might help in such a scenario).

In reply to a post by BLaZiNgSPEED:

I know they do not make that specifically clear on their website. Do Community Fibre remove CGNAT on their discretion or are they simply rerouting by giving a public IP address?

I would just phone them up and enquire about joining them and say that if you signed up with them for 24 Months that you would require a Public IPv4 and IPv6 Address due to you run Services that require a Public IP using Port Forwarding.

And if they agree to provide you that if you sign up to 24 Months and also get them to email what you both agreed to so that you can dispute that if they don't provide that.

I signed up over two years ago over the phone and I told them what I required (cannot say what we agreed to) and that I would sign up to 24 months, we both agreed to those terms and they have stuck to them, even when I renewed for another 24 Months.

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Paul

In reply to a post by teshy:

IPv4 port forwarding and IPv6 are both working for me. A few weeks ago I had an issue where IPv4 was working fine (including port forwarding) but my router was not receving an IPv6 address. This was resolved after a call to their customer services and a request to clear the MAC cache (I am not sure what this means exactly but I recall reading somewhere that this might help in such a scenario).

A MAC address (short for media access control address) is a unique identifier assigned to a network interface controller (NIC) for use as a network address in communications within a network segment.

So your Router's WAN Port with have a Unique MAC ID (some allow you to change it) so your Provider will see this MAC Address asking for an IP so it will assign you that IP Address.

Community Fibre call it a Sticky IP, basically its an IP that has been assigned to your Mac Address, which is why you have to have them to clear that MAC if you were to change your Router.

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Paul

Yes, this is a good idea what you're suggesting. But the main problem with this is that I then lose out on the cheaper deals from Uswitch/MoneySuperMarket that often load with Amazon vouchers.

Like teshy mentions that the 3Gbps isn't needed but only signed up to get CGNAT removed as port forwarding is important. Community Fibre are deliberately not making this explicitly clear on the website as they don't want to lose potential customers and also that's their way to get 3Gbps subscribers since they don't know what better way to convince customers to switch to the most expensive package since most people will be more than happy to stick with 500Mbps/1Gbps or even lower tier packages.

Before when I read about 500Mbps minimum that was more reasonable but now to include it only for 3Gbps service is extremely unfair. This was always my fear with a single Altnet only provider as opposed to an Openreach FTTP network where we would've had the choice to choose, which ISP doesn't include CGNAT.

Obviously losing IPv6 will not be a deal breaker for me even if that were to happen. Port forwarding should not be a restriction. Many years ago I had problems with port forwarding with BE Unlimited ISP and that was down to their Thomson router. At least buying new Netgear router at that time resolved port forwarding for me.

But in this particular case changing router won't fix port forwarding as we are behind CGNAT. For me this is a completely new discovery that if it wasn't for reading these forums I would've never had known that this is going to cause problems for opening ports and that'll apply for many customers who are not technically well oriented.

I feel for you, I'm in the exact same boat.

With Plusnet I was happily able to Port Forward and connect to (externally tested) my game servers for Jedi Academy and XEvil, it's a precious nostalgic thing for me.

With CF I tried to set this up the same way, and to my surprise it wasn't working. That's when I found this thread.

I'll be calling them up and referring back to this thread again because they should be able to sort the CGNAT issues without bumping us up to the more expensive packages.

Update; I had a call from them asking how the installation went. I rated it 10 because it was fast and all, then proceeded to ask if they saw my support case which they don't seem to have seen. After a bit of back and forth, they said I should speak with their network team to see if there's anything they can do for the CGNAT issue as I don't need IPV6 if it can work over IPV4. To use their Live Chat (which currently is down), so I'll give it a go tomorrow. All they asked me to do was hold the reset button for 40 seconds (light flashed purple on router, then solid blue after a moment). Will test Port Forwarding again soon but I doubt it did anything.

The number they called from had me a bit worried though; it was identified as "Potential Fraud" from 020 3467 9530. Looks to have been since resolved since I mentioned it to them, but nevertheless. I called the number on Community Fibre's own website (0800 082 0770) to ask if that number (020 3467 9530) was their own, and they said yes and that I reported the Port Forwarding / CGNat issue, so that gave some peace of mind.

Seems they have a bunch of support numbers going about there lol, just a heads up for anyone else. This one in particular seems to be their Sales team though, but it pays to be cautious

https://who-called.co.uk/Number/02034679537
https://www.unknownphone.com/phone/02034679530

So finally got through to LiveChat, but after asking a few times if anything could be sorted they only re-directed me to use the Contact Form on the website instead, so it kind of went in circles. I'll give that a go I suppose. Here's the transcript if anyone wants to see it (I've removed personal address information from the start of the chat)

https://pastebin.com/sZ2YnY4w

That is strange, I have never had any issues getting stuff resolved and I have been with them for a few years now, well only once, where their Tech Support had no clue was a SFP/SFP+ Port was, where they just dumped me on their Customer Support Team, she at least knew what it was, she said she would send all the required information in an email and 3 weeks later, I have still yet to get said email.

I hope you get that email due to the only emails I get from them is the one that contain the invoice LOL

Also found out last week that port 443 (port used for HTTPS) is blocked on IPv6 yet is open on IPv4, so that is strange.

Also their IPv4 is dynamic but is sticky and my IPv4 hasn't changed for over a year or two, even when the router or modem has been turned off all day, where as their IPv6 (via their prefix) does, like every 7 days, why that couldn't be sticky like their IPv4 Addresses.
Not that IP changes is an issue due to DDNS updating within 60 seconds (even on Googles DNS) and propagation in most cases about the same.

BUT, you can cheat by using the IP your router gets given via ND (Neighbor Discovery) which is different that the Prefix that you get and that never changes (sneaky yes).

So you can use that along with IPv6 NAT (yes I know) setup an internal Static IPv6 Address Prefix and also on your servers and NAT the routers IPv6 Address to the Servers Internal Static IP and it works.

So once I finish our internal Lan (moving everything to fibre cables) to futureproof everything.

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Paul

Thanks for letting me know! Let's hope they get your CGNAT removed.
I've read other people on reddit saying that they've had a difficult time getting Community Fibre to remove it for them. https://www.reddit.com/r/CommunityFibre/comments/1bj...

I think Community Fibre are making a big mistake to not give users the privilege of CGNAT removal of at least 1Gbps. Before I remember that this CGNAT minimum was for 500Mbps users. Now they made it for 3Gbps users only. I think that is somewhat harsh.

I've not yet signed up to them and sadly the service wasn't yet available in my building when Community Fibre had CGNAT removed for 500Mbps users.

I'm still on BT FTTC and generally happy since I can port forward and not worry about blocked ports. I know most gaming servers are dedicated. But there are a few games like eFootball (PES) and others that are peer-to-peer and do rely on port forwarding. This also includes Games for Windows Live like Fable 3, Shadowrun, etc. Though I don't know if these servers are still running as I haven't been playing them for years.

Port Forwarding is a big deal and I remember when I was with BE UNLIMITED* ISP over 10 years ago before that ISP got rebranded to Sky. Their Thomson router did not allow me to port forward! At least I wasn't on CGNAT and just upgrading to a NETGEAR DGN 2000 router solved my problem.

If Community Fibre was simply a case of buying a third party router, I would've joined without much hesitation. But in this case it appears that even changing their router will not make a difference until they don't remove CGNAT.

If one can confirm that by at least making a special request and it gets removed then I'm happy to take the risk and join them. One idea is to threaten to quit. They have the 60 day satisfaction promise to end contract penalty free. Well, let's face it connection speed and latency is not everything. I'd rather have 80Mbps but port forward than 1Gbps but have my ports blocked! Maybe I'm wrong, I don't know. But I'm not yet sure, which decision is more wise, to sacrifice port forwarding over speed or vice versa.

In reply to a post by ian72:

Or unless they have made a policy decision that they will either provide a public IPv4 address or will provide IPv6 but would not provide both. It is unlikely to be a tech limitation but could be a policy of the company.

This default policy of CGNAT IPv4 with native IPv6 is fairly common in eg France (who were a bit ahead of the UK in IPv6 provision) so no great surprise it's being seen in the UK.

They will also revert you to a publicly visible IPv4 if you hassle support but depending on location may lose IPv6 (but at least you can use a tunnel broker to get around it).

Sorry to bring on old thread up from the dead but mid way through my contract which is due to end this October CF put me back on CGNAT claiming that back in March I had renewed my contract with them!

I know prices went up in April, again no email about this increase and the first I knew about it was when I looked at my monthly bill.

Have logged ticket on the CGNAT and price increase but reading between the lines it sounds like their stance may well be tough and the only way to get taken off CGNAT would be to move to their higher speed packages which I don’t need or want.

Can they just make changes like this mid contract as I definitely didn’t “renew” as they claim. I have responded to their last emails but am a bit worried at this point.

To add insult to injury I thought I could make use of IPv6 to use that to get around CGNAT but no matter what I add to the Linksys I can’t connect from outside so am totally not sure what is going on.

I thought I was getting away from Virgins bad CS but having to wait days before they reply with nonsense is just infuriating!

In reply to a post by PaulKirby:

I am with CF and also using a MikroTik (Model number in my sig) and I can confirm that I have both a Public IPv4 and IPv6 and they both work great with Port Forwarding.

Me too. They gave me an IPv4 without me asking for it and only on the cheap 1gbps tier. Seems to me they give a proper IPv4 if they detect you using your own router, which is rather nice of them, even if it is a seemingly unofficial policy.

In reply to a post by candlerb:

But it could be to do with how their network is (badly) designed. Maybe they have one part of the network which has a pool of IPv4 addresses but no IPv6; and they have another part of the network with CGNAT and IPv6. Then they tunnel your session to one or the other.

TBH, CF's network seems pretty vanilla and transparent. I have access to another CF connection that is CGNAT'd and uses their 'Premium Wifi' which is to say Linksys mesh WiFi, so will test a few things...

1) MTU is full 1500, MSS 1460.
2) traceroute confirms an RFC6890 (100.64.0.0/10) IP address, reserved for CGNAT and public IP address (for my session) was in the 95.214.228.0/22 range.
3) I ran a flent test, which predictably was a mess, so no QoS or any evidence respecting priority or dscp (although no ISP would tbh)
4) IPv6 fully provisioned via RA in this IPv6 range.
5) CheckMyNAT.com tells me it's "Port Restricted Cone" (netmap / NAT Type 3), which is pretty typical for CGNAT. Choice of which NAT they use is heavily dependent on which BNG/Access Routers they use. For example, with Mikrotik, it's best practice to use EIM-NAT (Type 1) for UDP traffic, Hairpin NAT for CGNAT P2P traffic (helps things like XBox) and netmap (Type 3) for all other traffic to keep load low.

So this tells me it's pretty standard and follows pretty much all RFC best practice, which is to say, significantly better than the worst ISPs (*ahem* Vodafone IPv6)...

Let me know if you want me to test anything else in particular, both under CGNAT or not.

In reply to a post by candlerb:

Adding IPv6 to the part of the network with IPv4 addresses should be relatively straightforward, but if they've chosen not to do this, then you're stuck.

By default, they are fully dual stack, even on their own routers. IP addresses are MAC-specific (they will still issue to new MAC's, but if you spoof their router MAC, you'll get the same IP as was given to their router).

They issue both an address in the /64 range and a /56 prefix. Again best practice.

Edited by zzing123 (Sun 18-May-25 23:12:44)

In reply to a post by iluvnips:

I know prices went up in April, again no email about this increase and the first I knew about it was when I looked at my monthly bill.

They shouldn't renew the contract if you've asked to leave or terminate the connection. But their T&C's do say they will increase mid-contract every April.

In reply to a post by iluvnips:

Have logged ticket on the CGNAT and price increase but reading between the lines it sounds like their stance may well be tough and the only way to get taken off CGNAT would be to move to their higher speed packages which I don’t need or want.

Maybe use your own router? Both PaulKirby and I have been issued a proper IPv4 on our Mikrotik's. In my case I didn't even ask for it, and I'm on the bog standard 1gbps tariff.

In reply to a post by iluvnips:

To add insult to injury I thought I could make use of IPv6 to use that to get around CGNAT but no matter what I add to the Linksys I can’t connect from outside so am totally not sure what is going on.

The Linksys routers are pretty locked down tbh, and it's probably a result of that rather than a technical issue with the service. But as I said, nothing stopping you using your own router. For the record, I run several permanent Wireguard tunnels to various destinations, and they've never gone down.

Interesting to read about this - I've just started with Connect Fibre who seem to have the same approach. IPv6 all the way, and no port forwarding. TBH, they do say on their website that port forwarding won't work, but it's not easy to find and they don't offer an alternative unless you pay an extra £5 pm for a static IPv4 address.

I've been trying to get around it by using firewall rules but it's made no difference. I never realised just how ugly and complex IPv6 is (well, to me at least).

EDIT - I do seem to have an external IPv6 AND IPv4 address, so still confused as to why port forwarding doesn't work.

Edited by coldnebraskablue (Mon 19-May-25 15:15:14)

In reply to a post by zzing123:

In reply to a post by PaulKirby:

I am with CF and also using a MikroTik (Model number in my sig) and I can confirm that I have both a Public IPv4 and IPv6 and they both work great with Port Forwarding.

Me too. They gave me an IPv4 without me asking for it and only on the cheap 1gbps tier. Seems to me they give a proper IPv4 if they detect you using your own router, which is rather nice of them, even if it is a seemingly unofficial policy.

When I joined them 1Gbit was the fastest they provided. But I explained over the phone what I wanted and said I didn't want to be put on CGNAT due to I run Services here so I need to be able to have incoming connections. I also said that I didn't want to get stuck with a provider if I have issues just after the cooling off period, I was given a free get out clause month and was given a Public IPv4 & IPv6 at a slightly lower price than was advertised.

Also every time I renewed I renewed for 24 Months to get the better price deal. I always make sure they don't put me on CGNAT and explain why and I have always had lovely people the other end explain to me that when I renew its like for like renewal and that the only thing that has changed is the deal price.

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Paul