New broadband user - MAP-T concerns

[Anonymous]

Good evening all,

I am currently with virgin media (gig1), running my own router/ network/ wi-fi. We had opensense FTTP made available down my street approx. 10 months ago, but have been hanging on until my VM contract is (nearly) up. 

I have ordered sky gigafast FTTP on opensense - 900/100.

I chose sky mainly for a few reasons:

From what I can tell, they use IPoE, rather than PPPoE which I prefer

They have IPV6 (VM STILL doesn't!)

I have read they don't use CGNAT

My go live date is set for 29/09/2025.

I have read a few posts, etc. mentioning MAP-T. I am concerned as I run my own VPN server and also VPN for work so need a proper IPv4 address. I'm not worried about a dynamic address as I use dynamic DNS.

Am I likely to get a MAP-T address? And if so, can I opt-out?

Also, is the guide for OPNSense still relevant (I.e. DHCP option 61)?

Thanks so much in advance!

[GD1]

@Anonymous  I think you mean Openreach when referring to the network operator?

[Anonymous]

Yes! Good spot, thanks

[Chrisee]

@Anonymous to explain Sky only use MAP-T if the router advertises support (i think this is requires DHCPv6 Option95)  which the Sky Max hub does so if you use your own router this should not be an issue. Sky are likely to supply a Sky Max hub if they do and you decide to use that then you can enable UPnP which changes the sharing ratio from 8:1 to 1:1 or you can ask Sky for an opt out which they will do if there is a legitimate reason for your request see the pinned post at the top of the forum

Sky fully support IP6 but offer a full dual stack so you will have a public IP4 address which while "dynamic" only changes rarely unless you reboot the router. The Sky Max hub does not support DNS.

There are two possible ways a router can authenticate  a Sky connection the first is DHCPv4 Option 61 with a standard string in the form 

anything@skydsl|anything. not every router manufacturer offers this option for example TP-Link doesnt
The second method in DHCPv6 PD which more routers support but only 80% of Openreach exchanges support so there is a risk your's might not. However 100% of City Fibre connections do provide support should Sky use their network.

[Anonymous]

Hi @Chrisee - good to speak to you, I have seen quite a few posts by yourself, but wanted to check where the land lay as of now as MAP-T or CGNAT would be a deal breaker for me and I would cancel my order if I couldn't opt out.

So yes, just to be clear (I was typing on my phone last night):

My connection will be through Opensense (no cityfibre where I am).

I will not be using the Sky Max Hub - I am running OPNSense on dedicated hardware as a router, and will be directly from the ONT - and can definately authenticate with DHCPv4 Option 61 if that will prevent me from getting a MAP-T address. I won't be authenticating with DHCPv6 PD.

I already use 1.1.1.1 as my DNS, which I believe supports IPv6.

Do you see any issues with the above please?

Will I still get IPv6 connectivity without authenticating through DHCPv6 PD?

Thank you!

[Chrisee · Accepted solution]

@Anonymous that should work assuming your router does not advertise support for DHCPv6 Option 95. There was an issue with Ubquiti kit which advertised the option but in practice could not support it caused endless issues. After something like 8 years Ubiquiti finally fixed this last year in a firmware update IIRC. 

The Option 61 method works on all UK Sky lines.

Keep the Sky hub available as Sky will require that to be in place if you report line issues. Sky offer no support to anything other than their own kit but this forum is a useful place to ask. Howevervthey are agnostic