FullFibre Limited Solves IPv4 Shortage With netElastic BNG And CGNAT
Alternative UK broadband operator FullFibre Limited, which in 2023 acquired rival Digital Infrastructure (BeFibre) and in 2025 completed its merger with Zzoomm (here), has now apparently solved its “IPv4 shortage” (internet addresses) with netElastic’s software and will be returning excess IPv4 blocks with the use of CGNAT (IP address sharing) being projected to save 40% over 3 years.
Just to recap. The combined gigabit speed Fibre-to-the-Premises (FTTP) broadband network currently reaches 600,000 UK premises (ready for service) and “over” 90,000 customers (up from 80k in July 2025) across England – serving parts of approximately 110 market towns, which makes it one of the country’s largest altnets. This reflects both their open access wholesale fibre network alongside their in-house retail ISP(s).
However, the effort to slowly combine three networks (FullFibre, Digital Infrastructure and Zzoomm) into a single entity, including the associated retail ISPs, did create some challenges. According to netElastic, this left the provider “battling limitations from their previous vendor regarding costly and time-consuming IP address acquisition“, while also needing to scale its capacity to serve over 140,000 subscribers.
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For example, while evaluating upgrade solutions, FullFibre is said to have discovered that Juniper MX routers did not combine Broadband Network Gateway (BNG) and Carrier Grade Network Address Translation (CGNAT) while taking up two rack units each. But netElastic were able to offer a single box, one rack unit solution for BNG, CGNAT and netVision monitoring application.
Running on standard x86 Dell XR servers with Intel Xeon Gold and 100G NICs, the networking software platform delivers routing, subscriber management and CGNAT with centralized GUI-based management. Returning excess IPv4 blocks with CGNAT is also projected to save 40% over three years, while halving rack space and power draw. FullFibre also discovered it could move DHCP onto the router itself. Lease times dropped from one hour to five minutes, allowing the network to detect and renegotiate lost connectivity much faster.
Dave Bell, Head of Networks for FullFibre, said:
“If you’re planning any major broadband network upgrade or consolidation, don’t default to traditional hardware BNGs. Look seriously at software-based platforms like netElastic’s — they give you the flexibility, massive cost savings, and the future-proofing you actually need in today’s IPv4-scarce, high-growth environment.”
Weixiao Liu, CEO of netElastic, said:
“We’re proud to support FullFibre’s ambitious growth journey with our integrated BNG and CGNAT solution. FullFibre’s success shows exactly why service providers worldwide are moving to software networking: lower TCO, faster scaling, and the freedom to focus resources on customers instead of expensive legacy hardware.”
Admittedly the greater use of IP address sharing (CGNAT) isn’t usually much of a positive selling point for the more technically minded pool of retail consumers, although full support for IPv6 often helps to mitigate some of the negatives. The good news is that FullFibre’s network is said to fully support IPv6 and likely runs most traffic on native IPv6. Similarly, their primary in-house ISP, which is now Zzoomm, has also long been known to support IPv6.
A bunch of YouTube videos on all this can be found here, although for some reason they’ve split one video up into several separate pieces, which is a bit unusual. Otherwise, there’s also a related case study document (PDF), which adds a little bit more background on the change.
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Mark is a professional technology writer, IT consultant and computer engineer from Dorset (England), he also founded ISPreview in 1999 and enjoys analysing the latest telecoms and broadband developments. Find me on X (Twitter), Mastodon, Facebook, BlueSky, Threads.net and Linkedin.
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I would wonder how well this scales.
Maybe FF have such a low density of customers that a server or two per headend can handle it all, but the major ISPs might have tens of thousands of customers at a single Openreach handover point and their kit will be doing more than just broadband termination.
“legacy” hardware (especially with the custom ASICs) remains king. (I would like to state my absolute hatred of the tech industry practice of branding everything they chose not to do as “legacy”, as if it is a bad thing)
The obsession with network function virtualisation has been going on for years, and there was a time that you couldn’t go a day without hearing about “white box switches” that can run anyone’s software, or claiming that a server can replace fault-tolerant hardware, but it has yet to materialise in the way they hoped. It seems to have gone the other way with hardware vendors adopting greater programmability and the ability to run containers or VMs.
My guess is that it is simply down to cost. Juniper would be more expensive. It’s not about shaving off a couple U of rack space or a few watts, though would that not be taken up with fan-out switches and other ancillaries that are normally built into the “legacy” hardware?
Legacy: a computer industry term that means “it works”.
CGNAT is a disaster if you have a device that needs to receive unsolicited network traffic such as a SIP based VOIP phone line.
CGNAT is only a disaster on those ISPs which don’t do IPv6 or with any VoIP suppliers who don’t do IPv6 or for users who won’t do IPv6
Yes, like Airband (CGNAT no IPv6). So irritating.
@DFScale, from what I have read and seen over a few months, some game servers don’t support IPv6 and they also don’t like CGNAT.
I can understand why companies are using CGNAT, IPv4 have been running out for years and there been warnings of this for years and yet very little was done. IPv6, confuses the hell out of me, but is the answer and have been available for years.
So all of this should have been sorted years ago.
Even ISPs on the Openreach network are going to have the same problem, if they don’t already.
I knew BTivor would love this article
Adrian. What has Openreach’s network have to do with it?
That’s nonsense.
You seem to forget what their purpose is – they build an access network for communication providers to sell. They don’t sell transit services.
Personally I have no complaints with ISPs using CGNAT these days (as long as they also offer static ip’s to those who need them), newer ISPs missed out on the IPv4 allocation boat and now IPv4 addresses are expensive when the majority of an ISPs customer base can get along just fine behind a CGNAT (all the people on mobile broadband and cell phones getting by just fine).
IP Phones can work behind a nat as long as the software is configured to establish an outgoing connection to the IP Phone provider. I have a real old sipgate account with a couple of numbers attached to it I use for toy projects, and that works fine behind a nat on something like FreePBX if its configured to maintain an outgoing connection to sipgate (even though I have a static IP address, I don’t have ports 5060/5061 pointing to my freepbx instance and it receives calls just fine), though having ports open does offer as another level of fault tolerance and not being CG-NAT’ed saves for any time the CGNAT applance decides to drop the long running open connection.
They must be dealing with very low volumes of traffic if they’re able to do routing on an off-the-shelf x86 server. ASICs are still kings for both efficiency and speed when you’re pushing any kind of reasonable traffic.
You’d be surprised – I’ve deployed this and it’s capable of 100Gbps on the right hardware