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UPD ISPs React to the Dangers of Adopting IPv4 Internet Address Sharing

Tuesday, January 22nd, 2013 (9:15 am) - Score 10,669

Perhaps unsurprisingly most of the bigger ISPs weren’t too keen to get into the nitty gritty of CGNAT, with EE (Orange UK) preferring not to comment at all and TalkTalk simply advising us that they had “no plans to introduce Carrier Grade NAT at this time” (this doesn’t mean they won’t do it in the future).

Meanwhile Virgin Media suggested that it was too early to comment and simply re-issued their old statement concerning IPv4 and IPv6 support.

A Virgin Media Spokesperson told ISPreview.co.uk:

As part of our progress towards rolling out IPv6, we have upgraded our network to support IPv6 traffic and we’re currently assessing what changes may need to be made to fully support IPv6 in the home. In the meantime, we have enough IPv4 addresses in reserve to satisfy demand for the foreseeable future and we will be supporting IPv4/IPv6 in parallel until a full IPv6 service is complete.”

Elsewhere Sky Broadband (BSkyB) expects all ISPs to eventually adopt CGN in the future but, due to the technologies inherent problems, they similarly predict that the solution will remain in trial for some time across the industry. Sky also claims to have taken precautions to make sure they don’t run out of IPv4 addresses before websites catch up with their future IPv6 network.

A Sky Broadband Spokesperson added:

It’s likely that a large number of broadband providers will move to CGN in the future. However, due to the potential impact on certain types of online services, we expect it to be extensively tested by the industry first.”

Thankfully the other ISPs, at least those that were willing to comment, were kind enough to dig a little deeper into the issue.

An ISPA UK Spokesperson said:

The transition to IPv6 is on-going and for different ISPs the speed and method of transition varies. Whilst a number of smaller ISPs have already moved to providing native IPv6, others are facing a more complicated transition process which is likely to require the adoption of CGNAT in the medium term whilst true transition solutions are designed. Public trials should be applauded for its openness with their customers, even if there are other transition solutions that would lead to a quicker IPv6 based Internet.”

Piers Daniell, MD of Business ISP Fluidata, said:

This technology has been in use for many years by the mobile operators to provide internet access to millions of handsets. We have been interested in its potential deployment within traditional fixed line ISPs as it does solve the issue that IPv6 isn’t being adopted as quickly as the industry had hoped. Unfortunately widely available IPv6 routers for consumers just don’t exist in the same way that they do with IPv4 so the use of CGN (Carrier Grade NAT) looks like the only viable option going forward. Services such as browsing, email, login to HTTPs sites, VPN and remote desktops should be fine using this solution as they rely on the consumer requesting information from behind their router.

The issues with this solution are for businesses who typically need traffic to start from outside the network and dial into them too. Email servers, VPN endpoints and websites are good examples of traffic that need a fixed public internet address. You can sometimes get around this using DNS hostnames with port mapping but it is not going to fit everyone’s requirements. Therefore we have been taking steps to ensure our IPs last as long as possible so our customers can still conduct their business in the usual manner. Old IPs are being recycled and older larger subnets are not being awarded without strict justifications. We also have the luxury of dual stacking both IPv6 and IPv4 addresses as customers on the whole have more expensive enterprise grade hardware which supports both.”

Adrian Kennard, Director of ISP Andrews & Arnold (AAISP), added:

We are not surprised that some ISPs are having to consider carrier gradeNAT, but we are surprised that ISPs have left it so long to properly implement IPv6 which is the real long term solution here.

Carrier grade NAT adds a new layer of problems and just compounds the difficulties faced by anyone making new services and innovations on the Internet. We already see applications jumping through hoops to work with NAT on customer routers – many of which will not work with carrier grade NAT. Ultimately end users will see a poorer service with more things “not quite working” and more chances for things to break.

All ISPs should be providing proper IPv6 first, and using NAT purely as a stop-gap. This will allow innovation to continue and use the end to end design of IP, and it will mean services using IPv6 will “just work”.

At AAISP we have been providing IPv6 for over 10 years now, and we expect to be able to provide at the very least a single fixed IPv4 address per line without carrier grade NAT for many years to come.”

Steve Lalonde, CTO of Entanet, said:

For those ISPs that don’t have a good supply of IPv4 addresses, Carrier Grade NAT is an inevitable direction until they provide IPv6 and its adoption is properly facilitated by CPE manufacturers. Gladly, we’re not yet in that position and have also been providing IPv6 as an option to all customers for several years. As some of our colleagues here have highlighted, CGN will adversely impact some customers depending on their use of their connections.”


If you believe some of the big ISP spin then the majority of basic internet users won’t have a problem, which is probably true. But CGN still means that anybody wanting to harness the full flexibility of the online world could eventually find their access being stifled by a new layer of network management.

A sizeable portion of broadband consumers in the UK are still likely to be affected, especially those that enjoy modern multiplayer games (there are a lot of gamers around) or hosting their own servers (when not prohibited by an ISPs terms). Some services will of course be able to adapt and not all CGNAT implementations are quite so damaging, yet the only real long-term solution remains full IPv6 adoption.

ISPreview.co.uk has seen good indications that some ISPs may skirt around this issue by offering non-CGNAT packages as an optional upgrade. We think a FREE, not PAID, upgrade solution would be a good way to ensure that those who really need a proper connection can get one, while also preserving the ISPs remaining pool of unique IPv4’s for a lot longer.

In any case it will probably take a few more years before this issue comes back to haunt the industry but haunt it will.

UPDATE 23rd January 2013

Added a comment from Entanet above.

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By Mark Jackson
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 Twitter, , Facebook and Linkedin.
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13 Responses
  1. Andrew Bower says:

    The real disappointment is not that they are trialling CGNAT, but that progress has been so terribly slow at making IPv6 available to subscribers. All the major ISPs are guilty, often in the face of predictions, e.g. of rolling it out by 2012. A little more transparency with their plans would be nice. The current excuse is lack of CPE but there is some capable CPE out there – at least the lack of devices would help them to be able to introduce an IPv6-by-default feature gradually as customers get new routers, saving them from the flag day they fear.

  2. zemadeiran says:

    It’s not only a case of customer CPE’s supporting ipv6.

    Datacenters, servers, and sites all have to shift towards ipv4/ipv6 support.

    We are talking about everyone in the world shifting to ipv6 which incidentally does not need NAT.

    1. Andrew Bower says:

      zemadeiran, the point is that CPE support is one of the ISP excuses and it is a poor one. They mostly claim to have made good progress on their infrastructure already. They do not need to wait for anyone else before starting to put subscribers onto IPv6: it really is a case of “just do it!”

  3. Stuart says:

    I am a host and already offer IPv4 and IPv6, where as we charge for IPv4 addresses we do not charge for IPv6 so getting the addresses out to our client’s is not the issue the problem has to do with the likes of cpanel/plesk not yet supporting IPv6 even through its been mentioned many times as being around the corner I have seen very few sites running of IPv6 the hardware in terms of server/routers can already do this, in most cases it is down to the software used not being ready.

  4. Mark Jones says:

    I suspect the majority of problems with IPV4 shortage is the number of network engineers who still thinks in terms of Class A, B and C subnet masks instead of CIDR. The numbers of wasted /24’s I have seen allocated just for actually using just 30 or so IP addresses is unbelievable. I suspect that if Plusnet have employed somebody to do an audit of their address space armed with a decent IPAM instead of a spreadsheet, a spare /16 or two will have been recovered.

    1. zemadeiran says:

      Good point,

      Also a while back in the news was the DSS’s 16 million ip’s doing nothing…

      Surely ripe can do something???

  5. Olivier says:

    I guess the market will decide between those ISPs with v6 and those with CGN.
    The IPv6 CPE shortage was true a few years ago but we are starting to see many low cost IPv6 compatible CPEs enter the market. Plus most new mobile phones are IPv6 compatible. To implement CGN would be a serious strategic error indeed.

  6. Mark Jones says:

    One of the problem for ISP’s is replacing legacy CPE’s. The bean counters will yell “NO” or “DELAY” to replacing over a million CPE’s at a wholesale cost of approx £15 – £20 a router plus additional delivery and support costs…

    I’m surprised that PlusNet didnt trial ipv6-nat-pt?

    1. Andrew Bower says:

      Why would they have to do that all at once? And that’s just the ones that supply CPE. Even just making service available for customers who ask or providing with new CPE for new customers or when replacing broken equipment would be a very welcome improvement on the current situation of ‘we won’t tell you what we are doing when and anyway we are fine because we have lots of legacy addresses left’

      I agree NAT64/DNS64 would be a good trial to run with native IPv6.

  7. Neil McRae says:

    CPE is still a real issue. Even the ones that do support V6 are very poor.

    But the issue isn’t the access network – the issue is all the services that are IPV4 only, which is the VAST MAJORITY! Of course Alex is going to say everyone should have an IP address – thats what the RIPE NCCs core business is! but the reality is that most users use NAT already and it works perfectly well, its also reduces security issues for those users.

    At some point in time every ISP will have to deploy CG-NAT. IPV4 is going to be around for another ten years at least, people still play Xbox games and PS2 games online!

    Even the latest Nintendo console Wii-U doesn’t support IPV6 and it was launched last month!

    You see Adrian’s comment about offering IPV6 for ten years, there are loads of ISPs that have done this but nobody is queuing at the door for it – why – because most of the apps are still on IPV4.

    Not being able to offer an IPV4 service to new customers would be a strategic error, and even whilst phones support it, tons of apps on the phones don’t support V6!


  8. I am finding more and more IPS are reluctant to provide dedicated IPs, even when your plan is supposed to include them. Recently I was told that needing an IP address for a custom A record was not a valid reason to have one. Is this the future?

  9. cyclope says:

    Isp’s don’t have to supply a router to their customers,and i for one won’t use the bricks they supply as they are usually cheap / poor quality They only provide a router because it saves having trained staff on their tech support,Not that being able to give support to most 3rd party routers would be a difficult task,

    What i have never understood fully is why they all don’t provide all customers with their own static ip, like the smaller and business grade isp’s do, My current router supports IPv6 on another note i personally can’t see many isp’s running out of IPv4 addresses any time soon, as customers leave isp’s as well as join them,so their old IP’s can be re used,

  10. cyclope says:

    Bt retail are rolling out a CGN piot and customers have to opt out if they don’t wan’t CGN, The whole thing about CGN to me is a sign that the big isp’s only care about profits and are treating customers like sheep ,

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