IPv6 only with IPv4 CGNAT describes most of the large mobile network providers at least in the US.
On Jun 19, 2025, at 6:05 PM, Forrest Christian (List Account) via NANOG <nanog@lists.nanog.org> wrote:
Just to provide some perspective from my viewpoint:
I can run dual-stack. But I don't want to, at least for a specific customer. I want a particular customer to be IPv4 or IPv6, with an eventual transition to 100% IPv6.
I don't want to restart the recurring argument, but I'll just put this out there: Why bother adding the cost of supporting a dual-stack network when there is precisely zero cost for me to stick with IPv4? From a cost perspective, if I have to assign everyone an IPv4 address and an IPv6 address to deploy IPv6, why would I bother assigning the IPv6 address? I have plenty of addresses to continue handing out IPv4 addresses directly to customers for at least several years, so there is no benefit to me in adding the overhead of dealing with both IPv6 and IPv4 on a per-customer basis simultaneously.
However, I'm willing to migrate (over several years) to an IPv6-only network and run a CGNAT box to access IPv4, but only once the cost of running the CGNAT box becomes negligible. Once that occurs, I want to start getting ahead of the curve and set up a CGNAT box, then begin offering only IPv6 to new customers.
Of course, the size and cost of the CGNAT device are directly related to the flows and/or bandwidth, which is why I was curious about the percentages. If it's 10% IPv6, then I'm not close to where I need to be. If it's 95%, then I can (and should) start moving to IPv6. Somewhere in the middle is the threshold, not quite sure where that number is.
On Thu, Jun 19, 2025 at 3:24 PM Mark Andrews via NANOG < nanog@lists.nanog.org> wrote:
You are asking the wrong question.
Switching on IPv6 doesn’t require you to switch off IPv4. You can but you don’t have to. I find it sad that ISPs still think IPv4 and IPv6 are mutually exclusive. Nobody is asking for people to switch off IPv4. They are only asking that you enable IPv6 so they can reach you without having to run the traffic though a CGN 44 or 64.
For most eyeball networks the majority of your traffic will be IPv6 the moment you turn IPv6 on as most of the large content providers offer IPv6 and implementations prefer IPv6.
Mark -- Mark Andrews
On 20 Jun 2025, at 06:13, Forrest Christian (List Account) via NANOG < nanog@lists.nanog.org> wrote:
I see numerous statistics from Google and similar sources that indicate the percentage of end users who are IPv6 native. What I'm missing are statistics going the other way - what percentage of sites (or endpoints that customers regularly connect to) are IPv6-native, from a total traffic perspective?
That is, if I switch to IPv6 on my eyeball network, how much of my existing traffic will I have to CGNAT in some way to reach the IPv4-only network?
We have sufficient IPv4 address resources to stick with IPv4 for the foreseeable future. However, at some point, the percentage of traffic using IPv6 becomes so high that the reasons not to move become less significant. For example, the CGNAT box becomes significantly smaller, as most of the traffic should flow around it on IPv6.
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