[Fiveplus]

The collapse in IPv4 transfer prices is what caught my eye here, dropping from a ~$55 peak in 2021 to a mean of $22 in early 2026 (figure 12).

This validates my hypothesis that the run-up in 2020–2022 was an artificial scarcity bubble driven largely by hyperscalers. AWS was right up there stockpiling before they shifted their pricing model. Once AWS introduced the hourly charge for public IPv4 addresses (effectively passing the scarcity cost to the consumer), their acquisition pressure vanished. The text notes Amazon stopped announcing almost 15M addresses in Nov 2025. I think they have moved from aggressive accumulation to inventory management.

We are seeing asset stranding in real-time. The market has realized that between the AWS tax and the efficacy of mobile CGNAT, the desperate thirst for public v4 space was not infinite. I'm curious to hear more takes on this.

[JulianHart]

The CGNAT point is underrated. Carriers have zero incentive to move away from it - thousands of users per public IP, no transition cost.

The interesting downstream effect is on IP reputation systems. Traditional detection assumed 1 IP = 1 user. CGNAT breaks that entirely - platforms can't aggressively filter mobile carrier IPs without blocking legitimate customers by the thousands.

Makes sense the IPv4 price dropped once mobile networks proved you can serve massive user bases with relatively few public addresses.

[patmorgan23]

Expect CG-NAT boxes are expensive, and introduce another point of failure into the network. Most mobile carriers are running IPv6 first networks these days anyway.

Like you said, CG-NAT does have the benefit of making v4 address reputation less reliable, which means it's not as big a deal for the transition to v6.

[wcfields]

Anecdotally on how this affects the day to day user experience: I just deployed T-Mobile 5G Business Internet to a temporary pop-up art space (it's only active for a few months) and I'd say twice daily I get a CAPTCHA challenge on Google search.

[SchemaLoad]

I wonder if all these new tools that punch through CGNAT like tailscale will end up breaking it when they force these NAT boxes to maintain tons of long lived connections.

With the uptake in smart home and internet connected CCTV by consumers, things could dramatically shift.

[anyfoo]

I personally hate CGNAT, but I cannot deny that nowadays, the overwhelmingly vast majority of customers most likely does not care (and much less know) that they are behind CGNAT, so this is valid.

Come to think of it, for my use cases, I would probably be fine to be behind IPv4 NAT as long as I also have an un-NATted IPv6 prefix. But a big part of the question here of course is whether IPv6 adoption is worthwhile...

[zokier]

It is noteworthy that in 2020 AWS had very limited ipv6 support, but these days they have at least some support in the most critical services.

[WorldMaker]

> efficacy of mobile CGNAT

At driving the majority of mobile traffic to IPv6? Otherwise, it seems hard to describe mobile CGNAT as efficacious to me.

[inemesitaffia]

Amazon LEO

Aka Kuiper

>stopped announcing almost 15M addresses in Nov 2025

[dlcarrier]

As someone with a background in electronics who doesn't manage any internet-connected equipment but has multiple embedded devices connected to a WAN, I'm glad that IPv4 still seems to have a bit of life left in it.

When IPv6 was developed, over 30 years ago, connecting everything to the internet seemed like a great idea. I know that IPv6 can be made secure, but I don't have the background or research time to learn how to do so, and the NAT-by-default of IPv4 effectively means that I get the benefit of a default-deny security strategy that makes it impossible to accidentally directly connect anything to the internet.

I'm hoping I can keep using IPv4 until IPv8 or IPv4.5 or whatever comes next is developed with the modern proliferation of cheap insecure IoT in mind.

For some background on why IoT products are so insecure:

Hardware manufacturers don't really comprehend the idea of updates, let alone timely of security patches. Hardware has to work on the day of release, so everything is documented and tested to verify it will work. I have hardware with a TCP/IP stack that was released 20 years, (https://docs.wiznet.io/Product/Chip/Ethernet/W5500) and doesn't have a single errata published, despite widespread use. This is expected for every single component, for even the smallest 1-cent transistor, which has dozens of guaranteed performance characteristics laid out over several pages of documentation (https://en.mot-mos.com/vancheerfile/files/pdf/MOT2302B2.pdf).

When manufacturers venture into a product that runs software, they don't realize that for a given complexity, working through undocumented or, worse yet, incorrectly documented APIs takes more time than the equivalent hardware development and documentation. I've worked on multiple projects where software bugs were fixed with hardware workarounds, because it's faster, cheaper, and easier to develop, test, document, retool, and add a few cents of bill-of-materials cost per product, than to get reliable output from the already-written library that's supposed to provide the functionality.

The hardware TCP/IP stack that I linked to was developed at a time when it was the cheapest way to connect a low-power embedded system to a network. Modern low-power embedded systems have multiple cores running at hundreds to thousands of MIPS making the resources to run a softtware TCP/IP stack trivial, but the product still sells well, because when security is an absolute must, the hardware development and maintenance cost for the functionality is still cheaper than through software, even when there's no marginal cost to run the software.

[johnmaguire]

> the NAT-by-default of IPv4

IPv4 is not NAT-by-default. The reality of the world we live in today is that most home networks have a NAT, because you need multiple devices behind a single IP.

That said, I agree: it's quite unknowable how many services I've turned on on local machines with the expectation that a router firewall sat between me and potential clients.

But that doesn't go away with IPv6 - the NAT does, the router doesn't, and the firewall shouldn't either. For example, the default UniFi firewall rules for IPv6 are: 1. Allow Established/Related Traffic (outbound return traffic), 2. Block Invalid Traffic, 3. Block All Other Traffic

You must explicitly open a firewall rule for inbound IPv6 traffic. NAT is not the firewall.

[simoncion]

> I know that IPv6 can be made secure, but I don't have the background or research time to learn how to do so, and the NAT-by-default of IPv4 effectively means that I get the benefit of a default-deny security strategy that makes it impossible to accidentally directly connect anything to the internet.

To get the "unsolicted traffic is rejected or dropped" behavior of the typical IPv4 NAT, forward inbound traffic that's related to an established connection and drop or reject the rest.

You can also use the exact same NAT techniques you use for IPv4 addresses with IPv6 addresses. The only differences are that instead of you using RFC 1918 Private Internets addresses (10./8 and friends) you use RFC 4193 ULA addresses (fd00::/8), and you need the usual NAT rules on your edge router, except for IPv6, rather than IPv4. Remember that IPv6 is still IP, just with larger addresses.

It's recommended that you generate your ULA subnet rather than selecting one by hand, but absolutely nothing stops you from choosing fd::/64. If you're statically assigning addresses to your LAN hosts, then your router could be -say- fd::1 and you count up from there. Also note that DHCP exists for IPv6 [0] and is used by every non-toy OS out there except for Android.

> I'm hoping I can keep using IPv4 until IPv8 or IPv4.5 or whatever comes next...

IPvnext is not happening in either of our lifetimes. You're either going to have to buy edge gear that's set up with a "reject or drop unsolicited inbound forwarding traffic" firewall, or learn how to set it up yourself. Either path is not hard. Well, I guess there's secret option #3: "Die without doing either.". That's also not hard.

[0] It has been around for nearly twenty-three years.

[ianburrell]

IPv6 is just as secure as IPv4. NAT usually combines address translation with a stateful firewall. I remember when they were separate things. IPv6 has the stateful firewall, all the same security but without the mess of address translation.

Also, if you have devices connected to WAN, then they are insecure because they are not NATed.

[huslage]

NAT is not a security measure at all. It just obscures what's behind a firewall, but that is leaky and not reliable from a security perspective. It might make you feel better, but that is not security.

[immibis]

For some background why IoT products will stop being insecure: if you sell one in the EU, you're liable for all the damage your botnet causes.

Luckily, common EU home routers have firewalls, even for IPv6. And it's so much easier to punch holes on purpose! Instead of messing with port forwarding and internal and external IP addresses, you can just say "this device is a server, please allow traffic on port 80 and 443, thank you"

[newsoftheday]

When AWS rolled out plans to start charging for IPv4 addresses:

https://aws.amazon.com/blogs/aws/new-aws-public-ipv4-address...

"As you may know, IPv4 addresses are an increasingly scarce resource and the cost to acquire a single public IPv4 address has risen more than 300% over the past 5 years. This change reflects our own costs and is also intended to encourage you to be a bit more frugal with your use of public IPv4 addresses and to think about accelerating your adoption of IPv6 as a modernization and conservation measure."

Their move disgusted me and I moved from AWS to OCI.

[knollimar]

What disgusted you about it? I'm out of the loop