3/12/2026 at 6:19:59 PM
> In a nutshell, an IPv4x packet is a normal IPv4 packet, just with 128‑bit addresses. The first 32 bits of both the source and target address sit in their usual place in the header, while the extra 96 bits of each address (the “subspace”) are tucked into the first 24 bytes of the IPv4 body. A flag in the header marks the packet as IPv4x, so routers that understand the extension can read the full address, while routers that don’t simply ignore the extra data and forward it as usual.So you have to ship new code to every 'network element' to support IPv4x. Just like with IPv6.
So you have to update DNS to create new resource record types ("A" is hard-coded to 32-bits) to support the new longer addresses, and have all user-land code start asking for, using, and understanding the new record replies. Just like with IPv6. (And their DNS idea won't work—or won't work differently than IPv6: a lot of legacy code did not have room in data structures for multiple reply types: sure you'd get the "A" but unless you updated the code to get the "AX" address (for ipv4X addresses) you could never get to the longer with address… just like IPv6 needed code updates to recognize AAAA, otherwise you were A-only.)
You need to update socket APIs to hold new data structures for longer addresses so your app can tell the kernel to send packets to the new addresses. Just like with IPv6.
A single residential connection that gets a single IPv4 address also gets to use all the /96 'behind it' with this IPv4x proposal? People complain about the "wastefulness" of /64s now, and this is even more so (to the tune of 32 bits). You'd probably be better served with pushing the new bits to the other end… like…
* https://en.wikipedia.org/wiki/IPv6#IPv4-mapped_IPv6_addresse...
by throw0101d
3/13/2026 at 3:26:55 AM
If you put part of the address in the body space, you can't encrypt the entire body.IPv6 adoption has been linear for the last two decades. Currently, 48% of Google traffic is IPv6.[1] It was 30% in 2020. That's low, because Google is blocked in China. Google sees China as 6% IPv6, but China is really around 77%.
Sometimes it takes a long time to convert infrastructure. Half the Northeast Corridor track is still on 25Hz. There's still some 40Hz power around Niagara Falls. San Francisco got rid of the last PG&E DC service a few years ago. It took from 1948 to 1994 to convert all US freight rail stock to roller bearings.[2] European freight rail is still using couplers obsolete and illegal in the US since 1900. (There's an effort underway to fix this. Hopefully it will go better than Eurocoupler from the 1980s. Passenger rail uses completely different couplers, and doesn't uncouple much.)[3]
[1] https://www.google.com/intl/en/ipv6/statistics.html
[2] https://www.youtube.com/watch?v=R-1EZ6K7bpQ
[2] https://rail-research.europa.eu/european-dac-delivery-progra...
by Animats
3/13/2026 at 1:26:22 PM
should also bring to mind that there's a technological leapfrogging effect in stages of development which it seems clear that China has taken advantage of.by riffic
3/12/2026 at 6:23:24 PM
Yes, I was wondering if I was missing something reading the hypothetical: This is still splits the Internet into two incompatible (but often bridged etc.) subnetworks, one on the v4, one on the v4x side, right?It just so happens that, unlike for v6, v4 and v4x have some "implicit bridges" built-in (i.e. between everything in v4 and everything in v4x that happens to have the last 96 bits unset). Not sure if that actually makes anything better or just kicks the can down the road in an even more messy way.
by lxgr
3/12/2026 at 6:56:42 PM
> everything in v4x that happens to have the last 96 bits unsetThat's pretty much identical to 6in4 and similar proposals.
The Internet really needs a variant of the "So, you have an anti spam proposal" meme that used to be popular. Yes, it kill fresh ideas in the bud sometimes, but it also helps establish a cultural baseline for what is constructive discussion.
Nobody needs to hear about the same old ideas that were subsumed by IPv6 because they required a flag day, delayed address exhaustion only about six months, or exploded routing tables to impossible sizes.
If you have new ideas, let's hear them, but the discussion around v6 has been on constant repeat since before it was finalized and that's not useful to anyone.
by xorcist
3/12/2026 at 7:01:43 PM
I feel like the greatest vindication of v6 is that I’m reading the same old arguments served over a quietly working v6 connection more often than not. While people were busy betting on the non-adoption of v6, it just happened.—Sent from my IPv6 phone
by lxgr
3/15/2026 at 6:51:34 PM
I don’t know if it anyone was really making bets around it… it’s just kind of individually meaningless to implement support for until it’s already popular, because you still have to support IPv4 in full until the day you can remove it entirelyby setr
3/12/2026 at 8:09:07 PM
> The Internet really needs a variant of the "So, you have an anti spam proposal" meme that used to be popular.For those unfamiliar:
by throw0101d
3/13/2026 at 1:41:19 AM
Public reluctance to accept weird new forms of money has turned out to be a myth.by dullcrisp
3/13/2026 at 4:43:06 AM
I don't think that's true.There are a ton of weird coins around, sure, but no-one is using them as money.
I still have to stump up actual dollars backed by a government if I want to buy a coffee.
by marcus_holmes
3/12/2026 at 10:30:07 PM
This wasn't a proposal, but an alternate history. The world where the people who wished for IPv4 but with extra address space get their way. By the end I come down on being happy with we're in the IPv6 world, but wishing interoperability could be slicker.by billpg
3/13/2026 at 12:04:34 PM
> It just so happens that, unlike for v6, v4 and v4x have some "implicit bridges" built-in (i.e. between everything in v4 and everything in v4x that happens to have the last 96 bits unset).See perhaps:
> For any 32-bit global IPv4 address that is assigned to a host, a 48-bit 6to4 IPv6 prefix can be constructed for use by that host (and if applicable the network behind it) by appending the IPv4 address to 2002::/16.
> For example, the global IPv4 address 192.0.2.4 has the corresponding 6to4 prefix 2002:c000:0204::/48. This gives a prefix length of 48 bits, which leaves room for a 16-bit subnet field and 64 bit host addresses within the subnets.
* https://en.wikipedia.org/wiki/6to4
Have an IPv4 address? Congratulations! You get entire IPv6 /48 for free.
by throw0101d
3/13/2026 at 5:40:12 PM
As I recall, 6to4 worked beautifully between 6to4 nodes in the absence of middlebox interference. The fatal flaw was the anycast address for accessing the "real" IPv6 network. The rosy outcome imagined in the article doesn't require a hypothetical IPv4 extension: just the novel idea of leaving the IPv4 core alone and extending the edge - which would have brought the financial incentives into alignment.by perennialmind
3/12/2026 at 7:12:33 PM
I might be interpreting wrong, but doesn't IPv6 also have a "implicit bridge" for IPv4?by joseda-hg
3/12/2026 at 10:31:00 PM
If it does that's great, but why couldn't I connect to IPv6-only services back when my ISP was IPv4 only?by billpg
3/12/2026 at 11:47:44 PM
It's one way, v6 is aware of v4, but not the other way aroundby joseda-hg
3/13/2026 at 1:37:03 AM
It's not automatic, there were many proposed and utilized mechanisms for autodetecting translation servers and so on. By now though, if you want IPv6, you order real IPv6, and don't need some translation.by pocksuppet
3/12/2026 at 6:58:47 PM
IPv6 had an implicit bridge called 6to4 but it was phased out because it wasn't that reliable.by wmf
3/13/2026 at 5:53:46 PM
There was no upside for an ISP to operate a 6to4 relay, so the anycast address was worse than a blackhole route. It would occasionally permit a connection, but mostly just caused timeouts. Without that poison pill, it could have been a nice way to allow for connecting private subnets that otherwise use conflicting RFC1918 subnets. That's what I used it for.by perennialmind
3/14/2026 at 12:10:27 AM
Two 6to4 networks will communicate directly between each other without using a relay, so it will still work for that. Although you ought to be able to use native v6 these days.If you can't deploy v6 (whether native or 6to4) on the remote side for whatever reason, NAT64 is useful for dealing with conflicting RFC1918. You map each instance of RFC1918 you need to access into different v6 /96s, and then they don't conflict from your perspective. (But like NAT44, it only works for outbound connections; inbound ones need a port forward.)
by Dagger2
3/12/2026 at 9:11:55 PM
> Just like with IPv6.Yes, but the compatibility is very very easy to support for both hardware vendors, softwares, sysadmins etc. Some things might need a gentle stroke (mostly just enlarge a single bitfield) but after that everything just works, hardware, software, websites, operators.
A protocol is a social problem, and ipv6 fails exactly there.
by bmacho
3/12/2026 at 9:47:53 PM
What slowed ipv6 wasn’t the design of ipv6, it was the invention of NAT and CGNAT.Even still. The rollout is still progressing, and new systems like Matter are IPv6 only.
by Gigachad
3/12/2026 at 10:20:40 PM
What stymies IPv6 is human laziness more than anything else. It's not hard to set up. Every network I run has been dual stack for 10 years now, with minimal additional effort. People are just too lazy to put forth even a minimal effort when they believe that there's no payoff to it.by bigstrat2003
3/12/2026 at 11:25:33 PM
> What stymies IPv6 is human laziness more than anything else. It's not hard to set up.I think the biggest barrier to IPv6 adoption is that this is just categorically untrue and people keep insisting that it isn't, reducing the chance that I'd make conscious efforts to try to grok it.
I've had dozens of weird network issues in the last few years that have all been solved by simply turning off IPv6. From hosts taking 20 seconds to respond, to things not connecting 40% of the time, DHCP leases not working, devices not able to find the printer on the network, everything simply works better on IPv4, and I don't think it's just me. I don't think these sort of issues should be happening for a protocol that has had 30 years to mature. At a certain point we have to look and wonder if the design itself is just too complicated and contributes to its own failure to thrive, instead of blaming lazy humans.
by akersten
3/15/2026 at 11:29:33 AM
Sage Accounting is prone to various connectivity gollywobbles between the server and workstations. The first troubleshooting recommendation is to turn off IPv6. About 75% of that time, the problem then goes away.by Froedlich
3/15/2026 at 5:04:55 PM
If you disable the NIC, the problem goes away 100% of the time.Don't blame v6 for problems with your network.
by Dagger2
3/13/2026 at 3:31:32 PM
Yes, if you can’t properly setup a network now then IPv6 won’t help you. That isn’t IPv6’s fault.by ectospheno
3/12/2026 at 11:16:22 PM
> People are just too lazy to put forth even a minimal effort when they believe that there's no payoff to it.For me just disabling IPv6 has given the biggest payoff. Life is too short to waste time debugging obscure IPv6 problems that still routinely pop up after over 30 years of development.
Ever since OpenVPN silently routed IPv6 over clearnet I've just disabled it whenever I can.
by jampekka
3/12/2026 at 10:57:53 PM
This goes the other direction too. I just this second fixed a problem with incredibly slow SSH connections because a host lookup which returned an IPv4 address instantly was waiting 10+ seconds for an IPv6 response which would never come.Now I'm sure I can fix DNSmasq to do something sensible here, but the defaults didn't even break - they worked in the most annoying way possible where had I just disabled IPv6 that would've fixed the entire problem right away.
Dual stack has some incredibly stupid defaults.
by XorNot
3/13/2026 at 7:44:04 PM
> Dual stack has some incredibly stupid defaults.Dual stack is the problem, and it's not going away in the next 20 years.
Single stack ipv4, fine, if your applications support it then great.
Single stack ipv6, fine, if your applications support it then great.
Dual stack is just horrendous, you can never be sure what stack you're on when you work at a higher level.
by iso1631
3/13/2026 at 11:53:06 PM
If your DNS server isn't replying to requests, your DNS server is broken. That has nothing to do with v6.by Dagger2
3/14/2026 at 1:13:19 AM
If the problem gets fixed by simply disabling v6, it has much to do with v6.by jampekka
3/15/2026 at 5:15:21 PM
It might get hidden by disabling v6, but not fixed. And if your DNS server fails to reply to an AAAA lookup over v4, that's 100% not a v6 problem.by Dagger2
3/13/2026 at 12:18:39 AM
I'm confused by the argument that replacing equipment is something that is always possible. It doesn't matter that it's easy to support by updating or replacing the hardware - a lot of hardware isn't going to be updated or replaced.by LoganDark
3/13/2026 at 1:42:17 AM
ISPs are used to this though, and tunnel a lot of packets. If you have DSL at home, your ISP doesn't have a router in every edge cabinet - your DSL router sets up a layer-2 point-to-point tunnel to the ISP's nearest BRAS (broadband remote access server) in a central location. All IP routing happens there. Because it's a layer-2 tunnel it looks like your router is directly connected to the BRAS, even though there are many devices in between. I don't know how it's done on CATV and fiber access networks.If an ISP uses an MPLS core, every POP establishes a tunnel to every other POP. IP routing happens only at the source POP as it chooses which pre-established tunnel to use.
If an ISP is very new, it likely has an IPv6-only core, and IPv4 packets are tunneled through it. If an ISP is very old, with an IPv4-only core, it can do the reverse and tunnel IPv6 packets through IPv4. It can even use private addresses for the intermediate nodes as they won't be seen outside the network.
by pocksuppet
3/12/2026 at 10:05:49 PM
No, in this hypothetical, routers that don't know about IPv4x will still route based on the top 32 bits of the address which is still in the same place for IPv4 packets. If your machine on your desk and the other machine across the internet both understand IPv4x, but no other machines in the middle do, you'll still get your packets across.by billpg
3/12/2026 at 10:15:34 PM
Well no, all the routers on your subnet need to understand it.So let’s say your internet provider owns x.x.x.x, it receives a packet directed to you at x.x.x.x.y.y… , forwards it to your network, but your local router has old software and treats all packages to x.x.x.x.* as directed to it. You never receive any medssagea directly to you evem though your computer would recognise IPv4x.
It would be a clusterfuck.
by kolinko
3/12/2026 at 10:38:17 PM
Your local machine isn't on the IPv4 internet if it doesn't have a globally routable IPv4 address.Your home router that sits on the end of a single IPv4 address would need to know about IPv4x, but in this parallel world you'd buy a router that does.
by billpg
3/14/2026 at 12:46:59 AM
Of course you are, just behind NAT.If your device has it's own public IPv4 address then you don't need IPv4x, IPv6 or whatever else.
by kolinko
3/12/2026 at 11:40:11 PM
How would anything on the internet know about x.x.x.x.y.y…?Your computer knows it’s connected to an old router because dhcp gave it x.x.x.x address and not x.x.x.x... so it knows it’s running in old v4 mode.
And it can still send outbound to a v4x address that it knows about.
by digitalPhonix
3/14/2026 at 12:51:16 AM
> And it can still send outbound to a v4x address that it knows about.No, it cannot, if there is a router on the way that is unaware of v4x, it will interrupt the signal.
Say your router is 1.2.3.4.0.0 in IPv4x (and 1.2.3.4 in IPv4). You are 1.2.3.4.0.1 . Someone sends you a message from outside. Your router only sees the previx of the address (1.2.3.4), and since it thinks it has 1.2.3.4, it reads the message and doesn't forward it further.
I highly recommend reading original TCP/IP RFC - it is a good tutotrial on how the IP routing works: https://datatracker.ietf.org/doc/html/rfc1180
by kolinko
3/12/2026 at 9:04:40 PM
The advantage, as i see it, is that this could be done incrementally. Every new router/firmware/os could add support, until support is ubiquitous.Contrast this with ip6, which is a completely new system, and thus has a chicken and egg problem.
by arka2147483647
3/12/2026 at 9:49:51 PM
That is how v6 worked though. Every router and consumer device supports v6 and has for a very long time now. The holdup ended up being ISPs.Today it seems most ISPs support it but have it behind an off by default toggle.
by Gigachad
3/12/2026 at 11:41:42 PM
Wouldn't this proposal not require isps to do anything? They already assign every user a unique ipv4 address. Then, with this proposal, if I want to have a bunch of computers behind that single ipv4 ip, I could do it without relying on NAT tricksby IncreasePosts
3/13/2026 at 12:58:20 AM
> Wouldn't this proposal not require isps to do anything? They already assign every user a unique ipv4 address.The reason there's an IPv4 address shortage is because ISPs assign every user a unique IPv4 address. In this alternative timeline, ISPs would have to give users less-than-an-IPv4 address, which probably means a single IPv4x address if we're being realistic and assuming that ISPs are taking the path of least resistance.
by jcranmer
3/13/2026 at 12:09:20 PM
If that happens then the user can only communicate with hosts supporting IPv4x and you're back to the IPv6 issueby SkiFire13
3/13/2026 at 5:47:14 PM
As long as IPv4x support was just something you got via software update rather than a whole separate configuration you had to set up, the vast majority of servers probably would have supported IPv4x by the time addresses got scarce.However, if it did become a problem, it might be solvable with something like CGNAT.
by comex
3/13/2026 at 8:01:32 PM
CGNAT would also be easier on routers too, since currently they need to maintain a table of their port being used to the destination ip and port. Whereas with ipv4x, the routing information can be determined from the packet itself and no extra memory would be requiredby IncreasePosts
3/13/2026 at 8:32:03 PM
That's only true when forwarding IPv4x -> IPv4. When you're going the reverse direction and you need to forward IPv4 -> IPv4x, well, still need a table then.by jcranmer
3/13/2026 at 12:46:28 AM
There aren’t enough IPv4 addresses to give everyone one. That is why ISPs use CGNAT to hide multiple customers behind one IP address.Something that just uses IPv4 won’t work without making the extra layer visible. That may not have been apparent then but it is now.
by ianburrell
3/13/2026 at 1:20:31 PM
IPv6 is a parallel system. It exists with IPv4. You don't need to stop using IPv4 - ever - if you don't want to. You can have both the chicken and egg together as long as is needed.At some point IPv4 addresses will cost too much.
by RiverCrochet
3/12/2026 at 11:33:07 PM
you are missing the point - updating "network elements" was never the problem. Linux kernel has IPv6 support since 2.6. RedHat got IPv6 in 2008. Nginx got it in 2010. And yet there plenty of IPv4-systems out there. why?Software updates scale _very well_ - once author updates, all users get the latest version. The important part is sysadmin time and config files - _those_ don't scale at all, and someone needs to invest effort in every single system out there.
That's where IPv6 really dropped the ball by having dual-stack the default. In IPv4x, there is no dual-stack.
I upgrade my OS, and suddenly I can use IPv4x addresses... but I don't have to - all my configs are still valid, and if my router is not compatible, all devices still fall back to IPv4-compatible short addresses, but are using IPv4x stack.
I upgrade the home router and suddenly some devices get IPv4x address... but it is all transparent to me - my router's NAT takes care of that if my upstream (ISP) or a client device are not IPv4x-capable.
I have my small office network which is on the mix IPv4 and IPv4x addresses. Most Windows/Linux machines are on IPv4x, but that old network printer and security controller still have IPv4 address (with router translating responses). It still all works together. There is only one firewall rule set, there is only one monitoring tool, etc... My ACL list on NAS server has mix of IPv4 and IPv4x in the same list...
So this is a very stark contrast to IPv6 mess, where you have to bring up a whole parallel network, setup a second router config, set up a separate firewall set, make a second parallel set of addresses, basically setup a whole separate network - just to be able to bring up a single IPv6 device.
(Funny enough, I bet one _could_ accelerate IPv6 deployment a lot by have a standard that _requires_ 6to4/4to6/NAT64 technology in each IPv6 network... but instead the IPv6 supporters went into all-or-nothing approach)
by theamk
3/13/2026 at 12:20:39 AM
"I bet one _could_ accelerate IPv6 deployment a lot by have a standard ..."ahem
by billpg
3/13/2026 at 12:49:53 AM
"The good thing about standards is that there are so many to choose from."by theamk
3/13/2026 at 1:33:10 AM
> Software updates scale _very well_ - once author updates, all users get the latest version. The important part is sysadmin time and config files - _those_ don't scale at all, and someone needs to invest effort in every single system out there.With IPv6 the router needs to send out RAs. That's it. There's no need to do anything else with IPv6. "Automatic configuration of hosts and routers" was a requirement for IPng:
* https://datatracker.ietf.org/doc/html/rfc1726#section-5.8
When I was with my last ISP I turned IPv6 on my Asus router, it got a IPv6 WAN connection, and a prefix delegation from my ISP, and my devices (including by Brother printer) started getting IPv6 addresses. The Asus had a default-deny firewall and so all incoming IPv6 connections were blocked. I had do to zero configuration on any of the devices (laptops, phones, IoT, etc).
> I upgrade my OS, and suddenly I can use IPv4x addresses... but I don't have to - all my configs are still valid, and if my router is not compatible, all devices still fall back to IPv4-compatible short addresses, but are using IPv4x stack.
So if you cannot connect via >32b addresses you fall back to 32b addresses?
* https://en.wikipedia.org/wiki/Happy_Eyeballs
> I upgrade the home router and suddenly some devices get IPv4x address... but it is all transparent to me - my router's NAT takes care of that if my upstream (ISP) or a client device are not IPv4x-capable.
* https://en.wikipedia.org/wiki/IPv6_rapid_deployment
A French ISP deployed this across their network of four million subscribers in five months (2007-11 to 2008-03).
> There is only one firewall rule set, there is only one monitoring tool, etc... My ACL list on NAS server has mix of IPv4 and IPv4x in the same list...
If an (e.g.) public web server has public address (say) 2.3.4.5 to support legacy IPv4-only devices, but also has 2.3.4.5.6.7.8.9 to support IPv4x devices, how can you have only one firewall rule set?
> So this is a very stark contrast to IPv6 mess, where you have to bring up a whole parallel network, setup a second router config, set up a separate firewall set, make a second parallel set of addresses, basically setup a whole separate network - just to be able to bring up a single IPv6 device.
Having 10.11.12.13 on your PC as well as 10.11.12.13.14.15.16 as per IPv4x is "a second parallel set of addresses".
It is running a whole separate network because your system has the address 10.11.12.13 and 10.11.12.13.14.15.16. You are running dual-stack because you support connection from 32-bit-only un-updated, legacy devices and >32b updated devices. This is no different than having 10.11.12.13 and 2001:db8:dead:beef::10:11:12:13.
by throw0101d