I spent a week without IPv4 (2023)

125 pointsposted 11 hours ago
by mahirsaid
(apalrd.net)

219 Comments

jrmg

9 hours ago

I’m surprised home many technically knowledgeable people on Internet forums still think IPv6 is some niche, unreliable thing.

In my direct experience, in the USA, at least Spectrum, AT&T, and Xfinity (Comcast) still run IPv4, of course, but they also have IPv6 working and on by default on their home internet offerings.

All mainstream computer and mobile OSes support it by default and will prefer to connect with it over IPv4.

‘Everyone’ in many areas is using it. For many of us, our parents are using Facebook and watching Netflix over it. Over 50% of Google’s American traffic is over it. It just works.

nine_k

4 hours ago

T-Mobile, a major phone provider, runs an ISP which is IPv6 only. That is, your phone never gets an IPv4, unless connected to WiFi. They offer home access points with a 5G modem and a router; the external address is also IPv6 only.

It works plenty well. I access everything accessible via IPv6, and the rest through their 464XLAT, transparently.

My LAN still has IPv4, because some ancient network printers don't know IPv6. OpenWRT on my router supports IPv6 just fine. Of course I do not expose any of my home devices to the public internet, except via Wireguard.

themafia

an hour ago

Ironically there's T-Mobile Business which is static IPv4 only.

LeoPanthera

9 hours ago

My problem with IPv6 is that my ISP (Xfinity) won't give me a static prefix, so every now and again it changes.

Unlike IPv4, my LAN addresses include the prefix, so every time they change it, all my LAN addresses change.

Combined with the lack of DHCP6 support in many devices, this means reverse DNS lookups from IP to hostname can't be done, making identifying devices by their IP essentially impossible.

db48x

8 hours ago

I think you’re conflating multiple things there. There’s nothing magical about IPv4 that gives your LAN addresses stability when your ISP changes your IP prefix. That’s provided by your router doing network address translation. You send a packet from your address which is 192.168.0.42 (a local address), and your router changes the bytes in the packet so that it comes from X.Y.Z.W (your router’s public address). If you really wanted it to your router could do the same thing for IPv6.

IPv6 also has local addresses, but a lot more of them. Anything starting with fd00::/8 is a local address with 40 bits available as the network number. So you can set up your local network with the prefix fdXX:XXXX:XXXX::/48 (where the Xs are chosen randomly) as the prefix and still have 16 bits left over for different subnets if you want. These addresses do not change when your ISP changes your public prefix.

And if you want to add reverse dns for SLAAC addresses then just have your router listen for ICMPv6 Neighbor Announcement addresses and use them to update your DNS server as appropriate. Or configure your servers to use stable addresses based on their MAC address rather than random addresses (which are better for privacy), and then just configure the DNS as you add and remove servers.

littlecranky67

7 hours ago

what servers?

Dylan16807

6 hours ago

The things on your LAN that you're connecting to via DNS and IP, which cause the desire to have stable LAN IPs in the first place.

shibapuppie

5 hours ago

That's what DNS is for... to not need to remember or know numerical addresses.

Dylan16807

5 hours ago

And DNS is easier to set up if the IP doesn't change constantly.

This conversation is going in circles.

vel0city

an hour ago

If you're doing your DNS properly it's not really that difficult. If you're statically definining all your DNS you're doing it wrong.

Dylan16807

an hour ago

Okay, how do I properly set DNS so it tracks the changing public addresses of my desktop and printer? And I'd better still be able to use SLAAC.

vel0city

an hour ago

You register addresses based on Router/Neighbor Advertisements in NDP. In your RA, you'd point it to your DNS server, which would then handle registration when hosts check in with their new IP addresses.

baq

8 hours ago

you should advertise a local prefix (anything in fd00::/8) in your network and it should just work. no need to use the isp-provided prefix for lan.

hdgvhicv

8 hours ago

My ISP will route as many /64s to me as I want (I think I get a /48 by default, I guess if I want more than 64k subnets I’d have to justify it)

So I don’t have the changing ip issue. I do however have an issue if I want to change ISP as it’s a whole mess of rules to update rather than a couple of dns entries and two dst nat rule (one per public IP)

I believe the idea in v6 if you have multiple prefixes on the same network - including a local fc00::/7 one for local services. Layers and layers of things to break.

ebiederm

6 hours ago

Odd.

Using Openwrt which pretty much all home routers are built on, all I have to do is tell my router which offset to give my subnets from the prefix and it does the rest.

Both for subdividing up the prefix from the ISP and my ULA prefix I use for internal devices.

I have changed ISPs I think 3 times with no ill effects. Plus it works when my ISP occasionally gives me a new prefix.

The only tweaking I had to do was when I went from an ISP that game me a /48 to one that only gave me a /56. I had been greedy and was handing a /56 to my internal router. I changed that to a /60 and updates it's expectations about which subnets it could hand out and all was good.

But I expect two layers of home routers without NAT is a bit of an exception.

karlshea

5 hours ago

Use a ULA (unique local address) for everything internal that you want shorter. It's just like rfc1918 addresses except you don't need NAT.

bcoates

5 hours ago

Is reverse dns even a thing outside of irc and forgetting to give command line tools the "don’t be slow" flag?

esseph

5 hours ago

If you run a traceroute with DNS on, that is referencing DNS PTR records of those IP addresses.

(same for ping)

Sleaker

5 hours ago

Well.. that's because with ipv6 you're not technically on a lan everything is exposed by default unless you set it all up differently.

ekr____

8 hours ago

Well, for some value of "just works".

For example, I recently attended the IETF meeting in Montreal, which offers a by default v6-only network. My Mac worked fine, but my son's school-issued Chromebook had glitchy behavior until I switched to the network that provided v4.

phito

9 hours ago

Myeah... I've had weird issues on my network that I could only resolve by disabling IPv6. Granted, it's probably my fault, but if everything still works fine with ipv4 that's fine to me. One day I will get into it and learn how it work and maybe I'll get it figured out... One day...

mightyham

8 hours ago

For consumer traffic, your probably right. In data centers, cloud computing, and various enterprise networking solutions, IPv4 is still king. I'm sure IPv6 would work fine in all these use cases, but as long as many large tech companies are not exhausting the CIDR ranges they own (or can opt for using private ranges) there is no impetus to rework existing network infrastructure.

opan

9 hours ago

I had working IPv6 in the past, but currently I seem to have no working IPv6. Using Xfinity. I have access to some servers at a friend's place in another city, pretty sure he also doesn't have IPv6. Maybe some phone calls would sort it out, but when "everything" still works (with IPv4), it's hard to care.

bigstrat2003

9 hours ago

That is really bizarre, because I have Comcast and I find their IPv6 support excellent. The only complaints I have are that I wish you could get bigger than a /60 prefix (a /56 would be nice), and that I wish it was feasible to get a static prefix as a residential customer. Granted you said you don't really care to fix it, but if that ever changes I do think you could get them to fix it pretty easily. IPv6 is one of the things they generally do right.

oarsinsync

9 hours ago

Curious what you’re doing that requires more than 16 SLAAC-enabled subnets (or a lot more non-SLAAC enabled subnets)

hdgvhicv

8 hours ago

Corporate laptop won’t work (their version of windows seems to require an ipv4 adddess on an interface, not sure if that’s a windows thing or a them thing)

Doesn’t remove the need for nat - my wired IsP might be able to bgp with me, but my backup 5g won’t, and when I want to choose which to send my traffic through with PBR that means natting.

My router doesn’t support 64, so I have to use my isp’s which is speed constrained compared with native 4. Ok that’s on my setup. Haven’t tested my 5g provider and where 64 occurs, I’d hope in their network, but how do I configure my dns64.

Still need to provide v4 at the edge and thus 46 nat so I can reach internal v6 only servers from v4 only locations

Perhaps lost of that is because my router doesn’t do 64, but again that just shows that v4 is still essential. I haven’t found a single service that’s v6 only, so if I have to run a v4 network (even if only as far as a 64 natting device) why bother running two networks, double the opportunity for misconfiguration and thus security holes. Enabling dual v6 on my IoShit network would allow more escape routes for bad traffic, meaning another set of firewall rules to manage. Things like SLACC make it harder to work out what devices are on the network, many end user devices are user hostile now and keeping control of them on v4 alone is less work than in v4 and v6.

labcomputer

8 hours ago

> Doesn’t remove the need for nat - my wired IsP might be able to bgp with me, but my backup 5g won’t, and when I want to choose which to send my traffic through with PBR that means natting.

Yes, it does. You just have each of your routers (wired and 5G) advertise the /64 prefix delegated by each of your ISPs. Your hosts will self-assign a v6 address from each prefix.

To control which link the traffic uses, you just assign router priority in the router advertisement (these are all standard settings in radvd.conf).

> Things like SLACC make it harder to work out what devices are on the network

Again, not true. If you really don’t trust your devices, then DHCP isn’t going to save you. Malicious hosts absolutely can self assign an unused v4 address, and you’ll be none the wiser if you just look at your DHCP leases.

toast0

5 hours ago

> Yes, it does. You just have each of your routers (wired and 5G) advertise the /64 prefix delegated by each of your ISPs. Your hosts will self-assign a v6 address from each prefix.

> To control which link the traffic uses, you just assign router priority in the router advertisement (these are all standard settings in radvd.conf).

Have you done this? Did it actually work for you?

When I tried it, clients would regularly send to router B with an address from router A, and often ignore the priorities. As I understand the RFCs/client behavior, the router priority field is only relevant if multiple prefixes are in a single advertisement, otherwise most recent advertisement wins.

Once you need to aggregate the advertisements, you may as well NAT66, cause it will be easier.

ekr____

8 hours ago

Well, for some value of "just works".

For example, I recently attended the IETF meeting in Montreal--practically the epicenter of v6 thinking--which offers a by default v6-only network. My Mac worked fine, but my son's school-issued Chromebook had glitchy behavior until I switched to the network that provided v4.

6r17

6 hours ago

I'm "niche" - but i had issues with Wireguard being able to connect me through ipv6 to a v4 - other than that i spent most of my time on v6 and as you said it just works

cornonthecobra

7 hours ago

CenturyLink, an ILEC, only offers IPv6 using 6rd gateways. The IPv6 throughput is a fraction of IPv4 and has much higher latency. During peak times, the 6rd gateway saturates, forcing me to stop advertising the prefix to restore internet access. It has been this way for years.

It is also impossible to report IPv6-specific outages. CenturyLink technical support is the worst of the worst, with agents utterly incapable of doing more than pushing a "check ONT" button on their end and scheduling a technician visit with a multiday window. If you ask them for the 6rd configuration information, they act like you're speaking an alien language.

Even among their technicians, IPv6 knowledge is rare. Imagine the guy installing hundreds of dollars of gigabit fibre equipment at your demarc staring you like an idiot because you spoke two extra syllables between "IP" and "address". I'd think the term "IPv6" is chatbot poison if it weren't for the fact it's a human physically in front of me.

The result is their service is effectively IPv4-only.

toast0

5 hours ago

I had CenturyLink CPE that would crash when a fragmented IPv6 transitted it. That was fun :P. They're also all in on PPPoE and at least on my VDSL2 line, didn't enable RFC 4638 (baby jumbos) to get back to MTU 1500. Pretty happy to be on muni fiber now (although the installation cost was huge).

cornonthecobra

5 hours ago

Ya my router has to do tagged PPPoE through the ONT even though I pay for a static /28. At least I don't have to also do RIP for the subnet like Xfinity requires.

Interestingly, if I pay for their IPTV service the internet side becomes a bare ethernet port over which I can do DHCP for the upstream interface and number the downstream subnet out of my /28.

I have debated paying for TV service as a sanity fee.

kstrauser

2 hours ago

Ah, good ol’ CenturyLink: “We put the TTY in TTY.” Be happy it’s not IPv4 over telegraph.

anonym29

2 hours ago

Not all of the skepticism is "does IPv6 work", some of it is "why should I want it as an end user who values privacy and minimal attack surface?"

From my perspective:

• CGNAT is a feature, not a bug. I'm already deliberately behind a commercial VPN exit node shared with thousands of others. Anonymity-by-crowd is the point. IPv6 giving me a globally unique, stable-ish address is a regression.

• NAT + default-deny inbound is simple, effective security. Yes, "NAT isn't a firewall", but a NAT gateway with no port forwards means unsolicited inbound packets don't reach my devices. That's a concrete property I get for free.

• IPv6 adds configuration surface I don't want. Privacy extensions, temporary addresses, RA flags, NDP, DHCPv6 vs SLAAC — these are problems I don't have with IPv4. More features means more things to audit, understand, and misconfigure.

• I already solved "reaching my own stuff" without global addressing. Tailscale/Headscale gives me authenticated, encrypted, NAT-traversing connectivity. It's better than being globally routable.

So yes, my parents are using IPv6 to watch Netflix. They're also not thinking about their threat model. I am, and IPv4-only behind CGNAT + overlay networking serves it well.

"It just works" isn't the bar for me to adopt IPv6. "It serves my goals better than IPv4" is the bar, and IPv6 doesn't meet it. Never has, never will.

IPv6 wasn't designed as "IPv4 with more bits." It was designed as a reimagining of how networks should work: global addressability as a first-class property, stateless autoconfiguration, the assumption that endpoints should be reachable. That philosophy is baked in. For someone like me, whose threat model treats obscurity, indirection, and minimal feature surface as assets, IPv6 isn't just unnecessary, it's ideologically opposed to what I want.

Want me to adopt a new addressing scheme? Give me a new addressing scheme, don't impose an opinionated routing philosophy on me.

paulddraper

9 hours ago

> It just works.

Until you want to like, use GitHub.

notKilgoreTrout

8 hours ago

There is a clean bifurcation between just works and Microsoft compatible.

mahirsaid

7 minutes ago

i don't like how these companies dictate standards. It's always the case, but they do spend a great deal of money making sure practices morph into standards.

paulddraper

6 hours ago

Whoa! Did you see where those goalposts went?

orangeboats

2 hours ago

Your goalpost already moved from "IPv6 just works" to "IPv6-only just works" though. ;)

In all seriousness, I have IPv6 enabled and GitHub works just fine for me. Though at a slower speed sometimes because the IPv4 CGNAT is heavily congested in my area.

esseph

5 hours ago

Yes the largest companies have the most resources. Makes sense.

Most do not.

There are far more single person, small, and mid sized companies that do not.

This includes b2b, regional ISPs, etc.

mightyham

8 hours ago

> Peer-to-peer communications such as gaming usually have to deal with NAT traversal, but with IPv6 this is no longer an issue, especially for multiple gamers using the same connection

You know the list of "benefits" is thin when the second item is entirely theoretical. Even though IPv6 doesn't have to do NAT traversal, it still has to punch through your router's firewall which is effectively the same problem. Most ISP provided home routers simply block all incoming IPv6 traffic unless there is outbound traffic first, and provide little to no support for custom IPv6 rules.

Even if that were not an issue, my bet is that there are close to zero popular games that actually use true peer to peer networking.

themafia

an hour ago

> it still has to punch through your router's firewall

That's why most routers use a stateful firewall. Then nothing has to "punch through" it just has to be established from the local side.

> block all incoming IPv6 traffic unless there is outbound traffic first, and provide little to no support for custom IPv6 rules.

This is why STUN exists.

> my bet is that there are close to zero popular games that actually use true peer to peer networking.

For game state? You're probably right. For low latency voice chat? It's more common than you'd think.

brigade

8 hours ago

Getting a streamer’s IP attracts DDoSes and doxxing, so yeah it’s generally considered a vulnerability to use P2P in games

trashtensor

an hour ago

Not having a congested CGNAT in the mix at 4pm every day is a nice benefit.

mojuba

10 hours ago

> Groups of zeros can be omitted with two colons, but only once in an address (i.e. 2000:1::1, but not 2000::1::1 as that is ambiguous)

Can someone explain why it's ambiguous?

On the subject, IPv6 is one of the strangest inventions on the internet. Its utility and practically are obvious no matter how you look at it except... just one thing.

Network-related things are generally easy to remember and then type from memory: IPv4, domain names, standard port numbers. Back in the day it was the phone numbers, again, easy to remember and dial when you need it. IPv6 is just too long and requires copy/paste all the time. This is the only real reason in my opinion, why IPv6 is doomed to be second-grade citizen for (probably) a few more decades.

clashandcarry

10 hours ago

2000:1::1 would expand to 2000:0001:0000:0000:0000:0000:0000:0001

2000::1::1 could be 2000:0000:0000:0000:0001:0000:0000:001, or 2000:00000000:0001:0000:0000:0000:001

There's ambiguity on where to fill in the five groups of 0000 in the second case.

rockskon

9 hours ago

The second address is invalid. You can only use :: once per address.

Edit: Whoops. Didn't read what the above post was in response to. My bad.

tpetry

9 hours ago

That exactly what was the question about and they explained why it is invalid…

throw0101c

10 hours ago

> This is the only real reason in my opinion, why IPv6 is doomed to be second-grade citizen for (probably) a few more decades.

Except if you're using a mobile phone, in which case many telcos hand out only IPv6 addresses to handsets. 2018 NANOG presentation "T-Mobile's journey to IPv6":

* https://www.youtube.com/watch?v=d6oBCYHzrTA

From 2014, "Case Study: T-Mobile US Goes IPv6-only Using 464XLAT":

* https://www.internetsociety.org/deploy360/2014/case-study-t-...

But who cares about mobile phones, right? They're only second-grade devices.

ck2

9 hours ago

my tmobile 5g modem has ipv4 but changes ip every single page load, it's wild

I'm used to cablemodems with static ipv4 for months basically until mac changes

hylaride

8 hours ago

> my tmobile 5g modem has ipv4 but changes ip every single page load, it's wild

They're probably using CG-NAT, though IP changes that often is a bit aggressive.

WarOnPrivacy

7 hours ago

> They're probably using CG-NAT, though IP changes that often is a bit aggressive.

TMobile uses IPv4 addys in DOD's address space. They do change unexpectedly often.

And yeah. Being DOD IPs, they're cgnat'd behind tmobile's public ASN.

immibis

5 hours ago

Your IPv4 packets are getting tunneled to a CGNAT server which has an IP address pool.

Your website will load faster on cellphones if it supports IPv6. This is because the packets take more direct routes (because they don't go to the central CGNAT server) and because less processing is applied to them. Almost all mobile networks are now IPv6-only, with IPv4 traffic tunneled and CGNATted. Apparently T-Mobile is the rare exception.

nwellinghoff

10 hours ago

I said this in a previous post and was shot down hard. I think you are right. Every time I look at a ipv6 address my brain goes “fack this”.

WarOnPrivacy

10 hours ago

> Every time I look at a [long] ipv6 address my brain goes “fack this”.

I do get that but I also get 'There are so many I could have all I wanted ... or I could if any of our fiber ISPs would support it, that is'

hdgvhicv

8 hours ago

I finally clicked when I worked out it was 2^64 subnets . You have a common prefix of you /48, which isn’t much longer than an ipv4 address - especially as it seems everything is 2001::/16, which means you basically have to remember a 32 bit network prefix just like 12.45.67.8/32.

That becomes 2001:0c2d:4308::/48 instead

After that you just need to remember the subnet number and the host number. If you remember 12.45.67.8 maps to 192.168.13.7 you might have

2001:0c2d:4308:13::7

So subnet “13” and host “7”

It’s not much different to remebering 12.45.67.8>192.168.13.7

WarOnPrivacy

8 hours ago

> especially as it seems everything is 2001::/16

I was sort of expecting that this week.

I had to transcribe a v6 addy for a WAN-WAN test (a few mi apart).

That's when I noticed that Charter (Spectrum) had issued

   2603:: for one WAN and 
   2602:: for the other WAN.
ref: https://bgp.he.net/AS33363#_prefixes6

mike_d

10 hours ago

IPv4 isn't perfect, but it was designed to solve a specific set of problems.

IPv6 was designed by political process. Go around the room to each engineer and solve for their pet peeve to in turn rally enough support to move the proposal forward. As a bunch of computer people realized how hard politics were they swore never to do it again and made the address size so laughably large that it was "solved" once and for all.

I firmly believe that if they had adopted any other strategy where addresses could be meaningfully understood and worked with by the least skilled network operators, we would have had "IPv6" adoption 10 years ago.

My personal preference would have been to open up class E space (240-255.*) and claw back the 6 /8s Amazon is hoarding, be smarter about allocations going forward, and make fees logarithmic based on the number of addresses you hold.

throw0101c

9 hours ago

> IPv4 isn't perfect, but it was designed to solve a specific set of problems.

IPv4 was not designed as such, but as an academic exercise. It was an experiment. An experiment that "escape the lab". This is per Vint Cerf:

* https://www.pcmag.com/news/north-america-exhausts-ipv4-addre...

And if you think there wasn't politics in iPv4 you're dead wrong:

* https://spectrum.ieee.org/vint-cerf-mistakes

> IPv6 was designed by political process.

Only if by "political process" you mean a bunch of people got together (physically and virtually) and debated the options and chose what they thought was best. The criteria for choosing IPng were documented:

* https://datatracker.ietf.org/doc/html/rfc1726

There were a number of proposals, and three finalists, with SIPP being chosen:

* https://datatracker.ietf.org/doc/html/rfc1752

> I firmly believe that if they had adopted any other strategy where addresses could be meaningfully understood and worked with by the least skilled network operators, we would have had "IPv6" adoption 10 years ago.

The primary reason for IPng was >32 bits of address space. The only way to make them shorter is to have fewer bits, which completely defeats the purpose of the endeavour.

There was no way to move from 32-bits to >32-bits without every network stack of every device element (host, gateway, firewall, application, etc) getting new code. Anything that changed the type and size of sockaddr->sa_family (plus things like new DNS resource record types: A is 32-bit only; see addrinfo->ai_family) would require new code.

mike_d

8 hours ago

This is a lot of basically sharpshooting, but I will address your last point:

> There was no way to move from 32-bits to >32-bits without every network stack of every device element (host, gateway, firewall, application, etc) getting new code. Anything that changed the type and size of sockaddr->sa_family (plus things like new DNS resource record types: A is 32-bit only; see addrinfo->ai_family) would require new code.

That is simply not true. We had one bit left (the reserved/"evil" bit) in IPv4 headers that could have been used to flag that the first N bytes of the payload were an additional IPv4.1 header indicating additional routing information. Packets would continue to transit existing networks and "4.1" capable boxes at edges could read the additional information to make further routing decisions inside of a network. It would have effectively used IPv4 as the core transport network and each connected network (think ASN) having a handful of routed /32s.

Overlay networks are widely deployed and have very minor technical issues.

But that would have only addressed the numbering exhaustion issues. Engineers often get caught in the "well if I am changing this code anyway" trap.

adrian_b

7 hours ago

An explicit goal of IPv6 considered as important as the address expansion was the simplification of the packet header, by having fewer fields and which are correctly aligned, not like in the IPv4 header, in order to enable faster hardware routing.

The scheme described by you fails to achieve this goal.

mike_d

6 hours ago

I am glad you brought this up, that is another big issue with IPv6. A lot of the problems it was trying to solve literally don't exist anymore.

Header processing and alignment were an issue in the 90s when routers repurposed generic components. Now we have modern custom ASICs that can handle IPv4 inside of a GRE tunnel on a VLAN over MPLS at line rate. I have switches in my house that do 780 Gbps.

adrian_b

5 hours ago

It is irrelevant what we can do now.

At the time when it was designed, IPv6 was well designed, much better than IPv4, which was normal after all the experience accumulated while using IPv4 for many years.

The designers of IPv6 have made only one mistake, but it was a huge mistake. The IPv4 address space should have been included in the IPv6 space, allowing transparent intercommunication between any IP addresses, regardless whether they were old IPv4 addresses or new IPv6 addresses.

This is the mistake that has made the transition to IPv6 so slow.

yjftsjthsd-h

3 hours ago

> The IPv4 address space should have been included in the IPv6 space, allowing transparent intercommunication between any IP addresses, regardless whether they were old IPv4 addresses or new IPv6 addresses.

How would you have implemented it that is different from the NAT64 that actually exists, including shoving all IPv4 addresses into 64:ff9b::/96?

shawabawa3

7 hours ago

Imo they should have just clawed 1 or 2 bits out of the ipv4 header for additional routing and called it good enough

immibis

5 hours ago

This would require new software and new ASICs on all hosts and routers and wouldn't be compatible with the old system. If you're going to cause all those things, might as well add 96 new bits instead of just 2 new bits, so you won't have the same problem again soon.

immibis

5 hours ago

IPv6 is literally just IPv4 + longer addresses + really minor tweaks (like no checksum) + things you don't have to use (like SLAAC). Is that not what you wanted? What did you want?

And what's wrong with a newer version of a thing solving all the problems people had with it...?

There are more people than IPv4 addresses, so the pigeonhole principle says you can't give every person an IPv4 address, never mind when you add servers as well. Expanding the address space by 6% does absolute nothing to solve anything and I'm confused about why you think it would.

boob

10 hours ago

> Can someone explain why it's ambiguous?

Because you don’t know how many zeroes are on each side around the 0001 in the middle.

It can be 2000:0000:1:0000:0000:0000:0000:1 or 2000:0000:0000:0000:0000:1:0000:1 etc.

koakuma-chan

10 hours ago

This shortcut system of ipv6 only makes it worse. It's too hard to remember how it works.

icedchai

10 hours ago

Is it really hard to remember? A hint is in the syntax itself. What's in between the two colons '::'? Nothing. In other words, all zeros.

IPv4 also has a similar, though rarely documented or utilized, shortcut system. Try `ping 1.1` for example. It expands to 1.0.0.1.

karlshea

10 hours ago

":: is all zeros" is too hard??

webignition

9 hours ago

How many zeros?

db48x

9 hours ago

Exactly enough to fill out the address, which is always the same length. BTW, IPv4 does basically the same thing. The address 127.1 is equivalent to 127.0.0.1.

integralid

8 hours ago

Not really the same, the mechanics are different and this particular behaviour is pretty much an accident, not abbreviation.

In IPv4 you also have 127.257 equal to 127.0.1.1, 123456789 equal to 7.91.205.21, and 010.010.010.010 is a well-know DNS server. This notation is also rejected by most implementations.

icedchai

3 hours ago

It is? Those alternate IPv4 notations are all accepted by Linux, FreeBSD, and MacOS. I remember playing around with "alternate notations" 30+ years ago on old SunOS boxes.

karlshea

5 hours ago

But IPv6 is "too hard"

karlshea

5 hours ago

There are a total of 8 groups of 4 hex digits, so 8 minus however many groups you already have.

google.com: 2607:f8b0:4009:819::200e (5 groups) -> 2607:f8b0:4009:0819:0000:0000:0000:200e (3 groups of added zeros)

a ULA address: fd2a:1::2 (3 groups) -> fd2a:0001:0000:0000:0000:0000:0000:0002 (5 added)

localhost: ::1 -> 0000:0000:0000:0000:0000:0000:0000:0001

jstanley

9 hours ago

However many are left. In what circumstances do you care?

kstrauser

9 hours ago

However many it takes to make the whole A::B number exactly 128 bits long.

koakuma-chan

9 hours ago

It's not just ":: is all zeroes"

ninkendo

9 hours ago

… such as?

DaSHacka

8 hours ago

https://news.ycombinator.com/item?id=46338674

Dylan16807

6 hours ago

That's a post about invalid things that are not IPv6 addresses.

In IPv6 addresses, :: is all zeroes and there's no ambiguity.

WarOnPrivacy

7 hours ago

I am not clear what your point is. The parent's point stands. A double colon only represents zeros (that were compressed and are not displayed).

Your link does not show different addresses from a valid compression, it shows different addresses from an invalid compression. The link examples what we don't do.

Conversely, if we compress the expanded addresses in your link, we will get 2 different compressed addresses.

WarOnPrivacy

10 hours ago

> Network-related things are generally easy to .. type from memory [but] IPv6 is just too long

I was reminded of this 2d ago; I was testing one IPv6 WAN from another. DDNS had failed so I didn't have my usual crutch to lean on.

ekropotin

10 hours ago

I mean yes, but there’s no escape from the fact that ip addresses need to be longer as amount of devices on the internet already exhausted the pool of IPv4 addresses by multiple orders of magnitude.

I guess it could be possible to implement sort of mnemonic phrases for addresses, à la bip-39, but it would be just trading one kind of pain for another.

api

10 hours ago

I've said this since time immemorial, and networking people often dismiss it. "Just use DNS," say people who have never actually worked netops or devops.

The length of the addresses and the clunky nature of their ASCII representation is absolutely the #1 reason the IPv6 has taken this long. User experience is the most powerful force affecting large scale adoption, and IPv6 has poor UX.

I think the UX is partly fixable by creating less horrible ASCII representation, but this would take a lot of coordination that was hard even back then and is virtually impossible now. If someone told me in 500 years we're still running dual-stack IPv4/IPv6 absolutely unchanged, I'd believe it.

zamadatix

9 hours ago

Half the reason (literally) the address looks so bad is not because of IPv6 but because everyone keeps choosing to implement randomized in-subnet addresses and cycle through them for privacy reasons.

E.g. 2600:15a3:7020:4c51::52/64 is not too horrible but 2600:15a3:7020:4c51:3268:b4c4:dd7b:789/64 is a monster by unrelated intent of the client.

flumpcakes

8 hours ago

This is pretty much on the money. IPv6 addressing can be pretty simple if you design your subnets and use low numbers for hosts. But hosts themselves will forgo that and randomly generate 64 bit random host addresses for themselves - some times for every new connection. Now you have thousands of IPv6 addresses for a single computer speaking out to the Internet.

"Modern" tooling in the consumer space is pretty dire for IPv6 support too. The best you can reasonably get is an IPv6 on the WAN side and then just IPv4 for everything local. At least from the popular routers I've experienced lately.

api

7 hours ago

I’ve been amazed for years at the fact that many of the best routers turn V6 off by default.

Of course I know why. If you turn it on it slightly increases edge case issues as complexity always does. Most people don’t actively need it so nobody notices.

api

8 hours ago

Yes, I forgot about SLAAC and worthless privacy extensions.

Privacy extensions are worthless because there are just sooooo many ways to fingerprint and track you. If you are not at least using a VPN and a jailed privacy mode browser at a bare minimum, you are toast. If you’re serious about privacy you have to use stuff like Tor.

V6 privacy extensions are like the GDPR cookie nonsense: ineffective countermeasures with annoying side effects.

SLAAC sucks too. They should have left assignment up to admins or higher level protocols like with V4. It’s better that way.

immibis

5 hours ago

Privacy extensions are the reason your ISP can't make you pay money for the number of internet-connected devices at your house.

api

5 hours ago

I think you just changed my mind. I hadn’t thought about that angle.

kstrauser

2 hours ago

Respect for considering new information.

ggm

10 hours ago

whats the rule to say where the first 1 floats between the 2000: and the :1 at the end? the :: rule says "all zeros" but not how long.

db48x

7 hours ago

It’s a really complicated rule called “subtraction”. Addresses are always 128 bits long, or 8 groups of four hex digits. 2000::1 is two groups, so you need six groups in between to make 2000:0000:0000:0000:0000:0000:0000:1. But I don’t know why people always ask this, because it’s always the computer you are typing addresses in to that does the subtraction. You never ever have to type out the whole address. Just type the shortened version, because 2000::1 _is_ the whole address.

Dylan16807

6 hours ago

They were answering the question of why "2000::1::1" would be ambiguous if it was allowed.

doubletwoyou

10 hours ago

the :1 is short for :0001 basically and then just put that bit of the address at the very end and put the first bit of the address at the front, and then just fill each missing group inbetween with 0000

webignition

9 hours ago

"just"

bigstrat2003

9 hours ago

Yes, in fact "just". This isn't remotely hard.

karlshea

5 hours ago

These types of complaints are how I know the objection to v6 is not serious.

ggm

7 hours ago

My answer was too terse. IF there was two :: in the address, then the length of EACH :: denoted section is not known. It can be either longest left :: or longest right :: and that wasn't defined, because the rule is THERE IS ONLY ONE :: section.

Posed as a question, disingenuously.

yjftsjthsd-h

3 hours ago

> I spent a WEEK without IPv4 to understand IPv6 transition mechanisms

> NAT64 - the method I’ve setup for this test

> IPv6 is absolutely ready for prime-time and has been for awhile

So... No, you spent a week effectively using both v6 and v4 with extra steps. If someone said "Linux is ready for primetime" but their setup only worked because they ran a bunch of applications in a Windows VM, I'd call that strong evidence that it really wasn't. Same here.

That said... This is from early 2023. Any chance it's better now?

rendaw

2 hours ago

None of the ISPs where I live provide NAT64 gateways. Exactly one advertised it, I signed up almost a year ago and they still haven't enabled it for me yet (I think they don't actually offer it and just forgot to remove the page).

mlangenberg

10 hours ago

> There are also still a lot of misconceptions from network administrators who are scared of or don’t properly understand IPv6

Enable IPv6 on a TP-Link Omada router (ER7212PC) and all internal services are exposed to the outside world as there is no default IPv6 deny-all rule and no IPv6 firewall. I get why some people are nervous.

jeroenhd

7 hours ago

That's more proof that TP-Link should not be trusted than that there is a problem with IPv6, really. Even cheap $20 Aliexpress routers have a firewall enabled by default.

gz09

10 hours ago

I believe that was more a bug in the firmware that's been fixed for a while now.

throw0101c

9 hours ago

> Enable IPv6 on a TP-Link Omada router (ER7212PC) and all internal services are exposed to the outside world as there is no default IPv6 deny-all rule and no IPv6 firewall. I get why some people are nervous.

A router routing traffic makes people nervous? Isn't that what it's supposed to do? I'd be annoyed if my router did not pass traffic.

Now, if the ER7212PC was a firewall that would be something else.

(And no, I'm not being pedantic: routers should pass traffic unless told otherwise, firewalls should block traffic unless told otherwise. The purposes of the two device classes are different, they just happen to both deal with Layer 3 protocol data units.)

baobun

8 hours ago

Routers and access points are also typically separate device classes. Yet the market has figured out that most consumers prefer all-in-one devices. Expecting households to run dedicated firewalls besides their AiO wifi-routers is ludicrous.

What firewall do you recommend a typical user couple their ER7212PC (which BTW is already tripling as VPN gateway and cloud-controller) with?

The problem is that TP-link does not give two cents to security in their products.

> And no, I'm not being pedantic

You very much are.

flumpcakes

8 hours ago

You are of course correct, but most people will disagree because the world we live in is a lot messier than what we should do and people expect a base line. You have to remember that people rely on IPv4 NATing for security, despite every network engineer knowing that is it is not - in effect it is.

tsimionescu

8 hours ago

Are you suggesting that people should buy both a router and a firewall for their home networks? I suppose they should buy a separate Wi-Fi AP as well, and a switch or two, in your opinion?

zajio1am

8 hours ago

'firewall' is just a colloquial term for packet filtering, which is a term for a class of functionality that could be provided by a router.

Customer edge routers are expected to contain firewall (see RFC 7084 and RFC 6092).

shrx

7 hours ago

People expect their router to act as a firewall too, via NAT. If you take this away and force people to buy an additional piece of hardware to restore the expected functionality, they won't switch. Simple as that.

tsimionescu

5 hours ago

All modern NAT routers include a firewall. They don't "act as a firewall too, via NAT", they have both NAT and firewall functionality, even for IPv4. It has been like this for a long time now.

dpkirchner

5 hours ago

I try enabling IPv6 every year or so. The last time I tried IPv6 at home I couldn't figure out what my netmask was, nor the size of my allocation. Some folks say my ISP issues /60s, others /64. I couldn't figure out how to get my IP to remain static long enough to have long-running TCP sessions, either. It was a mess and not much better than it was 20 years ago when I first tried it (and had to disable it because it being on broke all sorts of things).

Maybe 2026 will be the year of IPv6. I kinda doubt it given I'm some jackass and dedicated network professionals still don't use IPv6.

ianburrell

an hour ago

Why are you setting up anything? You turn on IPv6, the router figures out its prefix from the upstream router, and then router broadcasts the network to devices.

The netmask for IPv6 is nearly always /64. ISPs give out /60 to allow multiple subnets, but router makes /64 subnets from that.

illusive4080

2 hours ago

If you have ATT fiber, it’s a pain in the butt. Their default router will only issue a single passthrough /64 on request. If you have multiple VLANs you have to setup some scripts to ask for more, and even then you only get 8 of them. The gateway reserves the other 8 from the /60 it gets for its own use.

The only way I got IPv6 working well with them was to bypass their gateway. Now all my VLANs have /64, which is the standard subnet size.

karlshea

10 hours ago

My two IPv6 issues (even having had a HE tunnel in the past):

- My local ISP (US Internet, soon to be part of T-Mobile Fiber) hasn't enabled it, even though the CEO has said on Reddit for years that it's a priority. Now that they've been acquired who knows if it'll ever happen.

- Linode allows transferring v4 addresses between machines, so if I need to rebuild something I can do so without involving my client who usually has control over DNS. They do not support moving v6 addresses, which means that the only sites I have control over that support v6 are the ones that I control DNS.

Making IPv6 a thing seems like it would be super easy if a couple hours could be spent solving a bunch of dumb lazy problems.

toast0

10 hours ago

> My local ISP (US Internet, soon to be part of T-Mobile Fiber) hasn't enabled it, even though the CEO has said on Reddit for years that it's a priority. Now that they've been acquired who knows if it'll ever happen.

Being a priority doesn't mean it's high priority. It could be a priority, but the lowest ranked one, so other stuff always comes first. :P

T-Mobile wireless US is pretty invested on IPv6, so if they take over the network, they may well push it.

karlshea

5 hours ago

It "finally hit the top of the project list" two years ago so we'll see lol.

It's "T-Mobile Fiber Home Internet" which looks to be a bunch of local ISPs they've been snatching up, so we'll see what happens. USI's customer service and reliability have been amazing so hopefully that doesn't get screwed up.

wolrah

9 hours ago

> Don’t blame your provider when they deploy CG-NAT, embrace IPv6 and global routing instead.

In theory this makes sense, but in practice my personal experience is that not a single wireline ISP I've ever seen deploy CG-NAT offered IPv6 service at all, nor did any of them indicate any intent or even interest when asked about it.

The mobile providers on the other hand have almost entirely gone IPv6-first, using 6>4 transition methods as the default form of v4 access which I fully support.

4>4 CG-NAT should never have existed and providers who deploy it without offering fully functional v6 should be shamed.

PaulKeeble

10 hours ago

When I moved to an ISP that supported IPv6 earlier this year I ran into niggly problems. Ubuntu failed to update because one of its regional servers was misconfigured. OpenDNS one of its servers seemed not to be there on a regular basis over IPv6. I also had odd behaviour and latency issues where sometimes IPv6 would fail to route for short periods and it would fail and fall back to IPv4.

It was a painful experience of trying to work out if I had misconfigured it, if it was something to do with my opensource router software or if it was my ISP or the end services. I didn't get to the end of working this out and reporting issues and I just gave up. Due to the intermittent nature of the issues I was facing I never managed to get a report of issues my ISP would accept.

So I'll give it some time and give it a try after a year and see if things have improved, but it was definitely not ready for prime time.

idatum

9 hours ago

OpenBSD makes it easy to try IPv6 tunnelbroker.net with NAT64/DNS64 if your ISP only has IPv4 ("one more lab test away.." they say).

This has worked for me well for a couple years. I do use a VLAN to keep the IPv6-only network separate (homelab) from video streamers in the household.

In my pf.conf:

    # IPv6 tunnel
    block in log on $tun6_if all
    block in quick on $tun6_if inet6 from fd00::/8 to any
    antispoof quick for $tun6_if
    # allowed icmp6
    pass in quick log on $tun6_if inet6 proto icmp6 icmp6-type {
        unreach, toobig, timex, paramprob, echoreq
    }
    # MSS clamping 60 bytes less than HE 1480
    # 20 byte IPv4 tcp header + 40 byte IPv6 ip header
    match on $tun6_if all scrub (random-id max-mss 1420)
and in /var/unbound/etc/unbound.conf:

    # DNS64/NAT64
    module-config: "dns64 validator iterator"
    dns64-prefix: 64:ff9b::/96
Done. I don't have 464XLAT on Win11 but I do want to know if there's a hard coded IPv4 address anyway. I never had an issue.

idatum

5 hours ago

Forgot the most important part of pf.conf!

    # NAT64
    pass in inet6 from any to $nat64_prefix af-to inet from ($ext_if)

flumpcakes

8 hours ago

I'm very surprised by the questions in this thread. There are some extremely basic things people are just not understanding. I suspect people hating on IPv6 have not spent the time with it. There is a difficulty in that it does behave quite differently to IPv4, and the lack of private addresses are also probably a shock.

transcriptase

7 hours ago

The basic thing proponents don’t understand is that nobody in their right mind can intuitively understand IPV6 addresses because they look like MAC addresses with trisomy and are a pain in the ass to remember or type for absolutely no benefit to the non-network engineer. And there are infinitely more people with home routers and a few dozen devices than there are people running ISPs, fortune 500s, and data centres. Play with your convolution all you want, in 20 years the rest of us will still be happily assigning 192.168.x.x and ignoring it. V4 space running out is no more the average persons problem than undersea cables or certificate authority.

Dylan16807

6 hours ago

> nobody in their right mind can intuitively understand IPV6 addresses

If someone can't understand "it's longer" then what is wrong with them?

And using hex instead of decimal for magic computer numbers should be more intuitive, not less.

Also structure-wise the first half is the subnet and the second half is the host. That's much more intuitive than IPv4.

> absolutely no benefit to the non-network engineer

If you do anything peer to peer at all, calls or file transfers or games, there's a benefit. And the typical benefit grows over time as more and more ISPs install CGNAT.

transcriptase

6 hours ago

> And using hex instead of decimal for magic computer numbers should be more intuitive, not less.

How? Why is using hex any more intuitive than binary or a md5 hash for anyone who doesn’t do networking for a living?

>If you do anything peer to peer at all, calls or file transfers or games, there's a benefit. And the typical benefit grows over time as more and more ISPs install CGNAT.

Again how? I’ve been doing all of those without issue for nearly 30 years. What measurable benefit does the user see that hasn’t been a solved problem since Windows XP?

Will my teams calls suddenly stop saying “poor network connection” on my 1000/1000 rock solid fibre connection? Will torrents suddenly find more seeds and peers? Will my games… have lower latency? Because I can’t think of another way anything networking related could be solved that wasn’t decades ago.

When you say benefit, it should probably be noticeable or measurable in some way that doesn’t involve dashboards and millions of dollars in rack mounted gear.

Dylan16807

5 hours ago

> What measurable benefit does the user see that hasn’t been a solved problem since Windows XP?

Things being able to connect, and not having to manually port forward (when that's even an option).

Hole punching is super unreliable with CGNAT.

> Will my teams calls suddenly stop saying “poor network connection” on my 1000/1000 rock solid fibre connection?

I don't know how Teams relays data, but for some services yes that could happen if IPv4 can't make a direct connection.

> Will torrents suddenly find more seeds and peers?

Yes. In a typical torrent an annoyingly small fraction of seeds and peers can receive connections. If you're IPv4-only behind CGNAT, you can't connect to them and they can't connect to you. IPv6 opens up a lot more links.

> Will my games… have lower latency?

It depends on how the game is designed. But some games will have lower latency because they can connect people directly instead of with relays.

orangeboats

2 hours ago

>How? Why is using hex any more intuitive than binary or a md5 hash for anyone who doesn’t do networking for a living?

Well, what is the address range for 192.168.0.0/27? That's also non-intuitive for a layman as well.

In the end, IP addresses are made for computers, not humans.

And... just FYI,

>Will torrents suddenly find more seeds and peers?

Suggests to me you have absolutely never tried out torrenting under CGNAT. It's painful.

Not a single seeder can _actively_ send the data to you, your client must seek them by itself and it's not uncommon to have only 1-4 seeders connected!

mzajc

2 hours ago

> Also structure-wise the first half is the subnet and the second half is the host. That's much more intuitive than IPv4.

This only applies to /64 blocks, which are by no means standard. For instance, tunnelbroker.net will give you a /48 for free. This means IPv6 addresses are essentially free by the billions, but it's difficult to figure out how big of a block they belong to from the outside.

orangeboats

2 hours ago

Regardless of the prefix size, a subnet is always /64 in IPv6. A shorter prefix simply means you can have more /64 subnets.

justsomehnguy

2 hours ago

> intuitively understand IPV6 addresses because they look like MAC addresses with trisomy and are a pain in the ass to remember or type

I have north of 500 IPs I have some relation to. No way I would be bothered to remember them. Typing? Do you type IPv4s all day long? And it's still copy-paste 99% of times.

> for absolutely no benefit to the non-network engineer

Non-network engineer should work with names. And non-engineers don't 'work' with IPs at all. Look at your granpa - he's typing 'bbc' into the search form in the browser to get to bbc.com.

> nobody in their right mind can intuitively understand IPV6 addresses

And 99% of so called engineers can't understand even IPv4. So this is a moot point.

tgsovlerkhgsel

25 minutes ago

I haven't spent a lot of time with my power grid either, but I do expect the light to go on when I press the switch.

(Needing to dedicate time for it is, to some extent, either a failure of the protocol or at least a contributor to the lack of adoption.)

themafia

an hour ago

> There is a difficulty in that it does behave quite differently to IPv4

Which can be fine if you have a /solid/ transition plan to move networks wholesale from v4 to v6. They absolutely failed on this point and almost purposefully refused to carry over any familiar mechanisms to make dual stack easier to manage.

It's a University protocol that escaped into commercial usage based mostly on false fears of global routing table size becoming unmanageable or impossible to store in RAM. The results are absolutely predictable.

Dylan16807

8 hours ago

Am I missing something? Where's the part where he actually talks about his experience in that week? This goes straight from an overview of IPv6 to the conclusions section.

seviu

6 hours ago

And despite that, the place where I work, has disabled ipv6, rendering our development machines useless for trivial tasks such as debugging our iOS app on a device (which uses ipv6 under the hood)

Reasons given: the security policies say ipv6 is not safe enough.

daft_pink

4 hours ago

I feel this doesn’t really address whether we are losing something privacy or security related by not having NAT. I think my main devices are always updated Mac iPhone or iPad and can handle it, but do I really want my thermostat or doorbell or lock or garage door opener or light switch directly accessible on the Internet or is the nat serving a useful purpose? I don’t feel like this is addressed in this article.

yjftsjthsd-h

3 hours ago

> but do I really want my thermostat or doorbell or lock or garage door opener or light switch directly accessible on the Internet or is the nat serving a useful purpose?

You should have a firewall, regardless of v4/v6.

mzajc

2 hours ago

You should, but the exposure from having no firewall is much higher without NAT. Packets with private network IPs are martians on the internet and will not find their way to your device unless they come from the same network and the ISP's infrastructure doesn't drop them. IPv6 addresses are routable across the internet so the packets will most likely get to your router, meaning anyone on the internet can talk to your LAN in the absence of a firewall.

The reality is that consumer router firmware is horrible in every aspect, especially security, and this isn't going to change with IPv6 rollout. I fear the most likely scenario is that ISPs will set up inbound firewalls on their end, and then we'll be even worse off than we are right now.

transitorykris

3 hours ago

In my 25 year career in network engineering, I’ve encounter needing it as a user exactly once, and that was earlier this year. Supabase’s free tier allows direct connections the Postgres only over IPv6. It’s too bad the deploment has been a long drawn and expensive process for everyone.

glitchc

11 hours ago

While these articles are useful in understanding the utility of IPv6, what would really help is an article explaining step by step how to configure a home network using IPv6. The tutorial should answer these questions:

- How to ensure there are no collisions in address space? Translates to, how to pick safe addresses, is there a system?

- How do I route from an external network resource to an internal network resource? Translates to, can you provide syntax on how to connect to an smb share? Set up a web service that works without WireGuard or equivalent?

- How does one segment networks, configure a vlan, set up a firewall?

candiddevmike

10 hours ago

- if you're talking a private/local prefix, you can use tools like this to generate one: https://unique-local-ipv6.com/. Otherwise DHCPv6 and SLAAC will ensure no collisions for the most part.

- Use global/public addresses on all your devices (using something like prefix delegation) or use NAT.

- Same as IPv4. Prefix delegation will let your ISP assign you multiple networks, and then most routers will break these up into /64 networks for each of your VLANs.

Latty

10 hours ago

- SLAAC - the address spaces for IPv6 are so huge, collisions are extremely unlikely outside of intentional actions.

- Open holes through firewalls, point DNS at the address, and it should just work, the joys of actually having public addresses.

- Same way as with IPv4 mostly. The only real difference is because SLAAC assumes a /64 you probably want your networks to be at least that big.

oezi

9 hours ago

> extremely unlikely outside of intentional actions.

But come on! It is a legitimate question, do you just scramble keys when picking an address?

> the joys of actually having public addresses.

If your ISP gives you a static IPv6. Unfortunately in Germany none of the ISP for private users does (last I checked).

db48x

8 hours ago

> do you just scramble keys when picking an address?

No. Your ISP or tunnel broker gives you a network prefix. Then you configure SLAAC to use that prefix and hand out addresses within it. Job done.

For example, the prefix might look like 2001:470:e904::/48. Your computers can use any addresses you want as long as they start with that prefix. Since you don’t want to manually hand out addresses to every computer, you configure a router to hand out addresses via SLAAC. Your computers will use SLAAC to discover the prefix from the router, then fill in the bottom 64 bits of the address with a random number. They then ask the local network if anyone is using that full address. If not then they are done and have a working address. If somehow someone is using that address then they try again with a different random number. Servers that want a fixed address will just use their network card’s MAC address (or anything similar, if you want) instead of a random number. The protocol is the same either way.

Notice that this actually gives you some bits of your own to play with, if you want. The full address is 128 bits long. The first 48 were used by the prefix and the bottom 64 by the individual devices, leaving 16 bits in the middle. You could tell your router that the prefix for SLAAC is 2001:470:e904:42::/64, for example, and then use the other subnets for other purposes. Maybe 2001:470:e904:beef::/64 is a special subnet just for your meat freezer and associated monitoring equipment. I don't know, you get to make these things up for yourself. Maybe you manage a corporate network that has a separate VLAN for phones than for normal PCs, and a third VLAN for the guest WiFi. You can give them each a different prefix by embedding the VLAN id into the prefix you advertise via SLAAC.

There’s also DHCPv6 if you want even more control over which addresses are handed out, or you want to subdivide your network even more finely. Or if ISPs ever start handing out smaller prefixes.

> If your ISP gives you a static IPv6. Unfortunately in Germany none of the ISP for private users does (last I checked).

Sure, that’s true. But they probably don’t hand out static addresses for IPv4 either. Not without paying extra, that’s for sure. Either way if you want some static identifier for your computer(s) then the solution is the same: DNS.

Of course if you _are_ running a corporate network with a bunch of VLANS like that then you should actually get your own prefix from your RIR rather than from your ISP. Then you purchase IP transit services from your ISP rather than consumer internet access. You can then advertise your prefix(es) via BGP. Again, this is exactly what you would do for IPv4. Same software, same configuration, just longer addresses. The main advantage of this extra work is that you can keep your addresses static even if you move to an entirely different ISP. You can also use the same addresses over multiple connections to multiple ISPs for better redundancy.

flumpcakes

8 hours ago

This is a good overview. I think the difficulty with IPv6 is that people rely on all of the crutches invented for IPv4 as features: private addressing NATing gives you security (it doesn't) and portability (it does), IPv6 usually uses subnets per physical location making failover difficult, where as IPv4 will use bgp announcements to failover public IPs, etc. I'm not saying one way is better than the other, just that IPv6 is pretty different and people very much have a IPv4 world view.

imathew

8 hours ago

My ISP has good IPv6 support. I was using it for a while and recently disabled it across my home network for simplicity of maintenance, cutting my vyos config in half. When I need to access something not available on IPv4 I'll set it up again but I'm not convinced that will happen in my lifetime.

candiddevmike

11 hours ago

I wish I could switch my network to all IPv6 and use NAT64/DNS64, but Android, the world's most popular OS, purposefully disables DHCPv6. I am forced to support IPv4/DHCPv4 for the foreseeable future to support these broken devices.

throw0101c

9 hours ago

> I wish I could switch my network to all IPv6 and use NAT64/DNS64, but Android, the world's most popular OS, purposefully disables DHCPv6.

It does not "disable" DHCPv6. It does not support DHCPv6. Android (really Lorenzo Colitti) in/famously WONTFIX adding DHCPv6 client support:

* https://issuetracker.google.com/issues/36949085

Of course after over a decade of denying that Android needs some kind of DHCP in IPv6, it seems that Android may finally be getting some kind of solution:

* https://android-developers.googleblog.com/2025/09/simplifyin...

* Via: https://blog.ipspace.net/2025/09/android-dhcpv6-prefix-deleg...

Hopefully, having admitted (?) the error of their ways with being SLAAC-only they'll also add 'regular' DHCPv6 in addition to DHCPv6-PD.

franklyworks

10 hours ago

Android supports SLAAC and has good support transitional tech like xlat464 and DHCP option 108.

I have used these on my network and office to move to IPv6-only for Android.

What about lack of DHCPv6 prevents you from using IPv6 on Android?

candiddevmike

10 hours ago

I can't run SLAAC and DHCPv6 at the same time without giving devices multiple addresses, and Android doesn't support DHCPv6, so I'd have to carve out a separate, SLAAC-based, android-only network. And then figure out firewall rules, multicast reflection, etc.

justincormack

10 hours ago

Why is giving multiple addresses a problem?

candiddevmike

10 hours ago

No control over which source address is used. I'm assigning a lot of clients DHCP reservations so I can use static addresses for monitoring and firewall rules. With multiple addresses on the same network, clients may use their SLAAC address which won't match the firewall rule.

db48x

7 hours ago

That still doesn’t really make sense. Why not run SLAAC on one subnet and have a single firewall rule for the whole thing? You’re not running any major servers on an Android phone, so it won’t be anything complex.

tsimionescu

5 hours ago

SLAAC can only run on a subnet that's larger than /64, which they might not have access to.

gspr

10 hours ago

I thought this was a problem too. Then I realized that addresses are not in short supply, so I stopped caring that some devices get multiple addresses. The ones I care about are handed out over DHCPv6, and the firewall works accordingly. The rest gets basic connectivity and nothing else.

Works great for me.

candiddevmike

10 hours ago

Don't you have problems with clients using the wrong source address and not matching firewall rules?

kstrauser

an hour ago

Different person here, but no. I never write firewall rules based on individual source addresses. They’re too easy to fake. And with IPv6’s privacy extensions, you never know what source address a given machine will have anyway.

gspr

9 hours ago

No. Admittedly, my firewall rules are all about granting something extra beyond the basics. I only do this for clients I care about anyway, so I can always tell them to use the right address.

dmm

10 hours ago

Android supports DHCPv6, just not stateful DHCPv6. You can give each device its own /64 or if you really want to track a devices usage you should use an authenticated layer on top of your base network.

avidiax

10 hours ago

Why can't you use stateless autoconfig?

candiddevmike

10 hours ago

Because I want to control the suffix assigned to devices for firewall rules and monitoring purposes.

avidiax

7 hours ago

Seems like the wrong layer unless your network has more than one router/gateway.

Use MAC as the key for firewall and monitoring. Then you don't have multiple rules per device.

suprjami

9 hours ago

World IPv6 day 6-6-26, just turn IPv4 off. Let the world catch up.

I said the same thing for 6-6-16 too.

martinald

3 hours ago

Interesting. I did finally find a use for IPv6 which I wrote up here: https://martinalderson.com/posts/i-finally-found-a-use-for-i...

Tbh though the docker problems are very serious and extremely painful to work around. Everything works great apart from Docker which has so many issues - it does not handle IPv6 inbound but IPv4 out well at all (at least as far as I can tell!).

rao-v

10 hours ago

What’s the pragmatic solution to ipv6 allowing everybody in my household to be trivially and stably mapped to a unique subnet? I like the accidental semi-randomization that ipv4 and ISP NAT offered and I don’t see anything like it short of putting my entire home net on a VPN (it’s expensive and can’t keep up with my ISP’s bandwidth)

lloeki

10 hours ago

Each device gets directly addressable from WAN with v6 but it also gets a randomised privacy IP that rotates very frequently so each individual device is just as "hidden" as it was with v4+NAT.

Your v6 subnet prefix is no different than whatever WAN-side v4 your NAT had. "Accidental semi-randomization" of the WAN side IP is not something one could reliably count on. Many ISPs just hand over a static-like IP, that is, even when it's supposed to be random the pool of IPs is so constrained that it's usually the same simply through the IP lease surviving power cycling. And that was before CGNAT.

If your concern is being identifiable through your IP then counting on whatever v4 artifact is the wrong move. Use a VPN with randomised exit nodes.

icedchai

3 hours ago

Everybody in your household is already mapped to a single IPv4 address that rarely changes with most ISPs. Mine hasn't changed in over 3 years. My IPv6 /56 prefix delegation hasn't changed, either.

yjftsjthsd-h

10 hours ago

It's true that you won't get CGNAT without having CGNAT. Depending on your concern, it is possible to NAT66 to make your entire network appear as one IP.

illusive4080

2 hours ago

AWS doesn’t offer PTR records for IPv6 addresses, which makes Gmail blacklist my email server’s IPv6 address. I had to disable IPv6 due to lack of PTR records.

1970-01-01

8 hours ago

I have firsthand experience doing that experiment about 3 months ago. Completely removed my IP4 DHCP lease from my ISP at the router. About 50% of the public sites I tried to visit didn't resolve. So many public sites, that I gave up and went back to dual stack after just a day. Google, ChatGPT, and a few other popular sites were fine with pure IPv6 traffic, however sites like eBay and even HN did not resolve. IPv6 simply is still not ready for everyone to just transition into overnight.

tlogan

10 hours ago

As a normal user: why do I need IPv6?

As far as I know, the majority of websites (about 70%) do not support IPv6.

jeroenhd

6 hours ago

Depends on your ISP. If you live in a place where there aren't many IPv4 addresses available, CGNAT is the reason you're seeing a lot of Cloudflare/Akamai/Google CAPTCHAs everywhere, and IPv6 fixes that.

calvinmorrison

4 hours ago

same reasons northern europeans had to invent all sorts of fancy food preservation and complex power struggle societies revolving around crop limitations and war.

Meanwhile closer to the equator, much less progress was needed to live and let live.

In short, Americans are native tribes. we have plentiful IPV4 and couldnt care less about SLAAC or whatever other complex moon sun and seasonal tide gods, salted codfish and salt mining operations. we just dont need to care about long addresses, they're plentiful here.

paulddraper

9 hours ago

You need it because there aren’t enough IPv4.

If you have a mobile device with data, you’re likely already using it.

sethops1

8 hours ago

Do we really need all the mobile phones and IoT devices of the world to be publicly addressable? Is that even a good thing?

paulddraper

8 hours ago

If you want to use the internet, you need an IP address.

You can share that IP address by putting multiple hosts on the same local network and using parts of the transport later. NAT was invented because of lacking enough addresses.

badgersnake

9 hours ago

I don’t think that’s true. But of course it depends how you’re measure the majority of websites.

Most of the figures I see show 60-70% of the top 100 sites do support it. But maybe that does not reflect your usage.

Why do you need it? Maybe you don’t right now since ipv6 only sites are niche. The most tangible advantage I’ve seen is avoiding CGNAT. Gamers in particular don’t like that because it introduces latency. Services like Xbox live definitely do support ipv6 for this reason.

layer8

9 hours ago

If Google would announce that Chrome is dropping IPv4 support in n months, that would probably get things moving. ;)

stevekemp

9 hours ago

I guess it would, but remember there are more services out there than just HTTP(S).

For example the last time I had an IPv6-only host I had issues cloning things from github, as "git clone git@github.com..." failed due to github.com not having IPv6 records.

A quick search revealed this open 3+ year old discussion - https://github.com/orgs/community/discussions/10539

ChrisMarshallNY

8 hours ago

I'm pretty underwhelmed by IPv6. It looks like the typical "horse designed by committee."

I suspect that what will actually end up being implemented, will be a core subset of the spec.

We'll have to see what's still standing, when the dust settles.

jeroenhd

6 hours ago

The IPv6 spec looks long because it also includes protocols that are separate on IPv4 (DHCP/SLAAC, NDP, depending on the document ICMPv6, mirroring DHCP, ARP, ICMP, NetBIOS, etc.), as well as the addressing schemes that were different RFCs in IPv4 such as multicast/unicast/network classes/subnets.

As for the implementation: just about anything more powerful than an ESP32 has the entire protocol implemented and running already.

ChrisMarshallNY

6 hours ago

As long as the SDKs to apps make it simple, we'll be good. I haven't seen much, so far.

db48x

7 hours ago

Your computer, and every other computer on the planet, already supports the entire IPv6 spec. There is no subset.

yjftsjthsd-h

3 hours ago

I'm typing this on a computer running Android, which means it doesn't support DHCPv6. I would describe it as supporting a subset of IPv6 functionality.

ChrisMarshallNY

7 hours ago

Well, we'll have to see what all the "in-between" bits do. There's a lot in it, that will require implementation by countless layers of routers, switches, caches, firewalls, etc.

Look at Bluetooth, for an example, or TIFF.

I printed out the Bluetooth spec once, just for Ss and Gs. It was over 2,000 pages (double-sided).

I once tried writing a fully-compliant TIFF reader. Didn't go so well.

db48x

7 hours ago

Those all support IPv6 too. They’re the same computers, and they’ve all supported IPv6 for decades now. The IPv6 spec is a lot shorter than the spec for Bluetooth or TIFF.

ChrisMarshallNY

7 hours ago

Just because the physical and link layers support it, doesn't mean the application layer will.

You could say the same for Bluetooth chips.

I've seen stuff, man...

kalleboo

2 hours ago

Apple requires that all iOS apps on the store function on an IPv6-only network (which is how several large mobile phone networks work), and everything works fine on the application layer.

ChrisMarshallNY

3 minutes ago

Huh. I believe that, but didn’t know it (I write apps for Apple kit). I have done low-level networking stuff that would definitely have run into issues, but that was over ten years ago. These days, I rely on the upper layer of the stack.

I really should try an exercise like the one the author did. I’m not necessarily against IPv6, but I’m still a bit skeptical of it. We’ll likely be forced into it, as there’s no alternative, but that’s not exactly a ringing endorsement.

razighter777

6 hours ago

The workarounds we need to enable P2P communication on the internet are a shame... we need turn, stun, webrtc, all this stuff so two computers can talk without a dedicated port forward or public ipv4.

ipv6 is a beautiful protocol, (not perfect, but elegant) with a lot going for it. But the momentum of ipv4 is just too strong.

It's a mess... with no good solution. I tried to turn off ipv4 and github (shame on you) stopped working. But what are we supposed to do? Have the government mandate everyone switch? (oh wait half of US government websites are ipv4 only)

We did this to ourselves...

jyscao

10 hours ago

I need to switch my home network to at least use IPv6 externally, because my ISP recently deployed CG-NAT, which made my SSH server that used to work no longer reachable from outside of my LAN.

bakugo

10 hours ago

You can use a NAT-traversing VPN like tailscale to work around this.

sneak

2 hours ago

I tried that, but my HN addiction ended it.

ianburrell

an hour ago

HN has IPv6 now.

If Reddit would finish adding IPv6, almost all of my browsing would be IPv6.

self_awareness

3 hours ago

My ISP has IPv6 since years and I'm on 6 as well.

NAT-less network is really cool, I can serve content directly from anything from my LAN.

We should really leave IPv4 and move on.

avidiax

10 hours ago

People keep saying that IPv6 allows you to more easily host services, but you still have to support IPv4.

Try connecting to your IPv6-only service on Hotel WiFi -- you usually can't.

It's unfortunate, but IPv6 doesn't really solve any problems for a home user. And I say this as someone that has deployed IPv6 at home before.

mattypg

10 hours ago

> It's unfortunate, but IPv6 doesn't really solve any problems for a home user.

CG-NAT and strict NAT in general. Newer ISPs often force users onto CG-NAT, and my consoles have had numerous issues with NAT in general over the years. ISP routers also often make fixing this an opaque or impossible problem for the user.

I don’t think IPv6 is the best thing ever, but I do think it solves the problems IPv4 did along with some annoying issues IPv4 struggled with.

brandonkal

10 hours ago

It does make it easier. IPv6 pinholes are simpler than port forwarding. My IPv4 is not static but my IPv6 prefix is. So I don’t need dynamic DNS. I have no IPv4 port forwards, instead I run snid on a VPS to support legacy internet clients and call it a day.

avidiax

7 hours ago

https://github.com/AGWA/snid

So you basically have a cloud server and a domain with a wildcard record, and you then forward IPv4 through IPv6?

I think this somewhat proves my point that IPv6 doesn't solve much for self-hosting. You still need some kind of working IPv4 setup. You are using IPv6 in place of either a reverse proxy or something like tailscale, which I suppose is more convenient.

kachapopopow

8 hours ago

the reason why I explicitely disable ipv6 cause "this shit don't work" (at the moment, will probably change in the future)

- random slowdowns

- horrible routing

- larger packet overhead

- hated by a lot of the people who run the internet

- hated by companies who provide ddos protection

- my poor TCAM cache in my budget routers

- supporting ipv6 is really expensive in chassis routers

However, I believe there is a solution: Swap ISP's to IPv6 only, swap to IPv4 unless there is an IPv6 route present then directly forward. This solves quite a few issues: Once every ISP has IPv6 you can drop ipv4 and swap directly to ipv6 without having to split your TCAM. This works because IPv6 can encode IPv4 in it.

jrm4

10 hours ago

Hot take: IPv4 might be techinically worse, but it's "politically" (in the classic sense of the word) better.

IPv6 essentially enables "universal internet IDs" for every device, which could streamline a lot of things, but enable a lot of weird surveillance/power balance issues that the cruft of IPv4 is actually incidentally helping guard against.

Again, I'm old enough to remember when e.g. the ISPs were going to try to charge per device in each household.

ninkendo

9 hours ago

This hasn’t been the case in decades, every OS defaults to randomly generating the trailing 64 bits of your address and cycling through new addresses periodically. Your IPv6 address is only fixed to your device if you choose to configure it that way.

Since the network half (leading 64 bits) is as fixed as your IPv4 address was, and the host half is random and constantly changing, an IPv6 address is exactly as uniquely identifying as an IPv4 address used to be.

blahaj

10 hours ago

> Again, I'm old enough to remember when e.g. the ISPs were going to try to charge per device in each household.

I don't really see that coming again and if it does you can just do NAT66 just like you can do NAT4.

jrm4

10 hours ago

You and I can, yes.

But, network effects.