Do you actually own that /48? The problem with using the globally routable addresses internally is that your public /48 might change in the future, and and that will force you to change a bunch of internal stuff.
I have my router set up to advertise two /64 prefixes on each LAN subnet: one from fddd:deca:fbad::/56* that I use for all internal communication, and one from 2001:5a8:xxxx:xxxx::/56 that is only used for talking to the internet. Every device I've ever tested supports this configuration flawlessly, including linux/apple/windows laptops, apple/android mobile devices, an IoT vacuum, and a 10+ year old VoIP phone.
My router is a Linux PC, so I can configure radvd however I want (no GUI, I just edit the configs over SSH). Maybe home routers won't let you do this.
* You're really supposed to pick a random prefix in fd00::/8, but uniqueness only matters if you intend to merge networks with somebody else later, I care more about it being easy to remember.
Ideally it'll be standard that your DHCP will assign you both an internet IP from your ISP-provided prefix (dynamic or static), and private IP from a ULA prefix, which can be made static through address reservation.
Don't use DCHPv6 at home. I tried: you will hate your life, lots of stuff doesn't support it. Android specifically has zero support for it, google says it never will.
In my experience the ISP generally fixes a /64 for each customer. So if in the future you change your ISP, you might want to keep the remaining addresses same while just using a script to replace the preceding /64 address.
My ISPs change the /64 more often. So I use the ULA a lot more often. My router runs its own DNS server and then it advertises this DNS server using a ULA address.
Typically it's similar to ipv4, they try to assign the same address/prefix for the same MAC/DUID. The most common reason to lose your addresses is replacing your router. Hopefully new routers allow you to set the dhcpv6 DUID somehow...
I haven't experienced this. For me it's statically assigned but my guess is that the PON serial and/or MAC is being used or the customer ID. I think the ISPs have gotten very automated these days and everything seems to be some sort of SDN. It saves lot of labour hours in troubleshooting like customer forgetting their wifi passwords to their routers.
Interesting. Honestly I like having control over it, that would annoy me. I deliberately change the DUID in dhcpcd to force my public addresses to change every so often.
For my own networks I use the private range internally (fd00::/8). That way the addresses remain the same when we move or change the pipe to a bigger one. Also, they can be routed, just not on the Internet. It's easy to join remote networks over wireguard and there's plenty of room for experimentation.
I find it much simpler for troubleshooting etc to have simple IPv4 addresses. But cool that it can be done :)
I've switched off IPv6 on my router anyway, I haven't yet needed it. My provider didn't offer it last time I checked but when they do enable it I don't want it suddenly popping up against an untested router configuration.
I don't know your background, but I find that the people who feel that there's nothing wrong with IPv4 have never done any work with UPNP or NAT. For them it's always "just worked" and they don't recognise what pain has gone into trying to keep it working well despite our usage of it bordering abusive.
NAT is the devil.
If anyone replies to this with the myth that NAT is a security mechanism I will firmly, yet politely, point them to a network development course because they don't know what they're talking about and I'm sick of hearing it. It's not true, I will not entertain this falsehood anymore.
I dunno, I've manually set up NAT (down to the sysctls and iptables) and it's... fine. There's a small learning curve, but it's small. You should of course run a firewall which NAT is not; that's also simple and just basic hygiene.
Well yes, a stateful NAT is stateful. But as that article notes:
> For most workloads, there’s plenty of headroom in the table and this will never be an issue.
And yes, if you're doing thousands of connections per second then you should evaluate things more carefully for performance, but again... That's rather a lot.
Connection table of a single IP is as high (by default) as 16,383[0].
I've hit this limit personally, and due to limitations in stateful firewalling we had to move to stateless filters inside our network equipment instead.
I do work with NAT, but the stuff I use does hole-punching pretty transparently. I run 2 VPSes to facilitate this. I don't use UPNP, I have it explicitly disabled everywhere (too much malware that tries to leverage it)
And yes I know that NAT has the same effect as a "deny all inbound" on IPv6. Which is something I would set there too if I did use IPv6 so I'd still have to do hole-punching anyway.
I never understood the rationale of giving out /64 and /48 like candy after what happened with ipv4. I know it's still a massive increase in capacity and I know it makes the networking easier but it seems like we went from something that definitely won't run out (ipv6 addresses) to something that probably won't (number of /48 ranges)
I can think of at least two reasons why this isn't worth worrying about.
One is quantitative: you have to remember that 2^48 is a much much bigger number than 2^32. With 2^32 IPv4 addresses, you have about 0.5 addresses per human being on the planet, so right away you can tell that stringent allocation policies will be needed. On the other hand, with 2^48 /48 ranges, there are about 8,000 ranges per human being.
So even if you hand a few /48s out free to literally everyone who asks, the vast majority will still be unallocated. A /48 is only about 0.01% of what could be said to be a "fair" allocation. (And yet, a /48 is so huge in absolute terms that even the vast majority of organizations would never need more than one of them, let alone individuals.)
The other is that unlike, say, the crude oil we pump out of the ground, IP address ranges are a renewable resource. If you hand out a free /48 to every person at birth, then long before you start running out of ranges, people will start dying and you can just reclaim the addresses they were using.
/48s are "small" enough that we could give ~8 billion people each 35,000 of them and we'd still have ~1.5 trillion (over 300x the size of the ipv4 space) left over. Addresses are basically infinite, but routing table entries (which fragmentation necessitates) have a cost.
Yes. I wish they had simply used a more sane address length instead, and maybe given everyone 65535 addresses at most. More than enough for the craziest home lab ever.
Really, just adding 2 bytes to IPv4 would have fixed everything and made it a lot simpler to move over. IPv6 is overkill and I think that really hurt its adoption. I remember being at uni and being told "this is the next big thing". In 1993. And it's not even a big thing now. Not on the user side anyway, I can still access everything from IPv4.
In IPv6 the smallest 'subnet' is /64 if I recall correctly.
It's weird having a subnet size equal to a complete IPv4 Internet worth of IPv6 Internets but I believe the rationale was that you would never in practise run of out IPs in your subnet. A lot of Enterprise IPv4 headaches are managing subnets that are not correctly sized (organic growth, etc.). IPv6 is always routable for the same reason (companies reusing RFC1918 making connecting networks a pain).
There are different headaches with IPv6 - such as re-IPing devices if they move subnet - i.e. move physical location, or during a failover etc.
I'm not sure what the best practise there is as many enterprises don't use IPv6 internally. In my experience anyway.
If we actually get to the point of address shortages,
Either, NATv6 would become a thing, or instead I hope SLAAC would get deprecated and dhcpv6 would become mandatory so we could give out smaller than /64s
2^64 is 18,446,744,073,709,551,616. That's 18 quintillion. 10^19. There are ~10^10 people on the planet. Each person could have a 10^9 networks (not even devices) before we ran out of /64s.
> able to run ~340 undecillion devices on my home network
You now can have these devices connected to network called Internet.
Unlike IPv4 were the number of devices on the Internet in home network is one (the main router) or zero (in case if CGNAT) and the others just pretend.
I suspect I am going to be running dual stack for at least the next decade, IPv4 switch off feels very far away. I don't think there is much advantage or disadvantage to running IPv4 compared to translation. The current internet doesn't feel ready. I have had less issues with IPv6 this year compared to last so there has been some progress but I am still getting fallbacks to IPv4, some companies don't seem to care much about IPv6 outages currently.
Where I live, the benefit of IPv6 is it's a lot faster than IPv4. All of IPv4 goes through various centralized tunnels and CG-NAT which adds bottlenecks and latency.
IPv4 pricing isn't a good enough reason? If all of my devices had nice ipv6 connectivity I could ditch the public ipv4 addresses, but I have to keep them so that my ipv4-only devices can still reach them.
For home use biggest advantage is that it avoids NAT, which breaks end to end connectivity. Lot of services use hacks to try to mitigate broken connectivity.
Even without CGNAT you'll only get one IPv4 address forcing a absurd amount of workarounds to be usable, that are mostly hidden in firmwares but sill there.
Huh, I have matter devices working here and IPv6 is off on my router and DHCP. And on home assistant too which does the matter router. Does it use link local or something?
I attempted a similar effort, and found my router had critical ipv6 vulnerabilities including binding the admin and SSH to the WAN on ipv6 (not on ipv4) , and disabling IPv6 firewall altogether so the LAN services were exposed to the internet.
I had the vendor publish their GPL drop, and their upstream vendor did not even have IPv6 support in the product ( the firmware init scripts & admin UI) . So the IPv6 support in the finished product was a rushed copy-paste of IPv4 setup.
I encourage full black box testing of your IPv6 setup, as IPv6 is not in the critical path for QA or consumers, so vulns can persist for years.
I messed with this at one point and gave up when I realized every device would have a permanent externally addressable IP within a block that is basically linked to me (good luck trying to change your IPv6 /48 every month or whatever you get with consumer IP addresses)
It’s probably not a big deal and NAT etc. is no protection but it gave me the heebie jeebies.
Bad generalization. I'm sure policy about this differs a lot, but my consumer ISP definitely reassigns my home's v4 address periodically. I don't track it closely, but it seems that when my ONT power cycles more often than not it pulls a new v4 address.
Now, basing my privacy/security on this would be bad, but to GP's point, if I was using a static v6 block, not only would this address never change, each device in my LAN would have an extra identifier attached to it. External hosts wouldn't merely be able to identify "my house", but traffic from "my phone", "my kid's switch", and "my spouse's phone" would all have distinct addresses.
Of course, my ISP doesn't do v6 at all, so there's no dilemma :')
Do you actually own that /48? The problem with using the globally routable addresses internally is that your public /48 might change in the future, and and that will force you to change a bunch of internal stuff.
I have my router set up to advertise two /64 prefixes on each LAN subnet: one from fddd:deca:fbad::/56* that I use for all internal communication, and one from 2001:5a8:xxxx:xxxx::/56 that is only used for talking to the internet. Every device I've ever tested supports this configuration flawlessly, including linux/apple/windows laptops, apple/android mobile devices, an IoT vacuum, and a 10+ year old VoIP phone.
My router is a Linux PC, so I can configure radvd however I want (no GUI, I just edit the configs over SSH). Maybe home routers won't let you do this.
* You're really supposed to pick a random prefix in fd00::/8, but uniqueness only matters if you intend to merge networks with somebody else later, I care more about it being easy to remember.
Ideally it'll be standard that your DHCP will assign you both an internet IP from your ISP-provided prefix (dynamic or static), and private IP from a ULA prefix, which can be made static through address reservation.
Don't use DCHPv6 at home. I tried: you will hate your life, lots of stuff doesn't support it. Android specifically has zero support for it, google says it never will.
Use SLAAC. It just works.
>Do you actually own that /48?
In my experience the ISP generally fixes a /64 for each customer. So if in the future you change your ISP, you might want to keep the remaining addresses same while just using a script to replace the preceding /64 address.
My ISPs change the /64 more often. So I use the ULA a lot more often. My router runs its own DNS server and then it advertises this DNS server using a ULA address.
I have mentioned this elsewhere, but ISPs should make BYOIPv6 more common, not just to the Business customers.
Their are people like OP who do this via a VPS provider that supports BYOIP and then tunnel to the VPS network, so there is a demand.
https://news.ycombinator.com/item?id=47355038
Typically it's similar to ipv4, they try to assign the same address/prefix for the same MAC/DUID. The most common reason to lose your addresses is replacing your router. Hopefully new routers allow you to set the dhcpv6 DUID somehow...
I haven't experienced this. For me it's statically assigned but my guess is that the PON serial and/or MAC is being used or the customer ID. I think the ISPs have gotten very automated these days and everything seems to be some sort of SDN. It saves lot of labour hours in troubleshooting like customer forgetting their wifi passwords to their routers.
Interesting. Honestly I like having control over it, that would annoy me. I deliberately change the DUID in dhcpcd to force my public addresses to change every so often.
For my own networks I use the private range internally (fd00::/8). That way the addresses remain the same when we move or change the pipe to a bigger one. Also, they can be routed, just not on the Internet. It's easy to join remote networks over wireguard and there's plenty of room for experimentation.
Why though? What's the problem with ipv4?
I find it much simpler for troubleshooting etc to have simple IPv4 addresses. But cool that it can be done :)
I've switched off IPv6 on my router anyway, I haven't yet needed it. My provider didn't offer it last time I checked but when they do enable it I don't want it suddenly popping up against an untested router configuration.
I don't know your background, but I find that the people who feel that there's nothing wrong with IPv4 have never done any work with UPNP or NAT. For them it's always "just worked" and they don't recognise what pain has gone into trying to keep it working well despite our usage of it bordering abusive.
NAT is the devil.
If anyone replies to this with the myth that NAT is a security mechanism I will firmly, yet politely, point them to a network development course because they don't know what they're talking about and I'm sick of hearing it. It's not true, I will not entertain this falsehood anymore.
I dunno, I've manually set up NAT (down to the sysctls and iptables) and it's... fine. There's a small learning curve, but it's small. You should of course run a firewall which NAT is not; that's also simple and just basic hygiene.
Well, if you've set it up then you're aware that you need conntrack;
Conntrack is not always your friend, and even when it is: it's adding a lot of overhead.
https://www.tigera.io/blog/when-linux-conntrack-is-no-longer...
Well yes, a stateful NAT is stateful. But as that article notes:
> For most workloads, there’s plenty of headroom in the table and this will never be an issue.
And yes, if you're doing thousands of connections per second then you should evaluate things more carefully for performance, but again... That's rather a lot.
It's interesting that you'd think that.
Connection table of a single IP is as high (by default) as 16,383[0].
I've hit this limit personally, and due to limitations in stateful firewalling we had to move to stateless filters inside our network equipment instead.
[0]: https://learn.microsoft.com/en-us/troubleshoot/windows-clien...
I do work with NAT, but the stuff I use does hole-punching pretty transparently. I run 2 VPSes to facilitate this. I don't use UPNP, I have it explicitly disabled everywhere (too much malware that tries to leverage it)
And yes I know that NAT has the same effect as a "deny all inbound" on IPv6. Which is something I would set there too if I did use IPv6 so I'd still have to do hole-punching anyway.
This video summarizes it nicely
https://www.youtube.com/watch?v=42Hy4JtBeQA
Thanks for sharing this! Every few years, i forget the "why" advantage of IPv6. :-)
It looks like an in-kernel replacement for jool is coming
https://lore.kernel.org/netdev/20260319151230.655687-1-ralf@...
That's fantastic news; there weird friction around NAT64 on Linux has been a real pain point.
Finally. I will now be able to run ~340 undecillion devices on my home network. I'll have the smartest "smart home" on the block.
I never understood the rationale of giving out /64 and /48 like candy after what happened with ipv4. I know it's still a massive increase in capacity and I know it makes the networking easier but it seems like we went from something that definitely won't run out (ipv6 addresses) to something that probably won't (number of /48 ranges)
I can think of at least two reasons why this isn't worth worrying about.
One is quantitative: you have to remember that 2^48 is a much much bigger number than 2^32. With 2^32 IPv4 addresses, you have about 0.5 addresses per human being on the planet, so right away you can tell that stringent allocation policies will be needed. On the other hand, with 2^48 /48 ranges, there are about 8,000 ranges per human being.
So even if you hand a few /48s out free to literally everyone who asks, the vast majority will still be unallocated. A /48 is only about 0.01% of what could be said to be a "fair" allocation. (And yet, a /48 is so huge in absolute terms that even the vast majority of organizations would never need more than one of them, let alone individuals.)
The other is that unlike, say, the crude oil we pump out of the ground, IP address ranges are a renewable resource. If you hand out a free /48 to every person at birth, then long before you start running out of ranges, people will start dying and you can just reclaim the addresses they were using.
/48s are "small" enough that we could give ~8 billion people each 35,000 of them and we'd still have ~1.5 trillion (over 300x the size of the ipv4 space) left over. Addresses are basically infinite, but routing table entries (which fragmentation necessitates) have a cost.
Current recommendation (afaict ianant) for ISPs is to give everyone a /56. Not every isp does that, ofc
Yes. I wish they had simply used a more sane address length instead, and maybe given everyone 65535 addresses at most. More than enough for the craziest home lab ever.
Really, just adding 2 bytes to IPv4 would have fixed everything and made it a lot simpler to move over. IPv6 is overkill and I think that really hurt its adoption. I remember being at uni and being told "this is the next big thing". In 1993. And it's not even a big thing now. Not on the user side anyway, I can still access everything from IPv4.
In IPv6 the smallest 'subnet' is /64 if I recall correctly.
It's weird having a subnet size equal to a complete IPv4 Internet worth of IPv6 Internets but I believe the rationale was that you would never in practise run of out IPs in your subnet. A lot of Enterprise IPv4 headaches are managing subnets that are not correctly sized (organic growth, etc.). IPv6 is always routable for the same reason (companies reusing RFC1918 making connecting networks a pain).
There are different headaches with IPv6 - such as re-IPing devices if they move subnet - i.e. move physical location, or during a failover etc.
I'm not sure what the best practise there is as many enterprises don't use IPv6 internally. In my experience anyway.
/48 because ethernet mac addresses are that length and so you can assign everything that and find it.
If we actually get to the point of address shortages,
Either, NATv6 would become a thing, or instead I hope SLAAC would get deprecated and dhcpv6 would become mandatory so we could give out smaller than /64s
2^64 is 18,446,744,073,709,551,616. That's 18 quintillion. 10^19. There are ~10^10 people on the planet. Each person could have a 10^9 networks (not even devices) before we ran out of /64s.
> able to run ~340 undecillion devices on my home network
You now can have these devices connected to network called Internet.
Unlike IPv4 were the number of devices on the Internet in home network is one (the main router) or zero (in case if CGNAT) and the others just pretend.
I suspect I am going to be running dual stack for at least the next decade, IPv4 switch off feels very far away. I don't think there is much advantage or disadvantage to running IPv4 compared to translation. The current internet doesn't feel ready. I have had less issues with IPv6 this year compared to last so there has been some progress but I am still getting fallbacks to IPv4, some companies don't seem to care much about IPv6 outages currently.
Wish I could use ipv6. My ISP doesn’t support it (yea, I know tunnels exists but then it’s just more pain than just using ipv4)
Much less pain than people wanting to have something you could connect to would experience.
I can’t understand benefits of having ipv6. The only one is public ips but rest is just headache. In my home network I specify disabled v6 everywhere.
Where I live, the benefit of IPv6 is it's a lot faster than IPv4. All of IPv4 goes through various centralized tunnels and CG-NAT which adds bottlenecks and latency.
IPv4 pricing isn't a good enough reason? If all of my devices had nice ipv6 connectivity I could ditch the public ipv4 addresses, but I have to keep them so that my ipv4-only devices can still reach them.
imo one huge benefit is that ipv6 is much easer for hardware to process.. ipv4 headers are messy and change size.
ipv6 headers are 40 bytes! routers have less thinking.
this visualisation might help to dive deeper - https://vectree.io/c/ipv6
For home use biggest advantage is that it avoids NAT, which breaks end to end connectivity. Lot of services use hacks to try to mitigate broken connectivity.
video games
It doesn’t matter in home networks, it’s a major pain in the ass if you are a Fortune 500 company and want to set up more intercompany vpn links
A site-to-site VPN of two previously unrelated local networks is a pure gamble with IPv4. It would be almost straight forward with IPv6.
Yes but these days overlay networks are a way more common practice for that, with their own benefits (overlay IPs are always encrypted)
Public IPs is a huge huge huge benefit. Your connection is also faster because your IPv6 packets don't have to be processed by a centralised CGNAT.
That's only if you are behind CGNAT though. My fixed ISP doesn't use it.
Yet.
Many ISPs are pushing v4 users into CGNAT so they're easier and cheaper to manage.
This is a big reason why Netflix and YouTube are on v6. To avoid the cost of service over v4.
Even without CGNAT you'll only get one IPv4 address forcing a absurd amount of workarounds to be usable, that are mostly hidden in firmwares but sill there.
Ipv4 is the headache. What are you talking about, ipv6 is simpler in my experience.
IPv4 is pretty simple and good for LANs. Nothing wrong with sticking to it.
Matter requires IPv6
Huh, I have matter devices working here and IPv6 is off on my router and DHCP. And on home assistant too which does the matter router. Does it use link local or something?
IPv6 isn’t that compelling on a simple home network, but avoiding NAT and easier end-to-end connectivity are pretty real advantages.
I attempted a similar effort, and found my router had critical ipv6 vulnerabilities including binding the admin and SSH to the WAN on ipv6 (not on ipv4) , and disabling IPv6 firewall altogether so the LAN services were exposed to the internet.
I had the vendor publish their GPL drop, and their upstream vendor did not even have IPv6 support in the product ( the firmware init scripts & admin UI) . So the IPv6 support in the finished product was a rushed copy-paste of IPv4 setup.
I encourage full black box testing of your IPv6 setup, as IPv6 is not in the critical path for QA or consumers, so vulns can persist for years.
Dual stack IPv4+IPv6 is still the easiest, but at least the author learned a lot and it helps finding issues in software.
I messed with this at one point and gave up when I realized every device would have a permanent externally addressable IP within a block that is basically linked to me (good luck trying to change your IPv6 /48 every month or whatever you get with consumer IP addresses)
It’s probably not a big deal and NAT etc. is no protection but it gave me the heebie jeebies.
You know your external IPv4 address rarely changes and also basically linked to you too, right?
> your external IPv4 address rarely changes
Bad generalization. I'm sure policy about this differs a lot, but my consumer ISP definitely reassigns my home's v4 address periodically. I don't track it closely, but it seems that when my ONT power cycles more often than not it pulls a new v4 address.
Now, basing my privacy/security on this would be bad, but to GP's point, if I was using a static v6 block, not only would this address never change, each device in my LAN would have an extra identifier attached to it. External hosts wouldn't merely be able to identify "my house", but traffic from "my phone", "my kid's switch", and "my spouse's phone" would all have distinct addresses.
Of course, my ISP doesn't do v6 at all, so there's no dilemma :')
That's also a poor generalization, though. Some ISPs rotate customer subnets, and devices can rotate their randomized IPs.