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Comment by dpkirchner | Hacker News Reader

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.

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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.

Nah. There are lots of things you’ll need to know.

Does it use SLAAC on the WAN side or DHCPv6? How do I get a range for my lan then, DHCPv6 prefix-delegation? Or maybe it’s statically assigned somehow. Some carrier’s just use link-local ok the WAN, with no public v6 just RAs for the link-local, and a GUA block via IA_PD.

Regardless there are too many ways this is done, and this hampers adoption as it’s not just the “switch it on” operation you suggest.

All of those are handled automatically. The only people who have problems are ones who want to configure manually. More importantly, this is no different than IPv4 where have DHCP or manual.

Nearly every ISP uses DHCPv6-PD cause harder for manual configuration. The range is in the DHCP-PD, your router picks a subnet. The WAN address is automatic, and don't care about it cause never see it. Mine is link-local and hadn't known until I checked.

Not OP, but when I first tried to learn IPv6 for my home internet, I found that it's very important that you get the DHCP-PD prefix size right when configuring your router, or it would just not work at all.

I have Comcast, and they do give me a /56, but you can't ask for a /56 in the DHCP-PD request, because they don't support a single request grabbing all of your prefix space. You have to ask for /60's, which I had to find out through trial and error.

But it may have been even worse (my memory is fuzzy) because I think at one point I did successfully get a /56, but that then exhausted my DHCP allocation, and then after I rebooted my router I couldn't get anything any more. It didn't help that the router I had been using (Unifi security gateway) didn't seem to keep a static DUID that comcast was happy with, so I kept getting new prefixes every time it rebooted.

Comcast probably has so few customers that bring their own cable modem/router at this point that they basically don't have any support for this, you won't get anything from them over the phone, they just push you to pay them to rent their equipment (where they configure all these parts the way their network expects.) You have to be adventurous to run your own equipment with IPv6.

I need to know what IPs they might assign to my network, and then what IPs are to be assigned to my computers (or what I can assign statically).

You find out the addresses after it is configured automatically. This is no different than IPv4 and DHCP.

If you don't want to use the public addresses internally, then you can assign ULA addresses. If you don't want to use MAC derived addresses, assign them static host addresses.

For names, I use mDNS. I don't know the IPv6 address for my server. If I did need it, I would get it from the router.

Probably the largest barrier to IPv6 adoption is the myriad ways IP allocation to clients can be done and the various options that exist.

It’s fine for mobile providers, where the client activation defines what’s needed and the carrier essentially just needs to support two OS’s (iOS and Android).

Also mostly fine for residential when the carrier provides the CPE, and can set it up to work with how they have the network built.

But if you’re managing your own router it can be complex to know exactly what to use. And most ISP support aren’t very good either.

If you happen to be an expert it’s fine, but if you’re a power user not a full time network guy there is still way more complexity than there ought to be.

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.

I think bypassing their gateway, that is - bringing your own router is the only way to do VLANs, because their gateway is very basic and doesn’t support VLANs at all.

You can do VLANs with their gateway but only IPv4, or you have to write custom scripts to ask for additional IPv6 delegations.

Interesting. Which model of their gateway do you have? I have BGW320 and it definitely doesn’t support vlan tagging.

Also BGW320. Maybe I’m not understanding the difference. I had it plugged into my gateway where I did VLANs on the gateway. The BGW320 was in passthrough mode. Yes, by itself it does not support VLAN tagging.

That’s essentially what I said - if you want VLAN tagging, you MUST pass through their gateway, IPv6 or not.

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