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this post was submitted on 16 Aug 2024
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Question for you since I have very little real world IPv6 experience: generally you can provide a lot of useful network information to clients via DHCP, such as the DNS server, autoconfig info for IP phones, etc. how does a network operator ensure that clients get this information if it's not using DHCPv6?
You can include some information in router advertisements, likely there will be rfcs for more. Not sure of the full list of stuff you can advertise.
For sure I'm quite sure I had dns servers configured this way. I'll check when not on a phone to see what options there are.
If I recall correctly, you can do stateless DHCPv6 to just hand down a DNS server without also managing the devices' IP addresses.
You can, and there's a specific flag to set on nd/ra to tell the client to get other information from djcpv6. But so far I've not made it work and also, it likely won't work on android.
Really the way forward is for routers and devices to implement the same options as exist on dhcp. But, time will tell how that gets on.
This is a weakness of ipv6 but it's really the lack of widespread implementation that's behind this. If we were all using it, there would be more onus to get this stuff working.
What exactly does Google do for Android, then? Hardcode the IPv6 address of their own DNS service, or fall back to pulling AAAA records over IPv4?
Say that you can use prefix delegation. No, really, you can look at the bug report: https://issuetracker.google.com/issues/36949085?pli=1 . It’s absolutely infuriating. Especially when iOS does support it
DHCPv6 is very definitely used with ipv6 and isps, as DHCPv6-PD is needed anyway to send prefix allocations to the router
DHCPv6 does the same thing DHCP does, just for v6 addresses. This includes pushing domain suffix and dns servers.
There is also Router Advertisement, which tells the discovering client that it is a router, what the prefix is, if there is a DHCPv6 server, and what the DNS is. As an alternative to DHCPv6, the client can set their own address based on the combination of the prefix and their MAC address, the SLAAC address. The way IPv6 routing tables are built, the router can always find a route by asking upstream on the address, and upstream only has to forward downstream on an address.