Router Advertisements and ULA

[9axqe]

Hello,

I would like to have my devices only get IPs via DHCPv6 on the network, no autoconfiguration. (I want to know which IPv6 belongs to what device, it's a small home network.)

At the same time, I do want to use ULA as a backup: I had a couple of times the issue that my ISP Internet was down and additional opnsense power cycled, causing DHCPv6 acquired prefix to be forgotten by the router. I am aware that the point could be made, IPv4 is already one backup, since it's RFC1918...

Question 1: is there a way for opnsense to keep using the last known DHCPv6 acquired prefix / IP, even after a reboot? (I assume not)

Question 2: if that is not possible, is it possible to assign ULAs over DHCPv6 while using the managed mode for router advertisement?

opnsense 25.1.1 on DEC695

[Bob.Dig]

You can only assign one type via DHCPv6, so the answer is no.

[dseven]

I wonder if OPNsense would ever consider changing that - i.e. allowing a "Managed" ULA and "Unmanaged" "Track Interface" on the same interface simultaneously.

Meanwhile, I think ULA + NPTv6 is the only available solution...

[doktornotor]

I am aware that the point could be made, IPv4 is already one backup, since it's RFC1918...

Do you realize that ULA won't be used at all in dual-stack network?

[dseven]

Do you realize that ULA won't be used at all in dual-stack network?

Only if there are DNS entries for both... e.g. if "thing123.lan" has a v6 static mapping but no v4 static mapping (or maybe doesn't even do v4 at all), it should be reachable via its ULA, even if DNS resolution (on the client trying to access it) was done over IPv4