Add second DNS IPv6 server without a fixed prefix

[jheredianet]

HI, I don't have a fixed IPv6 prefix, I rather get a new one from the ISP every 24 hours or something.
What I have achieved is that a server on my LAN has a static node address (this will be a second DNS server and other services).

I did this by "IPv6 assignment hint" and setting a static "IPv6 suffix" by DUID

So every time my ISP changes the IPv6 prefix, I know that its IPv6 will be something like this: 2a0c:5a80:xxxx:xxx5::2

What I'd like to do now is how to announce this device as a second DNS server. Now I just have checked "Local IPv6 DNS Server", but I need to add a second server for which I only know the last part of its IPv6 address

I would like to have the same behavior as it delivers the current IPv6 address of the router (which is also variable)
Any idea will be appreciated. Thanks in advance.

[dave14305]

Can you announce a static ULA DHCPv6 assignment for the second DNS server?

[jheredianet]

Yes, I can. But somebody recommend me that if I'm using prefix delegation, it is not necessary to have ULA-prefix, so it's cleaner.

That's why I'm looking is there is other way to do it (maybe a script or some special notation like ::5:0:0:0:2)

[dave14305]

@jheredianet

if I'm using SLAAC it is not necessary to have ULA-prefix

I don’t know that I see the relationship between the two facts, but I’m willing to be open-minded.

[vgaetera]

Consider advertising your local DNS with LLA.

[jheredianet]

I don't know how to do it, could you guide me throw or be more specific?
Thanks.

[jheredianet]

@dave14305 I've learned it from here https://youtu.be/LJPXz8eA3b8?si=B-RTDxBzFSJWY6wu&t=228

[vgaetera]

ip neighbour | grep -i -e DNS_MAC

https://en.wikipedia.org/wiki/Link-local_address#IPv6