[Dnsmasq-discuss] Trying to work out correct configuration for dynamic prefix delegation and constructed ranges

[Robert Sharp]

On 03/01/2025 04:32, Nathan Mitchell wrote:
> Is there a way I can accomplish this with dnsmasq? Or am I running 
> into a fundamental design issue with the IPv6 architecture where I'm 
> not supposed to do this? And if so, what is the replacement for the 
> way things worked before in IPv4 land? Because this doesn't seem too 
> crazy to want to do in my mind.
>
> Thanks!
>    -- Nathan

Hi Nathan,

I think that I have this working fine with the following:

# IPv6 stuff
enable-ra

dhcp-range=::FF,::400,constructor:enp3s0,ra-names,24h
dhcp-range=vlan0 at enp3s0,::2,::400,constructor:vlan0,ra-names,24h

dhcp-host=fc:ab:13:c8:90:3e,server,[::5]
dhcp-host=...

I use dhcpcd to obtain and delegate a prefix to each interface and 
dnsmasq hands out addresses to the lan and vlan and resolves names for 
my server(s). Everything has been working fine for a long time now but 
it took quite a bit of fiddling to get it working.

Interesting that your ISP only provides dynamic prefixes. I thought the 
whole point of IPv6 was to provide an address space large enough to 
avoid that. Perhaps they are charging more for static addresses? I have 
a static /48 prefix from my ISP which is just great for the 6 trillion 
devices on my network. But I have been careful not to hard-wire the 
static address into anything so it could be dynamic for all I care.

Robert