Before I installed unbound I just had dnsmasq running for DNS.
The WAN interface uses the peer DNS and the LAN interface had not DHCP options set, it was happily running dynamic DHCP and advertising the router as DNS server.
DHCP stopped advertising the router as DNS server after I installed unbound (i think in serial to dnsmasq, also to support DHCP). I used the config option Link to dnsmasq in LUCI UI.
Sure I can put in 6,"router-ip" as DHCP option to fix it, but that is not really elegant.
How can the old default behavior be restored? Was any configuration inadvertantly changed by the installation?
I don't understand what would be the problem with 2 interfaces. The DHCP options are defined per interface, not globally. on the UI just go to Network>Interfaces>LAN>Advanced Setting>DHCP Server>Advanced Settings>DHCP Options. Same from DMZ or what ever internal lan. Take a look at this UCI example for 2 lans called lan and DMZ:
Thanks I tested it with wireshark. the DHCP server will really replace the 0.0.0.0 with the IP of the respective interface from where it is sending the packet. That's awsome advice!
-- Maybe I was a bit too fast or too enthusiastic. Acually I received some DHCP ACK not containing the DNS Server option when it was set to 0.0.0.0 Setting it back to the actual IP made the option re-appear. But also setting it to 0.0.0.0 then worked again - I guess I have to keep an eye on it for now.
Just to be clear for the people wondering: the problem that @jus7incase doesn't understand is that some people doesn't use DNSMASQ, making this solution useless for odhcpd. Not trying to say this does not work, don't get me wrong. But people using odhcpd will lost their DHCP server without reason and it's worth saying it.
Neither of both. I replaced DNSMASQ with odhcpd and unbound to keep attack surface, ROM and RAM as tidy as possible. It's well documented in the wiki but I'm mainly here to say people to not try this with odhcpd because it will make it immediately crash and then enter in a crash loop.
This problem is not present when using odhcpd, by the way so it's not worth trying.