Editing DNS in the manual DHCP assignments vs. DNS Director

[mrric]

What is the difference between these two options? I see that I can assign (1) DNS server to a specific client in both these options.

My goal is to assign a Primary and Secondary DNS server to a smart thermostat while having all my other devices use the DNS I have configured in the WAN - Internet Connection tab. I don't want the stat to drop connection if it can't reach the (1) DNS server configured in one of those options.

 

[bennor]

DNS Director can be used among other things to "supersede" what ever one has configured for the LAN DHCP DNS servers or have configured per client via the manual IP address reservation DNS option. And DNS Director can be used to "supersede" a client's hard coded DNS server as well. Note the information on DNS Director page (following from 3006.102.x firmware):

DNS Director

DNS Director allows you to force LAN devices to use a specific DNS server, which can be useful if you want to force them to use a filtering service that would block malicious or adult sites. You can set a global network-wide server, or client-specific servers. Beside the available presets you can also define up to three different custom servers to use.
A few special System options are available in the presets. "No Redirection" will bypass a global redirection, and "Router" will force clients to use the router itself as their resolver.

PS: And while a bit dated, from the Asus-Merlin Wiki:

DNS Director

Third party firmware for Asus routers (newer codebase) - RMerl/asuswrt-merlin.ng

github.com