I have this set up in my house. I have a tld and internally I want the IP to resolve to the land IP and externally, to the ISP ip. I also have local caching f

I have this set up in my house. I have a tld and internally I want the IP to resolve to the land IP and externally, to the ISP ip. I also have local caching for things like imap, but slow uploaded so I don't host my full email and web mail stack there. I run 2 dns servers usually on the same box on different bind addresses. You'd run a caching resolver on the gw ip and forward requests for my.tld to the second resolver which is configured to be authoritative for my.tld. the hosts can then be configured either through DHCP or statically. This is a pretty common technique to make enterprises Intranets. Added benefit is that when you did a file transfer between Lan hosts with the globally accessable DNS, the transfer stays on the LAN. Also ssh host works in you ssh config regardless of location.