My ISP’s router (ATT fiber) does not support NAT loopback. In my home LAN, I have a Linux machine (Ubuntu 24.04) that runs Apache and serves “my.example.com”. I all port forwarding configured to handle http(s) requests to my Linux machine, and I am able to access “my.example.com” from outside my LAN; but any request to “my.example.com” from within my LAN fails due to NAT loopback support in my router.

However, I noticed that if I use another device within my LAN that run Linux, it is able to successfully resolve “my.example.com” and overcome the NAT lookback issues that my Macs and PCs cannot. How is that possible if I have not set up any host files or dedicated DNS server? Is this something that is Linux specific or rather something to do with the ISP’s router?

Running traceroute in a linux device within my LAN shows (public IP i obscured):

traceroute to my.example.com (77.111.111.111), 30 hops max, 60 byte packets
 1  77-111-111-111.lightspeed.tukrga.sbcglobal.net (77.111.111.111)  3.313 ms  3.610 ms  3.698 ms

However running traceroute in a PC or MAC device within my LAN shows (public IP i obscured):

traceroute to my.example.com (77.111.111.111), 30 hops max, 60 byte packets
 1  77-111-111-111.lightspeed.tukrga.sbcglobal.net (77.111.111.111)  4.313 ms  *  *