I run a network with a router from my ISP and a WiFi access point from TP-Link. The access point has a static IP address (192.168.0.100) and its DHCP server is disabled.
My computer runs Linux with
dnsmasq enabled and employs it as its primary name server. I expected this server to forward all requests that it cannot resolve to the DNS server of my ISP router and, therefore, the domain that is supposed to lead to the web interface of the TP-Link router,
tplinkwifi.net, to stop working.
I was very surprised when I saw that this domain is in fact still resolved to 192.168.0.100. Tracing the DNS lookup didn't clear up my confusion: It seems like it is actually a global DNS server that responds with the respective IP address from my local network:
$ dig +trace tplinkwifi.net ; <<>> DiG 9.11.25-RedHat-9.11.25-2.fc33 <<>> +trace tplinkwifi.net ;; global options: +cmd . 5693 IN NS h.root-servers.net. . 5693 IN NS a.root-servers.net. . 5693 IN NS l.root-servers.net. . 5693 IN NS b.root-servers.net. . 5693 IN NS f.root-servers.net. . 5693 IN NS g.root-servers.net. . 5693 IN NS i.root-servers.net. . 5693 IN NS e.root-servers.net. . 5693 IN NS k.root-servers.net. . 5693 IN NS m.root-servers.net. . 5693 IN NS d.root-servers.net. . 5693 IN NS j.root-servers.net. . 5693 IN NS c.root-servers.net. ;; Received 262 bytes from 127.0.0.53#53(127.0.0.53) in 0 ms tplinkwifi.net. 0 IN A 192.168.0.100 ;; Received 48 bytes from 184.108.40.206#53(i.root-servers.net) in 83 ms
How is this possible?