On internal network I have a client and a server. Server is hosting example.com and fake.example.com that are also open to the internet through NAT. Any computer on the internet can access example.com or fake.example.com, but internal computers get redirected to router page when accessing either either site. How do I troubleshoot this issue, or what things should I take a look at?
Server: 10.10.0.10 with NAT route to public ip x.x.x.170 Client(s): 10.10.0.100 with NAT route to public ip x.x.x.174
example.com A record is set to x.x.x.170 so is fake.example.com
nslookup example.com and tracert example.com do indeed come back to x.x.x.170
The device that is performing your NAT simply isn't NATing properly when the request is coming from the internal network. This is common; Cisco ASAs have this "problem" by default. Depending on your device, you may be able to configure it to allow this type of connection (commonly called a "hairpin"), or it may not be possible and you'll have to have DNS resolve differently for internal clients.