The issue I am facing:
I can resolve each of the hostnames I have set up for Pi-hole's localhost, but can't use some of them to ping or visit the host from another computer. pi.hole works, other hostnames don't.
Details about my system:
I have pi-hole installed on a machine that is set up as my router. It's an Ubuntu Server 20.04 system running on an Intel Core2 Duo machine with 4-port NIC bridged to be the LAN interface and the built-in Ethernet interface is the WAN interface. Pi-hole is my DHCP server and DNS server.
What I have changed since installing Pi-hole:
I also have Nagios running on the same machine, and Pi-hole is set up to use port 8080 instead of 80.
Details about problem
Using my primary computer (Windows 10), or other computers on the network, I can resolve the correct IP address using hostnames I have set up, but cannot ping using those same hostnames, and cannot use them to visit the Pi-Hole web interface, for instance. However, pi.hole can be used to ping and visit the web interface of both Pi-hole and Nagios
Here are some examples:
C:\Users\jer_c>nslookup gateway
Server: J-GATEWAY
Address: 192.168.1.1
Name: gateway
Address: 192.168.1.1
C:\Users\jer_c>ping gateway
Ping request could not find host gateway. Please check the name and try again.
C:\Users\jer_c>nslookup router2
Server: J-GATEWAY
Address: 192.168.1.1
Name: router2
Address: 192.168.1.3
C:\Users\jer_c>ping router2
Ping request could not find host router2. Please check the name and try again.
C:\Users\jer_c>nslookup pi.hole
Server: J-GATEWAY
Address: 192.168.1.1
Name: pi.hole
Address: 192.168.1.1
C:\Users\jer_c>ping pi.hole
Pinging pi.hole [192.168.1.1] with 32 bytes of data:
Reply from 192.168.1.1: bytes=32 time<1ms TTL=64
Reply from 192.168.1.1: bytes=32 time<1ms TTL=64
Reply from 192.168.1.1: bytes=32 time<1ms TTL=64
Reply from 192.168.1.1: bytes=32 time<1ms TTL=64
Ping statistics for 192.168.1.1:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 0ms, Average = 0ms