2 servers on 2 PCs on the same network

[keltuze]

• Does anyone have experience with configuring two servers on the same network (one dedicated IP address on the outside)? I was able to configure for example 192.168.1.102 and open ports 27000, 27003,27020,27021 for it.
  As per the instructions, I duplicated these ports to be equivalent to TCP and UDP.
  The 1st server is running on a separate 4790k hardware with people playing on it for years.

  I then decided to set up a test server on my own 8700k PC.
  In the NAT router I duplicated all the settings from above, but specified them for my personal machine 192.168.1.103.
  In Settings.ini I specified port 7777, opened it with the appropriate udp and tcp.

  What I have as a result
  Every time I run my second test server on my personal machine - people complain that they stop seeing my primary server in the server browser, which is actually broadcasting from ip 102.
  I've tried different ways to change these settings, but no results.
  I'm also confused by the fact that my 102 machine has port 27000, but when I try to connect to it on the LAN it doesn't ping 27000, instead I've tried 192.168.1.1.102:27003 and it pings at that address, how do I understand this?

  Can anyone tell me a working way to do this? I have been hosting for 7 years now
  
  
  UPD.I did it differently, I allowed all ports to the main server 1. and the number 2 test server only allowed the specified port 7777. Now I can see the main machine on the network with name and description. And the test machine 2, without name(ip:port), and for some reason it took the description of the main machine 1. 

Edited July 28 by keltuze