Why doesn't Zentyal allow you to register the addresses of both interfaces on the same network?

Question

Computer networks

The server has 2 interfaces, traditionally eth0 and eth1. I need to set the address 192.168.0.2 on one interface (which, in fact, will drive packets further to the tlink router), and 192.168.0.5 on the second, which will be distributed by the dhcp server as the gateway address.
Having successfully registered the address of the first interface, I try to register the address of the second one, to which I receive a curse of a similar plan: "It is not possible to use the address 192.168.0.5, since the eth0 interface already uses the same addresses in its network."
How to deal with it? Do not offer to transfer the router to another network - some devices must go outside bypassing the gateway