Linking Two Routers With Same IP

RouterOS Beginner Basics
1

Greetings,

I have two separate routers running well in two buildings next to each others with no issues but now i need some of the devices to communicate between networks so i installed a new cable to link them together. the issue i am facing is that the two routers have the same router ip and subnet.

here is a diagram to explain more:

Router 1: is provided by ISP. they don’t allow much editing capabilities of configuration but i was able to enable secondary dhcp address (192.168.100.1/24). also it is not possible to change the main router ip and dhcp (192.168.1.1/24)

Router 2: is Mikrotik Hex router replacing ISP box. (ether5) is free and can be used to link with Router 1. also is very hard to change main router address since i have multiple clients already configured.

I just need PC2 & PC3 from Router 2 to reach the Server (192.168.1.10 or 192.168.100.10) in Router 1. is that possible without changing any of the routers main ip and subnet?

any suggestion is welcome. i really appreciate it.

2

192.168.100.10 is outside pc2 & 3 network, so the packets will be sent to router 2.
Use something like 192.168.50.1/30 at router 1 and 192.168.50.2/30 at router 2 for connection between routers.
On router 2 you will need a route pointing to gateway 192.168.50.1 for destination 192.168.100.0/24
Then on router 2, masquerade the packets going out on interface connecting the 2 routers.
PCC 2 & 3 should then have communications to subnet 192.168.100.0/24