How to handle routing with overlapping ranges as general concept?

[dmoviesad]

An existing network managed by a 3rd party contains routers of the same subnet (in this case 192.168.0.0/24) and is connected to a central infrastructure using a VPN tunnel. All connections are force to go through the tunnel, i.e. Router A and Router B are not able to directly communicate with each other, but only to send and receive packages through the tunnel. The routers manage internal networks with overlapping ranges between them. There is no way to change the Router Network or its configuration.

For a custom, arbitrary central instance where the tunnel terminates, I am looking for a solution to connect the routers with additional external networks. For those, again an IPsec tunnel is established, and again we might have overlapping IP addresses.

Simplified, I am looking for a way to provide routing according to the dotted lines in scale. My main problem are the overlapping network ranges, and the individual target routers of the 192.168.0.0/24 range.

What method / technology of dynamic routing would you suggest to create virtual networks containing the corresponding pairs (Router N, Cloud Network N)? From my understanding BGP won't help here, as I couldn't define a distinct set of AS without overlapping range. Could you please push me in a direction to look into?

[balaji.bandi]

If you have Overlapping IP address i can think of NAT using unique address space to communicate each other. (that is the best each way to communicate)

you can find many examples overlap IP address and Natting.

example :

https://www.cisco.com/c/en/us/support/docs/ip/network-address-translation-nat/13774-3.html

[M02@rt37]

Hello @dmoviesad,

You are correct that traditional methods like BGP may not be suitable due to the overlapping IP ranges.

You could consider:

NAT and Static Routes:

Use NAT to translate IP addresses between overlapping subnets, allowing communication between the networks. Configure static routes on the routers involved to direct traffic to the correct destinations based on the translated addresses.

VRF:

Implement VRF on your routers to create separate routing instances. This allows you to have overlapping IP ranges in different VRFs without conflict.

Use VRF-lite on routers that support it, or MPLS/VPN technology if available, to maintain separation and allow routing between networks.