Network topology trick: system A can connect to B & C n vice versa but B & C shouldn’t connect each other

Let’s play around network and create a setup that we might need for some use case. Create a network topology setup in such a way so that System A can ping to System B and System C but both these systems should not be pinging each other. That so without using any security rule like firewall etc.

network topology to be setup

First launch 3 systems in same network. Here to setup IP as 1, 2 and 3.

Now remove all routes from routing table so we can set it as our need

removed all routes

Now’s to create such setup, in system A add both system B & C routing rules so that A can connect to B & C. Also in B & C add system A’s route so that both can connect to system A.

routes added

All set. Note that system B & C don’t have any rules added for each other so that they both can’t connect to each other.

Finally we can check connectivity by pinging,

setup working

Here we can see that system A can ping to system B & C and vice versa. But system B & C are unreachable to each other..!