How to set up communication between the same subnets?

Question

Cisco

How to set up communication between pc1 and pc3 (they are on the same subnet)? between pc1 and pc2 configured static routing

Answer 1

I don't see any problems. Or little input.
2811 already has static routing.
Everything else is switching.
Therefore, if they are in the same flat network, then they see each other.

Answer 2

Either redo the scheme so that devices from the same subnet are connected to one interface of the router, or try to configure /32 routes, incl. on the hosts themselves. You can also experiment with proxy arp on router interfaces.

Answer 3

Enter ps3 in the same vlan as ps1. Previously, of course, having forwarded it along the entire chain.

Answer 4

The question is strangely structured. How can they be on the same subnet? Have you configured bridge-domain? By default, the router will not let you stretch one broadcast domain over two of its interfaces.
Or is your pc3 aggregated on the far right of the C2560 and is there a binding between it and the L3 router? Then everything is simple - read about source/destination NAT. If I'm not mistaken, Cisco calls it twice NAT. Look here and here