Hi, I have a following GNS3 topology where router R1 connects to two different subnets (10.0.0.x/24) and (192.168.0.x/24). Interface g0/0 has 10.0.0.254/24 address and g1/0 has 192.168.0.254/24. There is ethernet switch connected on both sides on which there are three clients each. How can 10.0.0.1/24 reach 192.168.0.1/24? Topology attached.
Since the two networks are directly connected to the same router, you just have to make sure that the PCs have the correct gateway.
If this IP is the corresponding one, you should have a successful ping.
As both switches are Layer 2 switch and there is no VLAN or No VLAN routing is configured. Your PC1 or PC2 is having gateway IP of the Router's Interface. Then how is it working?
1. PC1 will be trying to Ping PC4. PC1 will found that this is an outside network with help of OR operation. Then PC1 will send the packet to the Default Gateway which is Router's interface IP address.
2. Here, the Router will receive the packet and check for Destination IP address in the Layer 3 header (I skipped packet flow process) and found as PC4 in the destination so it will lookup for the routing table (If CEF enabled then CEF entry) and found that this is directly connected network on other interfaces then it will forward the packet to the egress interface.
3. Packet will receive on PC4, process the request and the reply packet will send back to the gateway and it performs the same route lookup process and will send back to the PC1.
Here, As I mentioned that I skipped the many steps as Layer 2 header process, CEF activities, etc.