Packet Tracer Lab: Two Networks With One Router

This lab helped me understand why different subnets need a router to communicate.

Topology

I used two PCs, two switches, and one router. LAN A used 192.168.10.0/24. LAN B used 192.168.20.0/24.

The point of the topology is to make two separate networks. If both PCs are in the same subnet, routing is not being tested. By using two different subnets, I can see why the router is required.

Configuration idea

Each router interface gets an IP address in its connected subnet. Each PC uses the router interface in its subnet as the default gateway.

For example, the router interface connected to LAN A might be 192.168.10.1. PC A might be 192.168.10.10 with gateway 192.168.10.1. LAN B follows the same idea with 192.168.20.1 as the gateway.

Testing

First I pinged within the same LAN. Then I pinged across LANs. If cross-network ping failed, I checked IP addresses, gateway settings, interface status, and subnet masks.

Troubleshooting order

Check whether each PC can ping its own gateway.
Check whether router interfaces are up.
Check IP addresses and subnet masks.
Check whether each PC has the correct default gateway.
Try cross-LAN ping again and document the result.

Why this lab matters

This small lab teaches the foundation of routing. Larger networks still depend on the same idea: devices send remote traffic to a router, and routers move packets between networks.

Lesson learned

Routing is easier to understand when I draw the topology and label every interface. A missing gateway or wrong subnet mask can break the whole lab.