ArunNetworkingPro
🧱

Build a virtual network

All the routers, none of the electricity bill.

Cisco Packet Tracer gives you a drawer full of routers, switches and PCs for free. In this lab you'll build two separate networks and make a router join them together, which is the whole idea of routing in one picture.

BeginnerA weekendPacket Tracer
PC0PC1switchrouterswitchPC2192.168.1.0/24192.168.2.0/24the matchmaker

🧰 What you need

Let's build it

1

Place the devices

From the bottom toolbar, drag out one 2911 router, two 2960 switches and three PCs.

2

Cable them

Use the lightning-bolt (automatic) cable. Connect PC0 and PC1 to Switch0, PC2 to Switch1, then Switch0 to the router's GigabitEthernet0/0 and Switch1 to GigabitEthernet0/1. The router links show red: its ports are off until you turn them on.

3

Configure the router

Click the router → CLI tab, answer no to the setup wizard, and type:

enable
configure terminal
interface g0/0
 ip address 192.168.1.1 255.255.255.0
 no shutdown
interface g0/1
 ip address 192.168.2.1 255.255.255.0
 no shutdown
end

The links turn green.

4

Address the PCs

Click each PC → Desktop → IP Configuration:

  • PC0: 192.168.1.10, mask 255.255.255.0, gateway 192.168.1.1
  • PC1: 192.168.1.11, same mask, gateway 192.168.1.1
  • PC2: 192.168.2.10, same mask, gateway 192.168.2.1
5

Ping across the router

On PC0 → Desktop → Command Prompt:

ping 192.168.2.10

The first ping may time out while the devices learn each other's addresses. The rest succeed.

6

Watch it in slow motion

Switch to Simulation mode (bottom right), run the ping again and press Play. You can watch each packet hop from PC to switch to router to switch to PC, and click any packet to see what's inside.

✅ How you know it worked

PC0 can ping PC1 (same network, no router needed) and PC2 (different network, through the router).

💥 Break it on purpose

On PC2, delete the default gateway and ping PC0 again. It fails, even though PC2's address and cable are perfect: it knows how to reach its own network, but has no idea where to send anything else. Put the gateway back and it works. This is one of the most common real-world faults there is.

🧠 What's really going on

A switch connects devices on the same network. To reach a different network, a device sends its traffic to its default gateway, the router, which looks up the destination in its routing table and forwards it out of the right interface. Every connection you've ever made across the internet is this same idea, repeated across many routers.

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