Build a Routed Multi-Network Lab

Design and wire a 3-subnet company network using Cisco Packet Tracer.

Introduction

30 Second Summary

Every time you send a message to a coworker in another department, your data crosses switches, routers, and subnets to get there. Understanding how that journey works is the foundation of every networking career.

In this project, you will build a company network from scratch in Cisco Packet Tracer, connecting three departments with their own subnets and watching packets travel hop-by-hop through your network.

What You'll Build

A routed multi-subnet network for a fictional company called TechCorp, with 6 PCs, 3 switches, and a central router connecting Sales, Engineering, and Management departments.

By the end of this project, you'll have:

  • A working 3-subnet network with full end-to-end connectivity between departments.
  • Hands-on experience configuring router interfaces and assigning IP addresses using Cisco IOS CLI commands.
  • A visual understanding of how packets travel hop-by-hop through switches and routers using Simulation Mode.
  • Secret Mission: Add DHCP so devices get their IP addresses automatically instead of manual configuration.

Are there any prerequisites?

You need a free Cisco Networking Academy (NetAcad) account to download Packet Tracer and log in on first launch. If you don't have one yet, you can create it at netacad.com in under a minute.

Build the Physical Network Topology

Your Packet Tracer workspace is set up and ready. Now it is time to build the physical network that connects TechCorp's three departments.

Every network starts with a physical topology. This is the layout of real devices and cables that carry data between machines. In this step, you will place a central router, three department switches, and six PCs on the workspace, then wire them all together.

In this step, get ready to:
  • Place the router and switches on the workspace.
  • Add PCs for each department.
  • Wire every device together with cables.
Place the network devices

TechCorp's network needs a central router to move traffic between departments, and one switch per department to connect the local PCs together.

Why a router and switches?

A switch connects devices within the same network (like PCs in the Sales team). A router connects different networks together so that Sales can talk to Engineering.

Without the router, each department would be isolated on its own island.

  • In the bottom device panel, click Network Devices.
  • Click Routers.
  • Drag a 2911 router to the center of your workspace.
  • In the bottom device panel, click Network Devices again, then click Switches.
  • Drag a 2960 switch to the left of the router.
  • Drag a second 2960 switch to the right of the router.
  • Drag a third 2960 switch below the router.

Now label each device so you can identify them later.

  • Click on the router. In the config panel that appears, change its display name to Router-Main.
  • Click on the left switch and name it Sales-SW.
  • Click on the right switch and name it Engineering-SW.
  • Click on the bottom switch and name it Management-SW.

Your workspace should now show four labeled devices arranged with the router in the middle and three switches around it.

Don't see the 2911 or 2960 in the list?

Make sure you clicked Network Devices first (not End Devices), then selected the correct subcategory (Routers or Switches). The 2911 and 2960 appear in the default device list.

help me find the 2911 router and 2960 switch in Packet Tracer's device panel

Place the end devices (PCs)

Each department has two PCs that represent the employees' workstations. You will place two PCs near each switch to show which department they belong to.

  • In the bottom panel, click End Devices.
  • Drag a PC near the Sales-SW switch.
  • Click on it and name it PC1.
  • Drag a second PC near Sales-SW and name it PC2.
  • Drag a PC near the Engineering-SW switch and name it PC3.
  • Drag another PC near Engineering-SW and name it PC4.
  • Drag a PC near the Management-SW switch and name it PC5.
  • Drag another PC near Management-SW and name it PC6.

You should now see 6 PCs on the workspace, paired up near their respective switches.

Connect everything with cables

Devices on a network communicate over physical cables. You need to select the right cable type and plug each end into the correct port on each device.

Why Copper Straight-Through?

A Copper Straight-Through cable connects different types of devices together (PC to switch, switch to router). A crossover cable connects same-type devices (switch to switch, router to router).

Since every connection in this network links a different device type, Copper Straight-Through is correct for all of them.

  • In the bottom panel, click Connections.
  • Select the Copper Straight-Through cable (the solid black line icon).

Now connect the Sales PCs to their switch.

  • Click on PC1 and select FastEthernet0.
  • Click on Sales-SW and select FastEthernet0/1.
  • Click on PC2 and select FastEthernet0.
  • Click on Sales-SW and select FastEthernet0/2.

Connect the Engineering PCs to their switch.

  • Click on PC3 and select FastEthernet0.
  • Click on Engineering-SW and select FastEthernet0/1.
  • Click on PC4 and select FastEthernet0.
  • Click on Engineering-SW and select FastEthernet0/2.

Connect the Management PCs to their switch.

  • Click on PC5 and select FastEthernet0.
  • Click on Management-SW and select FastEthernet0/1.
  • Click on PC6 and select FastEthernet0.
  • Click on Management-SW and select FastEthernet0/2.

Finally, connect each switch to the central router.

  • Click on Sales-SW and select GigabitEthernet0/1.
  • Click on Router-Main and select GigabitEthernet0/0.
  • Click on Engineering-SW and select GigabitEthernet0/1.
  • Click on Router-Main and select GigabitEthernet0/1.
  • Click on Management-SW and select GigabitEthernet0/1.
  • Click on Router-Main and select GigabitEthernet0/2.
  • Save your file by pressing Ctrl+S.

Look at the link light indicators on each cable. The lights between PCs and switches should be green (active). The lights between switches and the router should be red or orange.

Why are the router links red?

Router interfaces start in a "shutdown" state by default. The physical cable is plugged in, but the interface is administratively disabled. You will bring these interfaces up in a later step when you configure IP addressing on the router.

Switches do not have this problem because their ports are active by default.

Seeing red lights on PC-to-switch links too?

Double-check you used a Copper Straight-Through cable, not a Crossover or Console cable. Delete the incorrect cable by clicking on it and pressing Delete, then reconnect with the correct cable type.

Also verify you connected to the correct port. PCs use FastEthernet0 (not RS-232 or USB). Switches should use FastEthernet0/1 or FastEthernet0/2 for PCs.

help me troubleshoot red link lights between my PCs and switches in Packet Tracer

Your physical network is built. Every device is placed and cabled. Next up, you will give each PC an IP address so they know where to send data.

Configure IP Addressing on All PCs

Your physical network is wired up, but right now every device is like a house without a street address. No device knows how to find any other device on the network.

In this step, you will assign IP addresses to each PC using a planned subnetting scheme. Each department gets its own subnet so devices can be logically grouped and routed between.

In this step, get ready to:
  • Plan an IP addressing scheme with three separate subnets.
  • Configure static IP addresses, subnet masks, and default gateways on all 6 PCs.
Plan the addressing scheme

Before touching any device, you need a plan. Each department will live on its own subnet, meaning each group of PCs uses a different range of IP addresses.

Here is the addressing scheme for TechCorp:

  • Sales: 192.168.1.0/24 (subnet mask 255.255.255.0).
  • Engineering: 192.168.2.0/24 (subnet mask 255.255.255.0).
  • Management: 192.168.3.0/24 (subnet mask 255.255.255.0).

Each subnet's default gateway will be the router interface at the .1 address (e.g. 192.168.1.1 for Sales). The gateway is the door that packets use to leave a subnet and reach other subnets.

Why does each department need its own subnet?

Subnets divide a larger network into smaller, manageable sections. Devices on the same subnet can talk directly through their switch. Devices on different subnets must go through the router.

This separation improves security (you can control which departments talk to each other) and reduces unnecessary traffic on each segment.

Configure Sales PCs (PC1 and PC2)

You will configure each PC through the graphical IP Configuration panel inside Packet Tracer. This is the same as opening network settings on a real computer and typing in a static IP.

  • Click on PC1 in your workspace to open its configuration window.
  • Click the Desktop tab at the top of the window.
  • Click IP Configuration.
  • In the IPv4 Address field, enter 192.168.1.10.
  • In the Subnet Mask field, enter 255.255.255.0.
  • In the Default Gateway field, enter 192.168.1.1.
  • Close PC1's window by clicking the X in the top-right corner.

Now repeat the process for PC2.

  • Click on PC2 in your workspace.
  • Click the Desktop tab.
  • Click IP Configuration.
  • In the IPv4 Address field, enter 192.168.1.11.
  • In the Subnet Mask field, enter 255.255.255.0.
  • In the Default Gateway field, enter 192.168.1.1.
  • Close PC2's window.

What do these three fields mean?

  • IPv4 Address is the unique identity of this device on its subnet.
  • Subnet Mask tells the PC which portion of the address identifies the network vs. the individual host.
  • Default Gateway is the router interface address. When the PC needs to reach a different subnet, it sends the packet here.

Subnet Mask auto-filled to something unexpected?

Packet Tracer sometimes auto-fills the subnet mask based on the IP class. If it shows something other than 255.255.255.0, simply clear the field and type 255.255.255.0 manually.

help me fix the subnet mask on my PC in Packet Tracer

Configure Engineering and Management PCs

The process is identical for the remaining four PCs. The only difference is that each department uses a different subnet.

  • Click on PC3 in your workspace.
  • Click the Desktop tab, then click IP Configuration.
  • In the IPv4 Address field, enter 192.168.2.10.
  • In the Subnet Mask field, enter 255.255.255.0.
  • In the Default Gateway field, enter 192.168.2.1.
  • Close PC3's window.
  • Click on PC4 in your workspace.
  • Click the Desktop tab, then click IP Configuration.
  • In the IPv4 Address field, enter 192.168.2.11.
  • In the Subnet Mask field, enter 255.255.255.0.
  • In the Default Gateway field, enter 192.168.2.1.
  • Close PC4's window.
  • Click on PC5 in your workspace.
  • Click the Desktop tab, then click IP Configuration.
  • In the IPv4 Address field, enter 192.168.3.10.
  • In the Subnet Mask field, enter 255.255.255.0.
  • In the Default Gateway field, enter 192.168.3.1.
  • Close PC5's window.
  • Click on PC6 in your workspace.
  • Click the Desktop tab, then click IP Configuration.
  • In the IPv4 Address field, enter 192.168.3.11.
  • In the Subnet Mask field, enter 255.255.255.0.
  • In the Default Gateway field, enter 192.168.3.1.
  • Close PC6's window.
  • Save your topology by pressing Ctrl+S.
  • Verify your work by clicking on any PC (e.g. PC5), clicking the Desktop tab, clicking IP Configuration, and confirming the IP address, subnet mask, and gateway fields are filled in correctly.

✔️ Awesome, I've got everything!

Great. Make sure you have saved your topology file before moving on.

ⓧ I'd like to double check the full IP table

Here is the complete addressing table for all 6 PCs. Every PC should match these values exactly.

PC1: IP 192.168.1.10 | Mask 255.255.255.0 | Gateway 192.168.1.1
PC2: IP 192.168.1.11 | Mask 255.255.255.0 | Gateway 192.168.1.1
PC3: IP 192.168.2.10 | Mask 255.255.255.0 | Gateway 192.168.2.1
PC4: IP 192.168.2.11 | Mask 255.255.255.0 | Gateway 192.168.2.1
PC5: IP 192.168.3.10 | Mask 255.255.255.0 | Gateway 192.168.3.1
PC6: IP 192.168.3.11 | Mask 255.255.255.0 | Gateway 192.168.3.1

IP Configuration fields are greyed out?

Make sure the Static radio button is selected at the top of the IP Configuration panel. If DHCP is selected, the fields will be read-only because the PC is waiting for an automatic address.

help me troubleshoot IP Configuration in Packet Tracer

Every PC now has a unique address and knows where to send packets destined for other subnets. Next up, you will configure the router so it can actually accept and forward those packets between departments.

Configure the Router

Your PCs all have IP addresses, but they still can't talk to devices on other subnets. That's because the router sitting in the middle hasn't been told what IP addresses belong to its interfaces.

In this step, you'll bring the router to life using Cisco IOS CLI commands. You'll assign an IP address to each of the router's three interfaces and activate them so traffic can flow between subnets.

In this step, get ready to:
  • Access the router's command line interface.
  • Configure IP addresses on all three GigabitEthernet interfaces.
  • Verify that every interface is up and routing traffic.
Access the router CLI

Before you can configure the router, you need to enter its command line. Packet Tracer gives you direct CLI access by clicking on the device.

  • Click on Router-Main in your topology.
  • Click the CLI tab in the window that appears.
  • Press Enter to get a command prompt.
  • Enter privileged exec mode and global configuration mode by typing the following commands:
enable
configure terminal
hostname Router-Main

What do these commands do?

  • enable enters privileged EXEC mode, giving you full access to configuration commands.
  • configure terminal enters global configuration mode, where you can change the router's settings.
  • hostname Router-Main sets the router's name so you can identify it in the CLI prompt.
Configure all three interfaces

Each router interface connects to one of TechCorp's three department subnets. You need to assign the correct IP address and activate each interface with no shutdown.

  • Type the following commands into the router CLI to configure all three GigabitEthernet interfaces:
interface GigabitEthernet0/0
 ip address 192.168.1.1 255.255.255.0
 no shutdown
exit

interface GigabitEthernet0/1
 ip address 192.168.2.1 255.255.255.0
 no shutdown
exit

interface GigabitEthernet0/2
 ip address 192.168.3.1 255.255.255.0
 no shutdown
exit
end

What does this configuration do?

Each block follows the same pattern. Here's what each command does:

  • interface GigabitEthernet0/0 selects which physical port you're configuring.
  • ip address 192.168.1.1 255.255.255.0 assigns an IP address and subnet mask to that interface. This is the default gateway address your PCs are already pointing to.
  • no shutdown activates the interface. Router interfaces are shut down by default.
  • exit returns you to global configuration mode so you can configure the next interface.
  • end exits configuration mode entirely and returns to privileged EXEC mode.

Since all three subnets are directly connected to this router, it automatically knows how to reach each one. No static or dynamic routing configuration is needed.

Links still showing red or orange?

  • Make sure you typed no shutdown on each interface. Without it, the interface stays administratively down.
  • Check that your IP addresses match exactly. A typo like 192.168.1.11 instead of 192.168.1.1 assigns the wrong address.
  • Confirm you typed exit after each interface block before starting the next one.

ask me for help troubleshooting my router interface configuration

Verify the router configuration

Now that all interfaces are configured, you can confirm they're active with a single verification command.

  • Type this command in the router CLI:
show ip interface brief

You should see a table with all three GigabitEthernet interfaces listed. Each one should show its assigned IP address, with Status as up and Protocol as up.

What does up/up mean?

The Status column shows the physical layer (Layer 1) state of the interface. The Protocol column shows the data link layer (Layer 2) state. When both say up, the interface is physically connected and ready to pass traffic.

  • Look at your topology canvas. The cable link indicators between each switch and the router should now be green.
  • Save your file by pressing Ctrl+S.

Seeing down/down on an interface?

  • Verify the cable is connected to the correct port. GigabitEthernet0/0 should connect to Sales-SW, GigabitEthernet0/1 to Engineering-SW, and GigabitEthernet0/2 to Management-SW.
  • If Status shows administratively down, you missed the no shutdown command on that interface. Re-enter configuration mode and apply it.

help me debug my show ip interface brief output

✔️ Awesome, I've got everything!

Great. Make sure you've saved your file with Ctrl+S.

ⓧ I'd like to double check the full code

Here's everything you typed into the router CLI during this step:

enable
configure terminal
hostname Router-Main

interface GigabitEthernet0/0
 ip address 192.168.1.1 255.255.255.0
 no shutdown
exit

interface GigabitEthernet0/1
 ip address 192.168.2.1 255.255.255.0
 no shutdown
exit

interface GigabitEthernet0/2
 ip address 192.168.3.1 255.255.255.0
 no shutdown
exit

end

Your router is now the traffic controller connecting all three departments. Next up, you'll prove it works by pinging between subnets and watching a packet travel through your network in Simulation Mode.

Test Connectivity and Simulate Packet Flow

Your router is fully configured and all three interfaces are up. The physical connections are live, which means your three department subnets should be able to talk to each other.

Now comes the moment of truth. You will send actual data between departments and then use Simulation Mode to watch exactly how each packet hops through your network.

In this step, get ready to:
  • Test connectivity within the same subnet using ping.
  • Test cross-subnet connectivity through the router.
  • Visualize packet flow step-by-step using Simulation Mode.
Test within the same subnet

Before testing across subnets, confirm that devices on the same subnet can reach each other. This verifies your cables and switch connections are working correctly.

  • Click on PC1 in your topology.
  • Click the Desktop tab at the top of the PC1 window.
  • Click Command Prompt to open a simulated terminal.
  • Ping PC2 (which is on the same Sales subnet) by typing this command:
ping 192.168.1.11

You should see four reply lines with 0% packet loss. This confirms the Sales subnet is working.

Not getting replies?

  • Double-check that PC2's IP address is 192.168.1.11 with subnet mask 255.255.255.0. A typo in either field will break connectivity.
  • Make sure the cable between PC2 and Sales-SW shows green link lights on both ends. If it shows red or orange, delete the cable and reconnect it.

Help me troubleshoot why my same-subnet ping is failing in Packet Tracer.

Test across subnets

Same-subnet communication only proves the switch is working. The real test is whether your router can forward traffic between different subnets.

  • In PC1's Command Prompt (still open from the previous test), ping PC3 in the Engineering subnet by typing:
ping 192.168.2.10
  • Now ping PC5 in the Management subnet:
ping 192.168.3.10

Both pings should return replies with 0% packet loss. This proves your router is forwarding packets between all three subnets.

Why does cross-subnet ping work without static routes?

All three subnets are directly connected to Router-Main's interfaces. The router automatically knows how to reach each subnet because it has an interface sitting on that network.

Static or dynamic routing protocols are only needed when a destination subnet is NOT directly connected to the router.

  • Now test the reverse direction. Click on PC5 in your topology.
  • Click the Desktop tab, then click Command Prompt.
  • Ping PC1 from the Management subnet by typing:
ping 192.168.1.10

You should see replies with 0% packet loss. Traffic flows in both directions across your network.

Cross-subnet pings failing?

  • Check the default gateway on the failing PC. It must point to the router's interface on that subnet (e.g., PC1's gateway must be 192.168.1.1, PC3's must be 192.168.2.1, PC5's must be 192.168.3.1).
  • Verify the router interfaces are still up. Click Router-Main, go to the CLI tab, and type show ip interface brief. All three GigabitEthernet interfaces should show "up" in both the Status and Protocol columns.
  • If you see "Request timed out" on the first ping but replies on the second attempt, that is normal. The first ping sometimes fails while the network learns MAC addresses (ARP resolution).

Help me figure out why my cross-subnet ping is not working in Packet Tracer.

Use Simulation Mode to visualize packet flow

Seeing a successful ping tells you the network works. Simulation Mode lets you watch exactly how a packet travels hop-by-hop through switches and the router.

  • In the bottom-right corner of the Packet Tracer window, click Simulation to switch from Realtime to Simulation mode.

What is Simulation Mode?

In Realtime mode, packets fly through the network instantly (just like a real network). Simulation Mode pauses time so you can step through each packet hop one at a time.

This is one of Packet Tracer's most powerful learning features. It makes the invisible process of routing visible.

  • In the Event List Filters panel, make sure only ICMP is checked. This filters out background noise and shows only ping packets.
  • Click on PC1 in your topology.
  • Go to the Desktop tab and open Command Prompt.
  • Send a ping to PC5 in the Management subnet by typing:
ping 192.168.3.10
  • Click the Capture/Forward button repeatedly to advance the packet one hop at a time.

Watch the packet move through the network. You should see it follow this path:

  • PC1 sends the packet to Sales-SW.
  • Sales-SW forwards it to Router-Main on GigabitEthernet0/0.
  • Router-Main routes the packet out GigabitEthernet0/2 toward Management.
  • Management-SW forwards it to PC5.
  • PC5 sends a reply back along the reverse path.
  • Click on any envelope icon on the topology to inspect the packet details at that hop. You can see the source and destination IP addresses, the layer information, and which interface the packet enters and exits.

What am I seeing at each hop?

At PC1, the packet is created with a source IP of 192.168.1.10 and a destination of 192.168.3.10. PC1 knows this destination is on a different subnet, so it sends the packet to its default gateway.

At the router, the device checks its routing table, finds that 192.168.3.0/24 is directly connected to GigabitEthernet0/2, and forwards the packet out that interface. This is the core job of a router.

  • Save your project file by pressing Ctrl+S.

Packet disappearing mid-path?

  • If the packet disappears at the router, check that the outgoing interface (GigabitEthernet0/2 for Management-bound traffic) is in the "up/up" state.
  • If you see a red X on the packet, it means a device dropped it. Click the X to see which layer caused the drop and why.
  • Make sure you unchecked all protocols except ICMP in the Event List Filters. Other protocol traffic can clutter the simulation and make it hard to follow your ping.

Help me understand why my packet is being dropped in Simulation Mode.

Secret mission

Add DHCP So Devices Get IPs Automatically

Right now, every PC in your network has a manually typed IP address. In a real company with hundreds of devices, that would be impossible to maintain. Configure the router as a DHCP server so new devices get their network settings automatically the moment they connect.

Clean Up Your Resources

Clean Up Your Resources

This project runs entirely locally using Cisco Packet Tracer, so there are no ongoing costs. Decide whether to keep your resources as they are, or delete them entirely.

Resources you used:

  • Cisco Packet Tracer (installed application).
  • TechCorp-Network.pkt file (your saved project topology).

Keep everything running

No action needed. Choose this if you want to keep experimenting with your TechCorp network or build more complex topologies in Packet Tracer.

  • Your TechCorp-Network.pkt file stays wherever you saved it.
  • Cisco Packet Tracer remains installed and ready for future labs.

Pause - I'll come back to this later

Since Packet Tracer is a local application with no running processes in the background, there is nothing to pause. Your project file is already saved and waiting for you.

  • Close Cisco Packet Tracer if it is still open.
  • Your TechCorp-Network.pkt file will be exactly as you left it when you reopen it.

Delete - I don't want to use this again

Remove your project file and uninstall Cisco Packet Tracer from your machine.

  • Delete your TechCorp-Network.pkt file from the folder where you saved it.
  • To uninstall Cisco Packet Tracer, open Settings.
  • Select Apps, then Installed apps.
  • Search for Cisco Packet Tracer, click the three-dot menu next to it, and select Uninstall.
  • Follow the prompts to complete the removal.

Nice Work!

Nice Work!

You just built a fully routed multi-subnet company network from scratch using Cisco Packet Tracer. Three departments, three subnets, one central router, and full end-to-end connectivity between every device.

You've learned how to:

  • Design and build a 3-subnet network topology with proper cabling between PCs, switches, and a central router.
  • Configure router interfaces using Cisco IOS CLI commands to enable routing between departments.
  • Visualize packet flow hop-by-hop using Simulation Mode to understand how data travels through switches and routers.
  • Secret Mission: Configured DHCP pools on the router to automatically assign IP addresses to all devices instead of manual configuration.

Ready to quiz yourself?