Hands-On Lab: Setting Up a Basic Office Network (3 Switches, 1 Router)

In this first post of Network Lab Series, I’ll show how I set up a basic local network using a Cisco 3660 router, 3 switches, and 3 virtual PCs. The router provides DHCP pools for three different subnets, simulating departments or different network segments. This lab is a practical intro to DHCP configuration, interface setup, and basic routing on Cisco hardware.

Lab Overview

• Router: Cisco 3660 with 3 FastEthernet interfaces

• Switches: 3 switches connected to different router interfaces

• Hosts: 3 Virtual PCs connected to switches

• Goal: Enable DHCP for 3 subnets, basic IP addressing

Router Interface and DHCP Setup

I configured three FastEthernet interfaces on the router with IP addresses and brought them up:

interface FastEthernet0/0
 ip address 192.168.1.1 255.255.255.0
 no shutdown

interface FastEthernet0/1
 ip address 192.168.10.1 255.255.255.0
 no shutdown

interface FastEthernet1/0
 ip address 192.168.20.1 255.255.255.0
 no shutdown

Excluded router IPs from DHCP pools:

ip dhcp excluded-address 192.168.1.1
ip dhcp excluded-address 192.168.10.1
ip dhcp excluded-address 192.168.20.1

Configured three DHCP pools for each subnet, why not a sinlge pool for all?

1. Subnet Segmentation & IP Management
   Each DHCP pool serves a specific subnet, ensuring devices get IPs from the correct IP range for their department or VLAN. This avoids IP conflicts and keeps addressing organized.

2. Simplified Troubleshooting
   When IP addresses are clearly segmented, it’s easier to identify where issues are occurring based on IP range.

ip dhcp pool HR
 network 192.168.1.0 255.255.255.0
 default-router 192.168.1.1
 dns-server 8.8.8.8

ip dhcp pool Eng
 network 192.168.10.0 255.255.255.0
 default-router 192.168.10.1
 dns-server 8.8.8.8

ip dhcp pool Sales
 network 192.168.20.0 255.255.255.0
 default-router 192.168.20.1
 dns-server 8.8.8.8

Verifying Configuration

Show IP interface brief confirms interfaces are up with correct IPs:

show ip interface brief

FastEthernet0/0     192.168.1.1     up
FastEthernet0/1     192.168.10.1    up
FastEthernet1/0     192.168.20.1    up

Switch and Host Setup

The 3 switches connect to router interfaces corresponding to their subnet. The three virtual PCs were assigned IPs via DHCP from the router. All devices are able to communicate locally.

On every PC enable the VPCs to request IP address from the DHCP server

PC> dhcp
DDORA IP 192.168.10.2/24 GW 192.168.10.1

Testing Connectivity

After configuring the router interfaces and DHCP pools, it’s important to verify that the network is working as expected. Here’s how I tested connectivity:

1. Ping from Router to Hosts

I pinged the IP addresses assigned to the virtual PCs to confirm they received IPs from the correct DHCP pools and that interfaces are reachable.

R1# ping 192.168.1.2
!!!!!  
Success rate is 100 percent (5/5)

R1# ping 192.168.10.1
!!!!!  
Success rate is 100 percent (5/5)

R1# ping 192.168.10.2
!!!!!  
Success rate is 100 percent (5/5)

2. Ping from Host to Router Interfaces

From the virtual PCs, I pinged the router’s gateway IP address in their subnet to check that the hosts can communicate with the router

PC1> ping 192.168.1.1
Reply from 192.168.1.1: bytes=84 time=15ms TTL=255

PC1> ping 192.168.10.1
Reply from 192.168.10.1: bytes=84 time=18ms TTL=255

3. Host to Host (Within and Across Subnets)

PC1 was able to ping other hosts on the same subnet and also across the different subnets, demonstrating local routing and DHCP working correctly:

PC1> ping 192.168.1.1   # Router gateway for HR subnet  
PC1> ping 192.168.10.2  # Host in Engineering subnet  
PC1> ping 192.168.20.2  # Host in Sales subnet

Summary

The successful pings in all directions confirm:

• DHCP pools are correctly handing out IP addresses

• Router interfaces are configured and reachable

• Hosts can communicate locally within and across subnets

Thanks for Reading!

I hope you found this simple network lab helpful and easy to follow. Setting up DHCP pools and getting devices talking is a great first step toward mastering real-world networking.

If you’re learning along with me, keep experimenting and don’t be afraid to make mistakes, that’s how you get better! Stay tuned for the next posts where we’ll explore routing between subnets, VLANs, and more advanced setups.

Got questions or want to share your own labs? Drop a comment, I’d love to hear from you!