# VLANs, DHCP, and Inter-VLAN Routing Using Packet Tracer
## Introduction
VLANs are a fundamental part of enterprise networking. While they can seem complex at first, they offer a highly effective way to optimise and segment a network once understood. In this introduction, we’ll complete a series of tasks using the Cisco command line interface, working with managed switches and integrated services routers to build practical experience.
For an interactive experience, please download the following Packet Tracer Activity:
[Introduction to VLANs in Packet Tracer](https://codeberg.org/RDMillen/ComputingEducation/raw/branch/main/PacketTracerActivities/IntroToVLANs.pka)
The following instructions are mirrored within activity file, the below is for reference when working with physical hardware.
## Scenario
You are a network technician setting up a small segmented office network. Your objective is to:
- Create two VLANs: Admin (VLAN 10) and Students (VLAN 20)
- Configure a router to perform inter-VLAN routing using subinterfaces
- Set up DHCP so that devices receive IP addresses automatically
- Verify that devices on different VLANs can communicate
---
## Devices Required
- 1 x Cisco Router
- 1 x Cisco Managed Switch
- Client test machines
- 1 x Console Cable
---
## IP Addressing and VLAN Scheme
This is a common example of an IP addressing scheme with basic VLAN usage.
|VLAN|Subnet|Gateway|DHCP Range|
|---|---|---|---|
|10|192.168.10.0/24|192.168.10.1|192.168.10.11 – .254|
|20|192.168.20.0/24|192.168.20.1|192.168.20.11 – .254|
---
## Step 1: Configure the Cisco 3650 Switch
### Create VLANs
```shell
enable
configure terminal
vlan 10
name Admin
exit
vlan 20
name Students
exit
```
### Assign Ports to VLANs
Assume:
- GigabitEthernet1/0/1 and 1/0/2 are for VLAN 10
- GigabitEthernet1/0/3 and 1/0/4 are for VLAN 20
```shell
interface range GigabitEthernet1/0/1 - 2
switchport mode access
switchport access vlan 10
exit
interface range GigabitEthernet1/0/3 - 4
switchport mode access
switchport access vlan 20
exit
```
### Configure Trunk Port to Router
Assume GigabitEthernet1/0/24 connects to the router:
```shell
interface GigabitEthernet1/0/24
switchport mode trunk
exit
```
---
## Step 2: Configure the Cisco 1941 Router
### Remove IP from the Physical Interface
```shell
enable
configure terminal
interface GigabitEthernet0/0
no ip address
no shutdown
exit
```
### Create Subinterfaces for Each VLAN
```shell
interface GigabitEthernet0/0.10
encapsulation dot1Q 10
ip address 192.168.10.1 255.255.255.0
exit
interface GigabitEthernet0/0.20
encapsulation dot1Q 20
ip address 192.168.20.1 255.255.255.0
exit
```
---
## Step 3: Configure DHCP Services on the Router
```shell
ip dhcp excluded-address 192.168.10.1 192.168.10.10
ip dhcp excluded-address 192.168.20.1 192.168.20.10
ip dhcp pool VLAN10
network 192.168.10.0 255.255.255.0
default-router 192.168.10.1
exit
ip dhcp pool VLAN20
network 192.168.20.0 255.255.255.0
default-router 192.168.20.1
exit
```
---
## Step 4: Verify the Setup
From each PC:
* Set the PC to use DHCP
- Use the `ipconfig` command to check IP address allocation
- Confirm the default gateway matches the VLAN's router IP
- Use `ping` to:
- Reach the default gateway
- Communicate with another PC on the same VLAN
- Communicate with a PC on the other VLAN
From the router:
- Run `show ip interface brief` to confirm interfaces are up
- Run `show running-config` to review your setup