DHCP Dynamic Host Configuration Protocol practical in cisco packet tracer

🌐 DHCP (Dynamic Host Configuration Protocol)

DHCP is a network protocol used to automatically assign IP configuration to clients in a network.

This is used in:

• Offices
• Companies
• Schools
• WiFi routers
• ISPs
• Enterprise networks

Almost every modern network uses DHCP.

🎯 What DHCP Does

Instead of manually assigning IP addresses to every PC:

❌ Manual:

PC1 = 192.168.1.10
PC2 = 192.168.1.11
PC3 = 192.168.1.12

✅ DHCP automatically gives:

• IP Address
• Subnet Mask
• Default Gateway
• DNS Server

🔥 Real-Life Example

When you connect:

Mobile to WiFi

Laptop to office LAN

👉 Router automatically gives IP

That is DHCP.

🎯 What You Will Learn

• ✔ Automatic IP allocation
• ✔ DHCP pool creation
• ✔ Default gateway assignment
• ✔ DNS assignment
• ✔ Lease process
• ✔ Enterprise networking basics

🧪 Practical Topology

In Cisco Packet Tracer create:

PC0 ----\
PC1 ----- Switch ---- Router
PC2 ----/

🌐 IP Plan

🔌 Wiring

PCs → Switch

Use:

Copper Straight-Through

Switch → Router

Use:

Copper Straight-Through

⚙️ Step 1: Configure Router Interface

On router:

enable
configure terminal

interface g0/0
ip address 192.168.1.1 255.255.255.0
no shutdown

🔥 Step 2: Configure DHCP Service

ip dhcp pool OFFICE

👉 Creates DHCP pool named OFFICE

Configure Network

network 192.168.1.0 255.255.255.0

Configure Default Gateway

default-router 192.168.1.1

Configure DNS

dns-server 8.8.8.8

🔥 Full DHCP Configuration

enable
configure terminal

interface g0/0
ip address 192.168.1.1 255.255.255.0
no shutdown

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

🔥 Step 3: Exclude Router IP

VERY IMPORTANT

ip dhcp excluded-address 192.168.1.1

🧠 Why?

👉 Prevents DHCP from assigning router IP to PCs.

🔥 Step 4: Configure PCs

On every PC:

Desktop → IP Configuration

Select:

DHCP

🎯 Result

PC automatically gets:

🧪 Step 5: Verify

From PC:

ipconfig

You’ll see DHCP-assigned IP.

🧪 Step 6: Test Connectivity

ping 192.168.1.1

✔ Success

🔍 DHCP Process (VERY IMPORTANT)

DORA Process

🧠 How It Works

• 1️⃣ PC broadcasts DHCP Discover
• 2️⃣ Router replies DHCP Offer
• 3️⃣ PC sends Request
• 4️⃣ Router sends Acknowledgement

✔ IP assigned

🔥 Verification Commands

On router:

show ip dhcp binding

👉 Shows assigned IPs

show ip dhcp pool

👉 Shows DHCP pool details

🧠 Important Interview Questions

❓ What port does DHCP use?

UDP 67 & 68

❓ What is APIPA?

If DHCP fails:

169.254.x.x

❓ Why exclude addresses?

Prevent important IP assignment conflicts.

❓ What is lease time?

Duration client can use IP.

🔥 Common Mistakes

🎯 What You Learned

• ✔ Automatic IP assignment
• ✔ DHCP pool
• ✔ DORA process
• ✔ Enterprise IP management
• ✔ Router as DHCP server

Disclaimer