DHCP

DHCP (Dynamic Host Configuration Protocol) is a network protocol that automatically assigns IP configuration to devices on a network.

Instead of manually configuring every computer, DHCP provides network settings automatically when a device joins the network.

Typical information assigned by DHCP includes:

• IP address
• Subnet mask
• Default gateway
• DNS servers
• Lease time

Without DHCP, every device would need to be configured manually.

For example:

IP Address:
192.168.1.25

Subnet Mask:
255.255.255.0

Default Gateway:
192.168.1.1

DNS Server:
8.8.8.8

For a home with a few devices this may be manageable, but for schools, offices, or enterprises with hundreds or thousands of devices, manual configuration would be impractical.

DHCP automates this process.

When a device connects to a network, it typically performs four steps.

Client
   │
   │ 1. DHCP Discover
   ▼
DHCP Server
   ▲
   │ 2. DHCP Offer
   │
Client
   │
   │ 3. DHCP Request
   ▼
DHCP Server
   ▲
   │ 4. DHCP Acknowledgement (ACK)
   │
Client receives its IP configuration

This process is commonly called the DORA process:

• Discover
• Offer
• Request
• Acknowledgement

A laptop joins a Wi-Fi network.

The DHCP server assigns:

IP Address:
192.168.1.25

Subnet Mask:
255.255.255.0

Gateway:
192.168.1.1

DNS:
8.8.8.8

The user does not need to enter any of these values manually.

DHCP assigns addresses for a limited period called the lease time.

Example:

Lease Time

24 hours

Before the lease expires, the client usually requests to renew it.

If renewal succeeds, the device typically keeps the same IP address.

A DHCP server may be:

• A home Wi-Fi router
• A dedicated server
• A firewall
• A Layer 3 switch

In most home networks, the wireless router also acts as the DHCP server.

A device may use either:

Assigned automatically by DHCP.

Suitable for:

• Computers
• Smartphones
• Tablets
• Guest devices

Configured manually.

Often used for:

• Servers
• Printers
• Network cameras
• Firewalls

Many DHCP servers support reservations.

A reservation means a particular device always receives the same IP address.

Example:

Printer

MAC Address

00:1A:2B:3C:4D:5E

↓

Always receives

192.168.1.100

This combines automatic management with predictable addressing.

IPv6 also supports DHCP.

However, IPv6 devices may obtain network information through:

• Router Advertisements (RA)
• DHCPv6
• Both

Unlike IPv4, DHCP is not always required in IPv6 networks.

If no DHCP server is available, a device may:

• Fail to obtain an IP address.
• Assign itself a link-local address.

Example (Windows):

169.254.x.x

Such an address allows limited communication within the local network but usually does not provide Internet access.

Current Telenegar Internet tools do not directly display DHCP information because DHCP operates only within the local network.

However, understanding DHCP helps explain why:

• A device receives its IP address automatically.
• Local network configuration changes.
• Internet access may fail after connecting to a network.

• DHCP changes the MAC address.
  • False. DHCP assigns IP configuration, not hardware addresses.

• DHCP always assigns a different IP address.
  • False. A device often receives the same address repeatedly, especially if its lease is renewed.

• Only large organizations use DHCP.
  • False. Almost every home router includes a DHCP server.

• IP Addresses
• Default Gateway
• MAC Address
• Subnetting
• Network Address Translation (NAT)

dhcp ip networking ipv4 ipv6 dora