DHCP (Dynamic Host Configuration Protocol)


In a network all the Layer 3 devices need to have an IP address. We can give these IP addresses manually one by one or dynamically and automatically with IP address allocation mechanisms, DHCP (Dynamic Host Configuration Protocol. Here, beside IP addresses, we can configure the allocation of other IP related configurations with DHCP.

Table of Contents

DHCP IP Allocation Mechanisms

DHCP (Dynamic Host Configuration Protocol) has three IP Allocation Mechanisms. These are:

• Dynamic
• Automatic
• Manual

The first one is Dynamic IP Allocation. Dynamic IP Allocation, allocates IP addresses from a predefined Pool and can be cancelled.

Secondly, Automatic IP Allocation. In Automatic IP Allocation, allocates IP addresses from a predefined Pool too, but this time can not be cancelled.

Thirdly, Manuel IP Allocation. In Manuel IP Allocation, allocates IP addresses according to request of host and this is a range out of the pool.

If, DHCP assigns IP addresses from its predefined IP Pools dynamically, it leases these IP addresses for a short time to the DHCP Client. And DHCP Client uses this IP address until it expires. Before the expiration, DHCP Client request renewal or another IP address.

DHCP Devices and Roles

In DHCP (Dynamic Host Configuration Protocol) terminology, there are different devices and roles. These devices and roles are:

• DHCP Server
• DHCP Client
• DHCP Relay Agent

First of all, we do the configurations on DHCP Server. These configurations are, all the configurations like IP Address Pools, Gateway Address etc. It is the mechanims that has the IP pools and provides IP addresses to the other nodes.


Secondly, DHCP Client is the other hosts here. The devices that need IP in a network is the DHCP Client for DHCP Server. To be so, it is also need to be configured to use this DHCP Server.

Lesson tags: DHCP
Back to: CCNA > DHCP and DNS

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