What is DHCP?


In a network all the Layer 3 devices need to have an IP address. These IP addresses can be given manually one by one or dynamically and automatically with IP address allocation mechanim, DHCP (Dynamic Host Configuration Protocol. Here, beside IP addresses, other IP related allocation is also done with DHCP.

DHCP has three IP Allocation Mechanisms. These are:

• Dynamic
• Automatic
• Manual

In Dynamic IP Allocation, IP address is assigned from a predefined Pool and can be cancelled.

In Automatic IP Allocation, again, IP address is assigned from a predefined Pool, but this time can not be cancelled.

In Manuel IP Allocation, the allocation is done 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.

In DHCP terminology, there are different devices and roles. These devices and roles are:

• DHCP Server
• DHCP Client
• DHCP Relay Agent

DHCP Server is the device on which the DHCP configurations are done. All the configurations like IP Address Pools, Gateway Address etc. are done on DHCP Server. It is the mechanims that has the IP pools and provides IP addresses to the other nodes.

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: CCIE > DHCP

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