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Dynamic Host Configuration Protocol

Protocol Introduction

The Dynamic Host Configuration Protocol (DHCP) provides configuration parameters to Internet hosts in a client-server model. DHCP server hosts allocate network addresses and deliver configuration parameters to other (client) hosts.

DHCP consists of two components: a protocol for delivering host-specific configuration parameters from a server to a host and a mechanism for allocation of network addresses to hosts.

IP Address Allocation
DHCP supports three mechanisms for IP address allocation.

Configuration Parameters Delivery
The client sends a message to request configuration parameters and the server responds with a message carrying the desired parameters back to the client.

BOOTP Compatibility
The format of DHCP messages is based on the format of BOOTP messages due to the following reasons:
  1. From the client's point of view, DHCP is an extension of the BOOTP mechanism. This behavior allows existing BOOTP clients to interoperate with DHCP servers without requiring any change to the clients' initialization software.
  2. DHCP supports the BOOTP relay agent behavior.

Use of Relay Agents
DHCP does not require a server on each subnet. To allow for scale and economy, DHCP can work across routers or through the intervention of BOOTP relay agents. A realy agent listens to DHCP messages and forwards them on (and onto other network segments). This eliminates the necessity of having a DHCP server on each physical network.


  1. The two basic mechanisms in DHCP are:
  2. A relay agent is:
  3. Relay agents where created for:

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