D-Link DFL-210 - NetDefend - Security Appliance, User Manual

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Chapter 5. DHCP Services
This chapter describes DHCP services in NetDefendOS.
• Overview, page 182
• DHCP Servers, page 183
• Static DHCP Assignment, page 185
• DHCP Relaying, page 187
• IP Pools, page 190
5.1. Overview
Dynamic Host Configuration Protocol (DHCP) is a protocol that allows network administrators to
automatically assign IP numbers to computers on a network.
IP Address Assignment
A DHCP Server implements the task of assigning IP addresses to DHCP clients. These addresses
come from a pre-defined IP address pool which DHCP manages. When a DHCP server receives a
request from a DHCP client, it returns the configuration parameters (such as an IP address, a MAC
address, a domain name, and a lease for the IP address) to the client in a unicast message.
DHCP Leases
Compared to static assignment, where the client owns the address, dynamic addressing by a DHCP
server leases the address to each client for a pre-defined period of time. During the lifetime of a
lease, the client has permission to keep the assigned address and is guaranteed to have no address
collision with other clients.
Lease Expiration
Before the expiration of the lease, the client needs to renew the lease from the server so it can keep
using the assigned IP address. The client may also decide at any time that it no longer wishes to use
the IP address it was assigned, and may terminate the lease and release the IP address.
The lease time can be configured in a DHCP server by the administrator.
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