Avaya Configuring SNMP, BOOTP, DHCP, and RARP Services Manual de usuario descargar pdf (Pagina 45)

SNMP, BootP, BootP/DHCP Relay, DHCP Server, and RARP Concepts

117362-C Rev 00

2-15

DHCP can allocate three types of IP addresses to DHCP clients: static DHCP

addresses, dynamic DHCP addresses, and static BootP addressess. Table 2-3

describes these types of IP addresses.

Dynamic IP Address Allocation

There are only a limited number of IP addresses in a TCP/IP network. DHCP

enables you to efficiently use and reuse IP addresses by implementing a concept

called IP address leasing. A DHCP client can lease an IP address from a DHCP

server for a fixed, configurable period of time. The lease period can range from 1

minute to 99 years. If you have more clients than IP addresses, using shorter

leases can prevent you from running out of addresses. If you have more addresses

than clients, you can use permanent addresses or you can assign fixed addresses to

specific clients.

When a lease expires, the DHCP client can contact the DHCP server to renew the

lease. Typically, the client attempts to renew the lease halfway through the lease

period. For example, if the client is granted an address with a lease time of one

hour, it asks to renew the address approximately half an hour after the client has

started to use it.

Table 2-3. IP Address Types Allocated by DHCP

IP Address Type Description

Static DHCP address An address that the DHCP server fixes to a client by a

unique key, which is typically the MAC address.

Dynamic DHCP address An address that the DHCP server allocates to a client for

fixed periods of time, called

lease times

. The client can

extend the lease so that it continues to use the same

dynamic address. When the client leaves the network, the

client typically releases the address, and the DHCP server

can assign it to another client.

Static BootP address An address that a DHCP server allocates dynamically with

no fixed time period. Unlike a dynamic DHCP address, a

static BootP address has an infinite lease time. When the

client leaves the network, it must send a message to the

DHCP server to release the address. The address is then

available for the DHCP server to reassign.

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Avaya Configuring SNMP, BOOTP, DHCP, and RARP Services Manual de usuario Pagina 45