Avaya Configuring BOOTP Services Manual de usuario descargar pdf (Pagina 47)

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

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

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

describes these types of IP addresses.

Dynamic IP Address Allocation

If you have 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 1 hour,

it asks to renew the address approximately 30 minutes 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, 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 BOOTP Services Manual de usuario Pagina 47