Avaya Configuring BOOTP Services Bedienungsanleitung PDF herunterladen (Seite 59)

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

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• If the DHCP server can supply the requested configuration parameters, it

sends a DHCPACK packet to the client through the DHCP server.

The client examines the configuration parameters in the DHCPACK packet

and records the duration of the lease period. If the client detects a problem

with the configuration parameters, it sends a DHCPDECLINE packet to the

server and issues a new DHCPDISCOVER packet. Otherwise, the client

accepts the configuration parameters.

• If the target server cannot supply the requested configuration parameters, it

sends a DHCPNAK packet to the client through the DHCP server.

When the client receives the DHCPNAK packet, it broadcasts a new

DHCPDISCOVER packet and the process begins again.

Reacquiring the Same IP Address

A client may want to reuse an IP address that a server allocated earlier using

DHCP. In this case, the interchange between client and server omits some of the

steps described in the previous sections.

The client can acquire the same IP address again using a DHCP server by

following these steps:

The client starts the interchange by broadcasting a DHCPREQUEST packet

that contains its previous IP address in the client IP address field.

The DHCP server receives the packet, examines the client’s configuration

parameters in the options field of the DHCPREQUEST packet, and forwards

the client request information to the NetID Server Manager.

The NetID Server Manager updates its database and sends a committed

update message back to the DHCP server.

The DHCP server that originally supplied the configuration parameters

recognizes them and responds with a DHCPACK packet.

When a client receives a DHCPACK packet from the DHCP server, it accepts

or declines the parameters, as it would when receiving a new IP address.

If a client’s request is invalid (for example, if the client has moved to a new

network), servers respond with a DHCPNAK packet. If a client receives only

DHCPNAK packets, it must request a new IP address by broadcasting a

DHCPDISCOVER packet.

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Avaya Configuring BOOTP Services Bedienungsanleitung Seite 59