ZyXEL Communications MES-2110 manual Dhcp Relay Configuration, Dhcp Relay Agent Information, 137

18

DHCP Relay Configuration

18.1 Overview

Configure DHCP relay on the MES-2110 if the DHCP clients and the DHCP server are not in the same broadcast domain. During the initial IP address leasing, the MES-2110 helps to relay network information (such as the IP address and subnet mask) between a DHCP client and a DHCP server. Once the DHCP client obtains an IP address and can connect to the network, network information renewal is done between the DHCP client and the DHCP server without the help of the MES-2110.

The MES-2110 can be configured as a global DHCP relay. This means that the MES-2110 forwards all DHCP requests from all domains to the same DHCP server. You can also configure the MES-2110 to relay DHCP information based on the VLAN membership of the DHCP clients.

18.1.1 DHCP Relay Agent Information

The MES-2110 can add information about the source of client DHCP requests that it relays to a DHCP server by adding Relay Agent information. This helps provide authentication about the source of the requests. The DHCP server can then provide an IP address based on this information. Please refer to RFC 3046 for more details.

The DHCP Relay Agent feature adds an additional parameter to the Option 82 field. The Option 82 field is in the DHCP headers of client DHCP request frames that the MES-2110 relays to a DHCP server.

The following describes the DHCP relay information that the MES-2110 sends to the DHCP server:

Table 51 Relay Agent Information

FIELD LABELS	DESCRIPTION
Slot ID	(1 byte) This value is always 0 for stand-alone non-card based
	switches.
Port ID	(1 byte) This is the port that the DHCP client is connected to.

MES-2110 User’s Guide

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