Chapter 22 Dhcp Relay; Dhcp Relay Overview; Dhcp "Relay Agent Information Option; Dhcp Relay Agent Circuit Id Sub-Option Format - ZyXEL Communications GS-3012F User Manual

This chapter describes the DHCP relay and shows you how to configure the DHCP Relay
screen.

22.1 DHCP Relay Overview

DHCP (Dynamic Host Configuration Protocol, RFC 2131 and RFC 2132) allows individual
clients to obtain TCP/IP configuration at start-up from a DHCP server. You can configure the
switch to relay client DHCP requests to a DHCP server and the server's responses back to the
clients.

22.1.1 DHCP "Relay Agent Information Option"

The switch can add information to client DHCP requests that it relays to a DHCP server. This
helps provide authentication about the source of the requests. You can also specify additional
information for the switch to add to the client DHCP requests that it relays to the DHCP server.
Please refer to RFC 3046 for more details.

22.1.2 DHCP Relay Agent Circuit ID Sub-option Format

The DHCP relay agent information feature adds an Agent Information field to the option 82
field of the DHCP headers of client DHCP request frames that the switch relays to a DHCP
server. The Agent Information field that the switch adds contains an "Agent Circuit-ID sub-
option" that includes the following information about where the DHCP request was received.
• Slot ID (1 byte, this is 0 with this model)
• Port ID (1 byte)
• VLAN ID (2 bytes)
• System name (up to 32 bytes, this is optional)

22.2 DHCP Relay Configuration

To configure DHCP relay information and specify the DHCP server(s), click Advanced
Application and DHCP Relay to display the screen as shown next.

Chapter 22 DHCP Relay

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