2-7
Currently, the DHCP relay agent handshake function on an S4500 series switch can only interoperate
with a Windows 2000 DHCP server.

Enabling unauthorized DHCP server detection

If there is an unauthorized DHCP server in the network, when a client applies for an IP address, the
unauthorized DHCP server may assign an incorrect IP address to the DHCP client.
With this feature enabled, upon receiving a DHCP message with the siaddr field (IP addresses of the
servers offering IP addresses to the client) not being 0 from a client, the DHCP relay agent will record
the value of the siaddr field and the receiving interface. The administrator can use this information to
check out any DHCP unauthorized servers.
Follow these steps to enable unauthorized DHCP server detection:
To do… Use the command… Remarks
Enter system view system-view —
Enable unauthorized DHCP
server detection dhcp-server detect Required
Disabled by default.
With the unauthorized DHCP server detection enabled, the relay agent will log all DHCP servers,
including authorized ones, and each server is recorded only once until such information is removed and
is recorded again. The administrator needs to find unauthorized DHCP servers from the system log
information.
Configuring the DHCP Relay Agent to Support Option 82

Prerequisites

Before configuring Option 82 support on a DHCP relay agent, you need to:
z Configure network parameters and relay function of the DHCP relay device.
z Perform assignment strategy-related configurations, such as network parameters of the DHCP
server, address pool, and lease time.
z The routes between the DHCP relay agent and the DHCP server are reachable.

Enabling Option 82 support on a DHCP relay agent

Follow these steps to enable Option 82 support on a DHCP relay agent:
To do… Use the command… Remarks
Enter system view system-view —