3Com Switch 7750 Configuration Guide

Troubleshooting DHCP Relay Agent 621

# Enable DHCP.

[SW7750] dhcp enable

# Create DHCP server group 1 and configure an IP address of 202.38.1.2 for it.

[SW7750] dhcp-server 1 ip 202.38.1.2

# Map VLAN-interface 2 to DHCP server group 1.

[SW7750] interface Vlan-interface 2

[SW7750-Vlan-interface2] dhcp-server 1

# Configure an IP address for VLAN-interface 2, so that this interface is on the

same network segment with the DHCP clients.

[SW7750-Vlan-interface2] ip address 10.110.1.1 255.255.0.0

You need to perform corresponding configurations on the DHCP server to enable

the DHCP clients to obtain IP addresses from the DHCP server. The DHCP server

configurations vary with different DHCP server devices, so the configurations are

omitted.

Troubleshooting DHCP

Relay Agent

Symptom

A client fails to obtain configuration information through a DHCP relay agent.

Analysis

This problem may be caused by improper DHCP relay agent configuration. When a

DHCP relay agent operates improperly, you can locate the problem by enabling

debugging and checking the information about debugging and interface state

(You can display the information by executing the corresponding display

command).

Solution

■ Check if DHCP is enabled on the DHCP server and the DHCP relay agent.

■ Check if an address pool that is on the same network segment with the DHCP

clients is configured on the DHCP server.

■ Check if a reachable route is configured between the DHCP relay agent and the

DHCP server.

■ Check the DHCP relay agent-enabled network devices. Check if the correct

DHCP server group is configured on the interface connecting the network

segment where the DHCP client resides. Check if the IP address of the DHCP

server group is correct.