3Com Switch 8800 Family Configuration Guide

706 CHAPTER 57: DHCP CONFIGURATION
5 After receiving the DHCP request packet forwarded by the DHCP relay, the DHCP
server records the information carried by the option in the packet. Then, the DHCP
server sends to the DHCP relay a response packet which carries the DHCP
configuration information and Option 82 information.
6 After receiving the response packet sent by the DHCP server, the DHCP relay strips
Option 82 information in the packet. Then, it forwards the packet that carries the
DHCP configuration information to the DHCP client.
n
The request packets sent by a DHCP client fall into two types: DHCP_DISCOVER
packets and DHCP_REQUEST packets. The DHCP relay device adds Option 82 into
both types of request packets. This is because that the DHCP servers from different
manufacturers process the request packets in different ways. Some of them
process Option 82 in the DHCP_DISCOVER packets, while others process Option
82 in the DHCP_REQUEST packets.
Configuring Option 82
Supply on DHCP Relay
Configuration Prerequisites
Before enabling Option 82 support on DHCP relay, you should configure:
■ The network parameters and the relay function on the DHCP relay
■ The network parameters, the parameters related to the allocation strategy such
as the address pools and the address allocation lease on the DHCP server.
In addition, you should make proper configuration to ensure that the DHCP relay
and the DHCP server devices are reachable to each other.
For detailed configurations, refer to DHCP section in the "Network Layer
Protocols" in this manual.
Enabling Option 82 Support on DHCP Relay
The configurations here can only be performed on the network devices where the
DHCP relay function is enabled.
Perform the following configuration in VLAN interface view to configure the
Option 82 support on DHCP relay for the current VLAN Interface.
Tabl e 654 Enable Option 82 support on DHCP relay on the current VLAN interface
Operation Command Remarks
Enter system view system-view -
Create and enter VLAN
interface view
interface vlan-interface
vlan-id
Required
The corresponding VLAN
must exist
Enable Option 82 support on
DHCP relay
dhcp relay information
enable
Required
This feature is disabled by
default