4000 Router Series Layer 3 - IP Services Configuration Guide

Table 4 Handling strategies

If a DHCP request

has…

Handling

strate

DHCP snooping…

Option 82

Drop Drops the message.

Keep Forwards the message without changing Option 82.

Replace

Forwards the message after replacing the original Option 82 with

the Option 82 padded according to the configured padding format,

padding content, and code type.

No Option 82 N/A

Forwards the message after adding the Option 82 padded

according to the configured padding format, padding content, and

code type.

DHCP snooping configuration task list

Tasks at a glance

(Required.) Configuring basic DHCP snooping

(Optional.) Configuring Option 82

(Optional.) Saving DHCP snooping entries

(Optional.) Enabling DHCP starvation attack protection

(Optional.) Enabling DHCP-REQUEST attack protection

(Optional.) Configuring DHCP packet rate limit

Configuring basic DHCP snooping

Follow these guidelines when you configure basic DHCP snooping:

• Specify the ports connected to authorized DHCP servers as trusted ports to make sure that DHCP

clients can obtain valid IP addresses. The trusted ports and the ports connected to DHCP clients must

be in the same VLAN.

• Layer 2 Ethernet interfaces can be specified as trusted ports.

• DHCP snooping can work with QinQ to record VLAN tags for DHCP packets received from clients.

For more information about QinQ, see Layer 2—LAN Switching Configuration Guide.

To configure basic DHCP snooping:

Step Command Remarks

1. Enter system view.

system-view N/A

2. Enable DHCP snooping.

dhcp snooping enable

By default, DHCP snooping is

disabled.

3. Enter interface view.

interface interface-type

interface-number

This interface must connect to the

DHCP server.