dhcp snooping enable

Function

The dhcp snooping enable command enables DHCP snooping.

The undo dhcp snooping enable command disables DHCP snooping.

By default, DHCP snooping is disabled.

Format

dhcp snooping enable

undo dhcp snooping enable

Parameters

None

Views

System view

Default Level

2: Configuration level

Task Name and Operations

Task Name	Operations
dhcp	write

Usage Guidelines

Usage Scenario

To enable DHCP snooping, run the dhcp snooping enable command. Enable DHCP snooping in the following order: globally, for a VLAN, for a BD, and for an interface. You can configure DHCP snooping functions only after DHCP snooping is enabled globally.

Prerequisites

DHCP snooping has been enabled globally by running the dhcp enable command.

Configuration Impact

The undo dhcp enable command disables DHCP snooping. However, related configurations are not deleted.

When DHCP snooping is enabled, all interfaces are in untrusted mode by default. To configure an interface as a trusted interface, perform one of the following operations:

Run the dhcp snooping trusted command on an interface to configure the interface as a trusted interface.
Run the dhcp snooping trusted command in a BD to configure all interfaces in the BD as trusted interfaces.
Run the dhcp snooping trusted interface command on a VLAN to configure an interface as a trusted interface.

Precautions

After a sub-VLAN is added to a super-VLAN, DHCP snooping cannot be enabled on the VLANIF interfaces for both the sub-VLAN and super-VLAN. Layer 3 interfaces have to be switched to Layer 2 interfaces before being added to a VLAN. Otherwise, Layer 3 interfaces cannot be added to a VLAN.
DHCP snooping cannot be enabled for both the VLAN and its VLANIF interface.
DHCP snooping cannot be enabled for both the BD and its VBDIF interface.
DHCP snooping cannot be enabled for both the Layer 2 sub-interfaces and the VBDIF interfaces.
DHCP snooping is applied to users on the AC-side interface and not applied to users on the PW-side interface.
If both DHCP snooping and DHCP relay/DHCP server are required, DHCP snooping must be enabled on the Layer 3 interface where the DHCP relay/DHCP server is deployed.
If a whitelist has been applied when DHCP snooping is enabled, ensure that whitelist rules have been configured for all valid DHCP servers in the whitelist.
When DHCP snooping is enabled in the view of a BD, VLAN, or interface where a whitelist has been applied, the following message is displayed: A whitelist has been applied. Configure complete whitelist rules for valid DHCP servers.

Example

# Enable DHCP snooping globally.

<HUAWEI> system-view
[~HUAWEI] dhcp enable
[*HUAWEI] dhcp snooping enable