arp learning strict (system view)

Function

The arp learning strict command enables strict ARP learning.

The undo arp learning strict command disables strict ARP learning.

By default, strict ARP learning is disabled.

Format

arp learning strict

undo arp learning strict

Parameters

None

Views

System view

Default Level

2: Configuration level

Usage Guidelines

Usage Scenario

If many user hosts send a large number of ARP packets to a device simultaneously, or attackers send bogus ARP packets to the device, the following problems occur:

Processing ARP packets consumes many CPU resources. The device learns many invalid ARP entries, which exhaust ARP entry resources and prevent the device from learning ARP entries for ARP packets from authorized users. Consequently, communication of authorized users is interrupted.
After receiving bogus ARP packets, the device incorrectly modifies the ARP entries. As a result, authorized users cannot communicate with each other.

To avoid the preceding problems, enable strict ARP learning on the gateway. This function indicates that the device learns only ARP entries for ARP Reply packets in response to ARP Request packets sent by itself. In this way, the device can defend against most ARP attacks.

Precautions

The configuration on an interface takes precedence over the global configuration.

Example

# Enable strict ARP learning.

<HUAWEI> system-view
[HUAWEI] arp learning strict