arp learning passive enable

Function

The arp learning passive enable command enables passive ARP that allows a backup device in a VRRP group to learn ARP entries after receiving an ARP request message sent to a virtual IP address.

The undo arp learning passive enable command disables passive ARP.

By default, passive ARP is disabled so that a backup device in a VRRP group does not learn ARP entries after receiving an ARP request message sent to a virtual IP address.

Format

arp learning passive enable

undo arp learning passive enable

Parameters

None

Views

System view

Default Level

2: Configuration level

Task Name and Operations

Task Name	Operations
arp	write

Usage Guidelines

Usage Scenario

After the master and backup devices in a VRRP group receive an ARP request message sent to a virtual IP address, only the master device learns ARP entries and responds to the sender with the virtual MAC address. If a link or device fault causes the VRRP group to perform a master/backup switchover, a backup device must learn ARP entries on the user side before taking over traffic. As a result, service traffic is interrupted for a short time.

After you run the arp learning passive enable command to enable passive ARP, a backup device in a VRRP group learns ARP entries after receiving an ARP request message sent to a virtual IP address. If a VRRP group performs a master/backup switchover, the new master device can take over traffic without needing to relearn ARP entries, ensuring service continuity.

Precautions

When both passive ARP and strict ARP learning are enabled, strict ARP learning takes effect in priority.
When both passive ARP and ARP dual-device hot backup are enabled, ARP dual-device hot backup takes effect in priority. Specifically, the interface enabled with dual-device hot backup on the VRRP backup device does not learn ARP entries with the destination IP address as a virtual IP address. Instead, ARP learning relies on backup of the VRRP master device.

Example

# Enable passive ARP.

<HUAWEI> system-view
[~HUAWEI] arp learning passive enable