arp purge slowly

Function

The arp purge slowly command enables a device to delete dynamic ARP entries after a delay when a VLANIF member interface goes Down.

The undo arp purge slowly command restores the default setting.

By default, a device deletes dynamic ARP entries immediately when a VLANIF member interface goes Down.

Format

arp purge slowly

undo arp purge slowly

Parameters

None

Views

VLANIF interface view

Default Level

2: Configuration level

Usage Guidelines

Usage Scenario

By default, when a VLANIF member interface goes Down, a device immediately deletes the dynamic ARP entries learned by the member interface. At this time, the VLANIF interface needs to relearn ARP entries to forward user traffic. However, in some special networking scenarios, such as the ring or dual-homed networking, a VLANIF member interface going Down does not necessarily mean that its interconnected interface is deleted. The outbound interfaces of ARP entries may change. In this situation, it will take a long time for the device to relearn ARP entries, interrupting user service traffic.

To minimize the preceding impact and accelerate user traffic convergence, run the arp purge slowly command to enable the device to delete dynamic ARP entries after a delay when a VLANIF member interface goes Down.

After the arp purge slowly command is configured, the device does not immediately delete dynamic ARP entries learned by a VLANIF member interface after it goes Down. Instead, it sends ARP probe packets and then deletes or updates ARP entries depending on whether it receives ARP Reply packets within the ARP aging time:

If the device does not receive ARP Reply packets, it deletes the dynamic ARP entries.
If the device receives ARP Reply packets, it updates ARP entries based on information contained in the ARP Reply packets.

Precautions

To update ARP entries, a better alternative to ARP aging mechanism is enabling the MAC address-triggered ARP entry update function, because the device learns MAC address entries faster. Therefore, to accelerate user traffic convergence, you are advised to enable ARP entry delayed deletion and the MAC address-triggered ARP entry update function using the mac-address update arp command.

The arp purge slowly and arp detect-mode unicast commands are mutually exclusive on the same VLANIF interface. If they are both run on the same VLANIF interface, the arp purge slowly command fails to take effect.

Example

# Enable a device to delete dynamic ARP entries after a delay when a member interface of VLANIF 100 goes Down.

<HUAWEI> system-view
[HUAWEI] interface vlanif 100
[HUAWEI-Vlanif100] arp purge slowly