arp learning multicast enable (interface view)

Function

The arp learning multicast enable command enables a specific interface to learn multicast MAC addresses and generate dynamic Address Resolution Protocol (ARP) entries.

The undo arp learning multicast enable command disables a specific interface from learning multicast MAC addresses or generating dynamic ARP entries.

By default, a device is disabled globally and a specific interface is disabled from learning multicast MAC addresses and generating dynamic ARP entries. If this function is globally enabled, the interface is enabled to learn multicast MAC addresses. If this function is globally disabled, the interface is disabled from learning multicast MAC addresses.

Format

arp learning multicast enable

undo arp learning multicast enable

Parameters

None

Views

Ethernet interface view, VLANIF interface view, or Eth-Trunk interface view

Default Level

2: Configuration level

Usage Guidelines

Usage Scenario

A MAC address corresponding to an IP address may be a multicast MAC address. In this case, a network administrator has to configure a static ARP entry. A device can generate dynamic ARP entries if enabled to learn multicast MAC addresses. This way reduces a network administrator's workload of configuring static ARP entries and reduces network operation and maintenance costs.

Configuration Impact

After a device is enabled to learn multicast MAC addresses, the device may be attacked by ARP attack packets carrying multicast MAC addresses as source MAC addresses.

Precautions

The following rules apply:

If the arp learning multicast enable command is run in both the system view and interface view, the command on the interface takes effect.
If the arp learning multicast enable command is run globally but not run in the interface view, the command takes effect globally.
If the arp learning multicast enable command is run in the interface view but not run globally, the command on the interface takes effect.

If the arp learning multicast enable command is run in both the system view and interface view, the undo arp learning multicast enable command run on the interface takes effect globally. The interface remains enabled to learn multicast MAC addresses. To disable the interface from learning multicast MAC addresses, run the arp learning multicast disable command on the interface.

This command cannot be configured on a sub-interface, and the configuration of the interface takes effect on its sub-interfaces. If an interface is enabled to learn multicast MAC addresses through ARP, its sub-interfaces also have this function enabled.

Example

# Enable a specific interface to learn multicast MAC addresses.

<sysname> system-view

[sysname] interface GigabitEthernet 0/0/1

[sysname-GigabitEthernet 0/0/1] arp learning multicast enable