arp learning multicast disable

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.

If a device is globally enabled to learn multicast MAC addresses, all interfaces on the device will learn multicast MAC addresses carried in ARP packets. The ARP packets that the interfaces receive carry multicast MAC addresses as the source MAC addresses. This case increases the consumption of system resources and affects services run on a network. Running the arp learning multicast disable command on a specific interface disables the interface from learning multicast MAC addresses.

Configuration Impact

After a specific interface is disabled from learning MAC addresses, the interface silently discards the ARP packets that it receives. The ARP packets carry multicast MAC addresses that the interface does not learn as the source MAC addresses. Discarding the ARP packets may cause services not to run properly on the network.

In a multicast service scenario, if the fixed mapping between IP addresses and multicast MAC addresses is not specified using the arp static command, ensure a specific interface is enabled from learning multicast MAC addresses. This way ensures multicast services to run properly.

Precautions

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 disabled from learning multicast MAC addresses through ARP, its sub-interfaces also have this function disabled.