Configuring Unicast ARP Probe

To improve network security, some devices do not support broadcast packets.

• Before an ARP entry ages out, the local device broadcasts an ARP request packet in an attempt to update the ARP entry based on the reply from a peer device. If the peer device does not support broadcast packets, it does not respond to the broadcast ARP request packet, so the local device considers the peer device offline and deletes the ARP entry. As a result, services will be interrupted between the two devices.
• If the local device is new, it will broadcast an ARP request packet to learn the MAC addresses of other devices. If a peer device does not support broadcast packets, it will discard the ARP request packet, so the local device will not learn the peer device's MAC address. As a result, new services will not be started between the two devices.

To resolve these problems, enable the unicast ARP probe function. This function enables a local interface to send a unicast ARP request packet that carries the specified IP and MAC addresses. The unicast ARP probe function improves network security, without compromising service stability.

Before configuring unicast ARP probe, complete the following tasks:

• Connect interfaces and set physical parameters for the interfaces to ensure that the physical interface status is Up.

• Configure link layer protocol parameters on interfaces to ensure that the link layer protocol is Up.

To configure unicast ARP probe, you need the following data.