Method used to configure the gratuitous ARP on USG firewalls

The gratuitous ARP packet is a special ARP packet. Both the sender IP address and destination IP address carried in the gratuitous ARP packet are the local IP address. The sender MAC address is the local MAC address, and the destination MAC address is the broadcast address.
The gratuitous ARP has the following functions: 1. It is used to check duplicated IP addresses. In normal situations, no ARP response is received. If an ARP response is received, a duplicated IP address exists on the existing network. 2. It is used to advertise a new MAC address. If the NIC of the sender is changed, the MAC address is changed accordingly. To advertise the new MAC address to all hosts before the ARP entry is aged, the sender can send a gratuitous ARP.
By configuring the gratuitous ARP, devices can positively learn and send gratuitous ARP packets.
To configure the gratuitous ARP packet learning, run the gratuitous-arp learn enable command in the interface view. By default, the gratuitous ARP packet learning is enabled for the interface.
To configure the gratuitous ARP packet sending, run the gratuitous-arp send enable [ interval interval ] command in the interface view. By default, the gratuitous ARP packet sending is disabled for the interface.

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