Gratuitous ARP on S series switches

An S series switch (except the S1700 switch�? sends an ARP Request packet with the destination address being its own IP address. This operation is called gratuitous ARP. Gratuitous ARP provides the following functions:
1. Checks the repetitious IP addresses. Normally, the device should not receive an ARP Reply after it sends an ARP Request with the destination address being its own IP address. If the device receives a reply, another device on the network is configured with the same IP address.
2. Declares a new MAC address. If the device has replaced its NIC and the MAC address changes, the device sends a gratuitous ARP packet to declare the change to all hosts before the aging of ARP entries.

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