Why does the destination MAC Address exist in an ARP Packet

Hi Sprout,

It’s normal.

When an ARP entry times out, the device sends an ARP request packet to the corresponding Ethernet address in the table before removing the entry. If the device does not respond within a short period of time, the device will delete the entry. The request is sent directly so as not to bother every station on the Ethernet.

This is explained in detail in [RFC 826]

https://tools.ietf.org/html/rfc826

Another alternative is to have a daemon perform the timeouts. After a suitable time, the daemon considers removing an entry. It first sends (with a small number of retransmissions if needed) an address resolution packet with opcode REQUEST directly to the Ethernet address in the table. If a REPLY is not seen in a short amount of time, the entry is deleted. The request is sent directly so as not to bother every station on the Ethernet. Just forgetting entries will likely cause useful information to be forgotten, which must be regained.