Gratuitous ARP（ぐらてゅいたす あーぷ）

http://www.nishimoto-site.net/archiver/ML/apache-ML/199906/msg00004.html
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192.168.2.4 -> (broadcast) ETHER Type=0806 (ARP), size = 42 bytes
192.168.2.4 -> (broadcast) ARP C Who is 192.168.2.4, 192.168.2.4 ?

ETHER: ----- Ether Header -----
ETHER:
ETHER: Packet 25 arrived at 3:15:10.00018
ETHER: Packet size = 42 bytes
ETHER: Destination = ff:ff:ff:ff:ff:ff, (broadcast)
ETHER: Source = 0:2:b3:4a:1e:44,
ETHER: Ethertype = 0806 (ARP)
ETHER:
ARP: ----- ARP/RARP Frame -----
ARP:
ARP: Hardware type = 1
ARP: Protocol type = 0800 (IP)
ARP: Length of hardware address = 6 bytes
ARP: Length of protocol address = 4 bytes
ARP: Opcode 1 (ARP Request)
ARP: Sender's hardware address = 0:2:b3:4a:1e:44
ARP: Sender's protocol address = 192.168.2.4, 192.168.2.4
ARP: Target hardware address = ?
ARP: Target protocol address = 192.168.2.4, 192.168.2.4
ARP: