I connected 4 pcs to a switch, I used pc 1 to ping another pc(pc 3) and used wireshark on all the pc's. The one that sent the ping sent out an arp request and received 4 request and replies from the pc it pinged. The pc (pc 3) that was pinged had a total of 4 request and replies. The other two PC's (pc 2 and pc 4) connected to the switch only showed 1 request for the pc pinged and a reply from that pc. Is this due to the arp request?

1 Answer 1


Is this due to the arp request?


ARP request is broadcast, In general, When a switch receives a broadcast message(ARP or otherwise) it will send it out of all interfaces apart from the interface it was received. Now which PC received how many requests would depend upon the topology, but because the message was broadcasted, each PC is bound to receive the ARP request packet.

Now for the ARP reply.

ARP reply is unicast, it is sent from the ARP request receiver to the ARP request sender.

So it is not necessary that other devices will see the ARP reply as the message is specifically sent for a particular device.

P.S. The other devices may see the ARP reply in certain cases like the switch has not learned the MAC addresses and thus floods the reply packet.

You can get a better idea about unicast, broadcast ARP messages here, and about flooding here

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