ARP and RARP

    Address Resolution Protocol (ARP) is used to identify the hardware address (MAC) of a particular IP. For Computers on Network simply an IP Address is not enough to communicate, they need MAC address which is a layer 2 address whereas IP is a layer 3 address.

FF-FF-FF-FF-FF-FF -  Broadcast, this data will spread all over the Local Area Network , which host has the IP 192.168.1.2      will pick the data and reply back it’s MAC to the Source address.

My IP – Source IP

Your IP - Destination

As per the above picture User A wants to communicate with User B, before the communication takes place ARP generates a request to the local network to know the MAC address of User B which is a Broadcast. Reply from the User B is Unicast. Once User A receives the MAC address it stores in ARP Cache Memory.

To see ARP Cache:

                                    Start => Run => type cmd

C:\> ARP -a