3.1.a [ii] ARP
resolving a known l3 address to an unknown l2 address…
i suggest you spend some time here, and with rfc 826… it is not enough to have familiarity…
Address resolution using ARP
is accomplished through the exchange of messages
between the source device seeking to perform the resolution, and the destination device that responds to it. As with other protocols, a special message format
is used containing the information required for each step of the resolution process.
ARP messages use a relatively simple format. It includes a field describing the type of message (its operational code or opcode) and information on both layer two and layer three addresses. In order to support addresses that may be of varying length, the format specifies the type of protocol used at both layer two and layer three and the length of addresses used at each of these layers
The ARP message format is designed to accommodate layer two and layer three addresses of various sizes. This diagram shows the most common implementation, which uses 32 bits for the layer three (“Protocol”) addresses, and 48 bits for the layer two hardware addresses. These numbers of course correspond to the address sizes of the Internet Protocol version 4
and IEEE 802 MAC addresses
, used by Ethernet.