Operation Manual – ARPH3C S3100 Series Ethernet Switches Chapter 1 ARP Configuration1-1Chapter 1 ARP Configuration1.1 Introduction to ARP1.1.1 ARP FunctionAddress Resolution Protocol (ARP) is used to resolve an IP address into a data linklayer address.An IP address is the address of a host at the network layer. To send a network layerpacket to a destination host, the device must know the data link layer address (MACaddress, for example) of the destination host or the next hop. To this end, the IPaddress must be resolved into the corresponding data link layer address.Note:Unless otherwise stated, a data link layer address in this chapter refers to a 48-bitEthernet MAC address.1.1.2 ARP Message FormatARP messages are classified as ARP request messages and ARP reply messages.Figure 1-1 illustrates the format of these two types of ARP messages.z As for an ARP request, all the fields except the hardware address of the receiverfield are set. The hardware address of the receiver is what the sender requests for.z As for an ARP reply, all the fields are set.
