Operation Manual – ARPH3C S7500 Series Ethernet Switches Chapter 1 ARP Configuration1-1Chapter 1 ARP ConfigurationWhen configuring ARP, go to these sections for information you are interested in:z Introduction to ARPz Configuring ARPz Displaying and Maintaining ARP Configuration1.1 Introduction to ARPAddress Resolution Protocol (ARP) is used to map network layer protocol addresses(IP addresses) to corresponding data link layer hardware addresses (MAC addresses).1.1.1 Necessity of ARPNetwork devices can directly identify Layer 2 MAC addresses instead of Layer 3 IPaddresses. For a Layer 3 packet to be received by its destination host, it must carry theMAC address of the destination host. So, before sending a packet, the source devicemust map the destination IP address to the MAC address of the destination device.1.1.2 ARP Packet FormatThere are two types of ARP packets: ARP request and ARP reply. Figure 1-1 illustratesthe structure of the two types of ARP packets. In this figure:z All fields except for the target hardware address field are used in an ARP request.The target hardware address is just what the sender wants to obtain.z All fields are used in an ARP reply.Hardware type (16 bits)Protocol type (16 bits)Length of hardware address Length of prOperator (16 bits)Hardware address of the seIP address of the senderHardware address of the recIP address of the receiverotocol addressndereiverHardware type (16 bits)Hardware type (16 bits)Protocol type (16 bits)Length of hardware address Length of prOperator (16 bits)Hardware address of the seIP address of the senderHardware address of the recIP address of the receiverotocol addressndereivertFigure 1-1 ARP packet forma
