3Com Switch 7750 Configuration Guide

572 CHAPTER 54: ARP CONFIGURATION
ARP Table In an Ethernet network, two hosts must know each other’s MAC address for them
to communicate with each other. For this reason, each host on the network
maintains an ARP table, which contains some lately used IP address-to-MAC
address mapping entries. Note that this manual only introduces basic
implementation of ARP table. Different manufactures’ products may provide more
information about ARP table. On a Switch 7750 Ethernet switch, you can use the
display arp command to display ARP table entries.
Table 446 describes the fields of APR table.
Protocol type Type of the protocol address to be mapped. For IP
address, the value of this field is 0x0800.
Hardware address length Length of the hardware address (in bytes)
Protocol address length Length of the protocol address (in bytes)
Operation code Type of the packet, which can be:
■ 1: ARP request
■ 2: ARP reply
■ 3: RARP request
■ 4: RARP reply
Sender hardware address Hardware address of the sender
Sender IP address IP address of the sender
Target hardware address This field is null for an ARP request, and is the hardware
address of the receiver for an ARP reply.
Target IP address IP address of the receiver
Table 445 Values of the hardware type field
Value Description
1 Ethernet
2 Experimental Ethernet
3 X.25
4 Proteon ProNET (Token Ring)
5 Chaos
6 IEEE 802.x
7 ARC network
Table 444 Field descriptions of an ARP packet
Field Description
Table 446 Field descriptions of an ARP table
Field Description
IF index Index of the physical interface or port on the device owning the
physical address and IP address in the entry
Physical address Physical address of the device, a MAC address
IP address IP address of the device