3Com Switch 7750 Configuration Guide Guide

546 CHAPTER 52: ARP CONFIGURATION
ARP Table In an Ethernet, the MAC addresses of two hosts must be available for the two
hosts to communicate with each other. Each host in an Ethernet maintains an ARP
mapping table, where the latest used IP address-to-MAC address mapping entries
are stored. Note that this manual only introduces the basic implementation of the
mapping table. Different products of different manufactures may provide more
information about the mapping table. The Switch 7750 Family provides the
display arp command to display the information about ARP mapping entries for
which you can refer to ARP Command Manual.
Figure 142 shows the structure of
an ARP mapping table.
Tabl e 415 Description on the fields of an ARP packet
Field Description
Hardware Type
Identifies the type of the hardware interface.
Refer to
Table 416 for the information about
the field values.
Protocol type
Protocol type specifies the type of protocol
address being mapped. Its value is 0x0800 for
IP addresses.
Length of the hardware address Hardware address length (in bytes)
Length of protocol address Protocol address length (in bytes)
Operator
Indicates the type of a data packets, which
can be:
■ 1: ARP request packets
■ 2: ARP reply packets
■ 3: RARP request packets
■ 4: RARP reply packets
Hardware address of the sender Hardware address of the sender
IP address of the sender IP address of the sender
Hardware address of the receiver
■ For an ARP request packet, this field is null.
■ For an ARP reply packet, this field carries
the hardware address of the receiver.
IP address of the receiver IP address of the receiver
Tabl e 416 Description on the values of the hardware type field
Value Description
1 Ethernet
2 Experimental Ethernet
3 X.25
4 Proteon ProNET
5 Chaos
6 IEEE802.X
7 ARC network