Arp Overview - 3Com Switch 4800G 24-Port Configuration Manual

54

ARP Overview

ARP Function
ARP Message Format
ARP C
When configuring ARP, go to these sections for information you are interested in:
"ARP Overview" on page 781
■
"Configuring ARP" on page 783
■
"Configuring Gratuitous ARP" on page 785
■
"Displaying and Maintaining ARP" on page 786
■
Address Resolution Protocol (ARP) is used to resolve an IP address into a data link
layer address.
An IP address is the address of a host at the network layer. To send a network layer
packet to a destination host, the device must know the data link layer address
(such as the MAC address) of the destination host. To this end, the IP address must
be resolved into the corresponding data link layer address.
n
Unless otherwise stated, the data link layer addresses that appear in this chapter
refer to the 48-bit Ethernet MAC addresses.
Figure 235 ARP message format
Hardware Protocol
type type
2 2
The following explains the fields in Figure 235.
Hardware type: This field specifies the hardware address type. The value "1"
■
represents Ethernet.
Protocol type: This field specifies the type of the protocol address to be
■
mapped. The hexadecimal value "0x0800" represents IP.
ONFIGURATION
Hardware address length
Protocol address length
OP Sender hardware
address
1 1 2
6
28-byte ARP request/response
Sender protocol Target hardware
address address
4 6
Target
protocol
address
4