Arp Overview; Arp Function; Arp Message Format - 3Com MSR 50 Series Configuration Manual

30

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 549
■
"Configuring ARP" on page 552
■
"Configuring Gratuitous ARP" on page 554
■
"Configuring ARP Source Suppression" on page 555
■
"Configuring Authorized ARP" on page 555
■
"Displaying and Maintaining ARP" on page 559
■
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 155 ARP message format
Hardware Protocol
type type
1 1 2
2 2
28-byte ARP request /response
The following explains the fields in
Hardware type: This field specifies the type of a hardware address. The value
■
"1" represents an Ethernet address.
Protocol type: This field specifies the type of the protocol address to be
■
mapped. The hexadecimal value "0x0800" represents an IP address.
ONFIGURATION
Hardware address length
Protocol address length
OP Sender hardware Sender protocol
address address
6 4
Figure
Target
Target hardware
protocol
address
address
6 4
155.