3Com Switch 8800 Advanced Software V5 Configuration Guide

20
ARP CONFIGURATION
When configuring ARP, go to these sections for information you are interested in:
■ “ARP Overview” on page 193
■ “Configuring ARP” on page 195
■ “Configuring Gratuitous ARP” on page 197
■ “Configuring ARP Source Suppression” on page 198
■ “Configuring ARP Defense against IP Packet Attack” on page 199
■ “Displaying and Maintaining ARP” on page 199
ARP Overview
ARP Function Address resolution protocol (ARP) is used to resolve an IP address into a MAC
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 MAC address of the
destination host. To this end, the IP address must be resolved into the
corresponding MAC address. Each host maintains an IP-to-MAC mapping table
that contains IP and MAC addresses of devices that communicated with the host
recently.
ARP Message Format Figure 57 ARP message format
The following explains the fields in Figure 57.
■ Hardware type: This field specifies the type of a hardware address. The value
"1" represents an Ethernet address.
2211
2
4664
Hardware address length
Protocol address length
28-byte ARP request/response
Protocol
type
Hardware
type
OP
Sender hardware
address
Sender protocol
address
Target hardware
address
Target
protocol
address