54
ARP CONFIGURATION
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
ARP Overview
ARP Function 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.
ARP Message Format
Figure 235 ARP message format
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.
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
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