Configuring Arp; Overview; Arp Message Format; Arp Operation - HP 1910 User Manual

Configuring ARP

This chapter describes how to configure the Address Resolution Protocol (ARP).

Overview

ARP resolves IP addresses into MAC addresses on Ethernet networks.

ARP message format

ARP messages are classified into ARP requests and ARP replies.
request/reply. Numbers in the figure refer to field lengths.
Figure 227 ARP message format
The following describe the fields in
Hardware type—The hardware address type. The value 1 represents Ethernet.
•
Protocol type—The type of the protocol address to be mapped. The hexadecimal value 0x0800
•
represents IP.
• Hardware address length and protocol address length—Length, in bytes, of a hardware address
and a protocol address, in bytes. For an Ethernet address, the value of the hardware address length
field is 6. For an IPv4 address, the value of the protocol address length field is 4.
OP—Operation code. The type of the ARP message. The value 1 represents an ARP request and 2
•
represents an ARP reply.
Sender hardware address—Hardware address of the device sending the message.
•
Sender protocol address—Protocol address of the device sending the message.
•
Target hardware address—Hardware address of the device the message is being sent to.
•
• Target protocol address—Protocol address of the device the message is being sent to.

ARP operation

As shown in
follows:
Host A looks in its ARP table to see whether there is an ARP entry for Host B. If yes, Host A uses the
1.
MAC address in the entry to encapsulate the IP packet into a data link layer frame and sends the
frame to Host B.
Figure 228, Host A and Host B are on the same subnet. Host A sends a packet to Host B as
Figure 227:
217
Figure 227 shows the format of the ARP