Chapter 1 Arp Configuration; Introduction To Arp; Necessity Of Arp; Arp Packet Format - H3C S7500 Series Operation Manual

Operation Manual – ARP
H3C S7500 Series Ethernet Switches

Chapter 1 ARP Configuration

When configuring ARP, go to these sections for information you are interested in:

Introduction to ARP

Configuring ARP
Displaying and Maintaining ARP Configuration
1.1 Introduction to ARP
Address Resolution Protocol (ARP) is used to map network layer protocol addresses
(IP addresses) to corresponding data link layer hardware addresses (MAC addresses).

1.1.1 Necessity of ARP

Network devices can directly identify Layer 2 MAC addresses instead of Layer 3 IP
addresses. For a Layer 3 packet to be received by its destination host, it must carry the
MAC address of the destination host. So, before sending a packet, the source device
must map the destination IP address to the MAC address of the destination device.

1.1.2 ARP Packet Format

There are two types of ARP packets: ARP request and ARP reply.
the structure of the two types of ARP packets. In this figure:
All fields except for the target hardware address field are used in an ARP request.
The target hardware address is just what the sender wants to obtain.
All fields are used in an ARP reply.
Length of hardware address Length of pr Length of hardware address Length of pr
Figure 1-1 ARP packet forma
Hardware type (16 bits) Hardware type (16 bits) Hardware type (16 bits)
Protocol type (16 bits) Protocol type (16 bits)
Operator (16 bits) Operator (16 bits)
Hardware address of the se Hardware address of the se
IP address of the sender IP address of the sender
Hardware address of the rec Hardware address of the rec
IP address of the receiver IP address of the receiver
t
1-1
Chapter 1 ARP Configuration
otocol address otocol address
nder nder
eiver eiver
Figure 1-1 illustrates