Chapter 1 Arp Configuration; Introduction To Arp; Arp Function; Arp Message Format - H3C S3100 8C SI Operation Manual

Operation Manual – ARP
H3C S3100 Series Ethernet Switches

Chapter 1 ARP Configuration

1.1 Introduction to ARP

1.1.1 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 (MAC
address, for example) of the destination host or the next hop. To this end, the IP
address must be resolved into the corresponding data link layer address.
Note:
Unless otherwise stated, a data link layer address in this chapter refers to a 48-bit
Ethernet MAC address.

1.1.2 ARP Message Format

ARP messages are classified as ARP request messages and ARP reply messages.
Figure 1-1
As for an ARP request, all the fields except the hardware address of the receiver
field are set. The hardware address of the receiver is what the sender requests for.
As for an ARP reply, all the fields are set.
illustrates the format of these two types of ARP messages.
1-1
Chapter 1 ARP Configuration