H3C Technologies H3C S3100 Series Switches - Manual (Page 368)

Operation Manual – ARP
H3C S3100-52P Ethernet Switch Chapter 1 ARP Configuration
1-1
Chapter 1 ARP Configuration
1.1 Introduction to ARP
Address resolution protocol (ARP) is used to map IP addresses to the corresponding
MAC addresses so that packets can be delivered to their destinations correctly.
1.1.1 Necessity of the Address Resolution
After a packet is forwarded to the destination network, MAC address is necessary for
the packet to reach the very device. So the destination IP address carried in a packet
need to be translated into the corresponding MAC address.
1.1.2 ARP Packet Structure
ARP packets are classified as ARP request packets and ARP reply packets. Figure 1-1
illustrates the structure of these two types of ARP packets.
z
As for an ARP request packet, all the fields except the hardware address of the
receiver field are set. The hardware address of the receiver is what the sender
request for.
z
As for an ARP reply packets, all the fields are set.
IP address of the receiver
Hardware address of the receiver
IP address of the sender
Hardware address of the sender
Operator (16 bits)
Length of the hardware address Length of pr
Protocol type (16 bits)
Hardware type (16 bits)
otocol address
Figure 1-1
Structure of an ARP request/reply packet
Table 1-1 describes the fields of an ARP packet.