Operation Manual – ARP
Quidway S3100 Series Ethernet Switches
Chapter 1 ARP Configuration
Huawei Technologies Proprietary
1-1
Chapter 1 ARP Configuration
1.1 Introduction to ARP
Address resolution protocol (ARP) is used to resolve IP addresses into MAC
addresses.
1.1.1 Necessity of the Address Resolution
IP address is used on the network layer and cannot be used directly for communication,
because network devices can only identify MAC addresses. To enable packets travel
on the network layer to reach the destination host, the MAC address of the host is
required. Therefore, before sending a packet, the sender needs to resolve the IP
address of the destination into the corresponding MAC address.
1.1.2 ARP Packet Structure
ARP packets are classified into 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 pro
Protocol type (16 bits)
Hardware type (16 bits)
tocol address
Figure 1-1
Structure of an ARP request/reply packet
Table 1-1 describes the fields of an ARP packet.
