H3C Technologies H3C WX3000 Series Unified Switches - Manual (Page 398)

39-3
Value Description
5 Chaos
6 IEEE802.X
7 ARC network
ARP Table
In an Ethernet, the MAC addresses of two hosts must be available for the two hosts to communicate
with each other. Each host in an Ethernet maintains an ARP table, where the latest used IP
address-to-MAC address mapping entries are stored. The device provides the display arp command to
display the information about ARP mapping entries.
ARP entries in a device can either be static entries or dynamic entries, as described in Table 40-3 .
Table 40-3 ARP entries
ARP entry Generation Method Maintenance Mode
Static ARP entry Manually configured Manual maintenance
Dynamic ARP entry Dynamically generated
ARP entries of this type age with time. The aging
period is set by the ARP aging timer.
ARP Process
Figure 40-2 ARP process
Sender MAC
address
00a0-2470 -febd
Target IP
address
192.168.1.1
Target IP
address
192.168 .1. 2
Host A
192.168.1.1
0002-6779-0f4c
Host B
192. 168.1.2
00a0-2470 -febd
Target MAC
address
0000 -0000-0000
Sender IP
address
192 .168.1.1
Sender IP
address
192.168.1. 2
Sender MAC
address
Target MAC
address
0002-6779-0f4c
0002 -6779 -0f4c
Suppose that Host A and Host B are on the same subnet and that Host A sends a message to Host B.
The resolution process is as follows:
2) Host A looks in its ARP mapping table to see whether there is an ARP entry for Host B. If Host A
finds it, Host A uses the MAC address in the entry to encapsulate the IP packet into a data link layer
frame and sends the frame to Host B.
3) If Host A finds no entry for Host B, Host A buffers the packet and broadcasts an ARP request, in
which the source IP address and source MAC address are respectively the IP address and MAC
address of Host A and the destination IP address and MAC address are respectively the IP
address of Host B and an all-zero MAC address. Because the ARP request is sent in broadcast