Arp Table; Arp Process - H3C S5100-SI Operation Manual

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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. S5100-SI/EI series Ethernet switches provide the
display arp command to display the information about ARP mapping entries.
ARP entries in an S5100-SI/EI series Ethernet switch can either be static entries or dynamic entries, as
described in Table
Table 1-3 ARP entries
ARP entry
Static ARP entry
Dynamic ARP entry

ARP Process

Figure 1-2 ARP process
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:
1) 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.
2) 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
mode, all hosts on this subnet can receive the request, but only the requested host (namely, Host B)
will process the request.
Value
1-3.
Generation Method
Manually configured
Dynamically generated
IEEE802.X
ARC network
Manual maintenance
ARP entries of this type age
with time. The aging period is
set by the ARP aging timer.
1-3
Description
Maintenance Mode