3Com Switch 7750 Configuration Guide Guide

Introduction to ARP 547
Figure 142 An ARP mapping table
Table 417 describes the APR mapping table fields.
ARP Implementation
Procedure
The ARP mapping table of a host is empty when the host is just started up. And
when a dynamic ARP mapping entry is not in use for a specified period of time, it
is removed from the ARP mapping table so as to save the memory space and
shorten the interval for the switch to look up entries in the ARP mapping table. For
details, refer to
Figure 143.
■ Suppose there are two hosts on the same network segment: Host A and Host
B. The IP address of Host A is IP_A and that of Host B is IP_B. To send a packet
to Host B, Host A checks its own ARP mapping table first to see if the ARP entry
Table 417 Description on the fields of an ARP table
Field Description
IF index
Index of the physical interface/port on the device owning the
physical address and IP address contained in the entry
Physical address Physical address of the device, that is, the MAC address
IP address IP address of the device
Type
Entry type, which can be:
■ 1: An entry falling out of the following three cases
■ 2: Invalid entry
■ 3: Dynamic entry
■ 4: Static entry
Entry n
…
Entry 5
Entry 4
Entry 3
Entry 2
Entry 1
TypeIP addressPhysical addressIF index