Command Reference Guide

20 ● arp security time-out 3Com Router 5000 Family and Router 6000 Family
Command Reference
arp security time-out
Purpose Use the arp security time-out command to configure the aging time of the
authorized ARP entries.
Use the undo arp security time-out command to restore the default aging
time of the authorized ARP entries.
Syntax arp security time-out seconds
undo arp security time-out
Parameters seconds
Aging time of the authorized ARP entries (in seconds).
Valid values are 30 to 86,400.
If no value is specified, the default is 90.
Example Configure an aging time of 120 seconds for the authorized ARP entries on interface
Ethernet1/0/0.
[3Com-Ethernet1/0/0] arp security time-out 120
View This command can be used in the following views:
■ Ethernet Interface view
Description This command takes effect only when you have configured the arp security
command.
The aging of an authorized ARP entry is implemented by the mechanism of ARP ping.
The default aging time of an authorized ARP entry is the time that three ARP ping
operations takes when no responses are received. Since the ARP ping interval is 30
seconds, the default aging time of an authorized ARP entry is 90 seconds. If no
response is received for an authorized ARP entry or if the DHCP server fails to update
the entry by re-adding the entry for example, after 90 seconds elapse, the entry ages
out. The DHCP server is then notified of this.