Reference Guide

IPv4 Routing | 411
ARP Learning via Gratuitous ARP
Gratuitous ARP can mean an ARP request or reply. In the context of ARP Learning via Gratuitous ARP on
FTOS, the gratuitous ARP is a request. A Gratuitous ARP Request is an ARP request that is not needed
according to the ARP specification, but one that hosts may send to:
• detect IP address conflicts
• inform switches of their presence on a port so that packets can be forwarded
• update the ARP table of other nodes on the network in case of an address change
In the request, the host uses its own IP address in the Sender Protocol Address and Target Protocol Address
fields.
Command Syntax Command Mode Purpose
clear arp-cache [interface | ip
ip-address] [no-refresh]
EXEC privilege Clear the ARP caches for all interfaces or for a specific
interface by entering the following information:
• For a 1-Tengigabit Ethernet interface, enter the keyword
TengigabitEthernet followed by the slot/port
information.
• For a port channel interface, enter the keyword
port-channel followed by a number from 1 to 255 for
TeraScale and ExaScale.
• For a 10-Tengigabit Ethernet interface, enter the keyword
TengigabitEthernet followed by the slot/port
information.
• For a VLAN interface, enter the keyword
vlan followed
by a number between 1 and 4094.
• For a 40-Tengigabit Ethernet interface, enter the keyword
fortyGigE followed by the slot/port information.
ip ip-address (OPTIONAL) Enter the keyword ip followed
by the IP address of the ARP entry you wish to clear.
no-refresh (OPTIONAL) Enter the keyword no-refresh to
delete the ARP entry from CAM. Or use this option with
interface or ip ip-address to specify which dynamic ARP
entries you want to delete.
Note: Transit traffic may not be forwarded during the
period when deleted ARP entries are resolved again
and re-installed in CAM. Use this option with extreme
caution.
Task Command Syntax Command Mode
Enable ARP learning via gratuitous ARP. arp learn-enable CONFIGURATION