Users Guide
Enabling Proxy ARP
By default, Proxy ARP is enabled. To disable Proxy ARP, use the no ip proxy-arp command in the interface mode.
To re-enable Proxy ARP, use the following command.
• Re-enable Proxy ARP.
INTERFACE mode
ip proxy-arp
To view if Proxy ARP is enabled on the interface, use the show config command in INTERFACE mode. If it is not listed in the show
config command output, it is enabled. Only non-default information is displayed in the show config command output.
Clearing ARP Cache
To clear the ARP cache of dynamically learnt ARP information, use the following command.
• Clear the ARP caches for all interfaces or for a specic interface by entering the following information.
EXEC privilege
clear arp-cache [interface | ip ip-address] [no-refresh]
• ip ip-address (OPTIONAL): enter the keyword ip then the IP address of the ARP entry you wish to clear.
• no-refresh (OPTIONAL): enter the keywords no-refresh to delete the ARP entry from CAM. Or to specify which dynamic
ARP entries you want to delete, use this option with
interface or ip ip-address.
• For a port channel interface, enter the keywords port-channel then a number.
• For a 10-Gigabit Ethernet interface, enter the keyword TenGigabitEthernet then the slot/port information.
• For a 40-Gigabit Ethernet interface, enter the keyword fortyGigE then the slot/port information.
• For a port extender 1–Gigabit Ethernet interface enter the keyword peGigE then the pe-id/pe-stack—unit-id/port-number
information.
• For a VLAN interface, enter the keyword vlan then a number between 1 and 4094.
NOTE
: Transit trac 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.
ARP Learning via Gratuitous ARP
Gratuitous ARP can mean an ARP request or reply.
During ARP learning via gratuitous ARP, the gratuitous ARP is a request. A gratuitous ARP request is an ARP request that is not needed
according to the ARP specication, but one that hosts may send to:
• detect IP address conicts
• 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 elds.
When a gratuitous ARP is received, the system installs an ARP entry on all three CPUs.
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IPv4 Routing