Configuring the Transmission of GARP Packets

You can enable the generation of Gratuitous Address Resolution Protocol (GARP) packets using the ip gratuitous-arps command in Interface Configuration mode and specify the number of GARP packets to be sent at a frequency of 10 seconds. By default, three GARPs are sent at an interval of 10 seconds of one another.

Note: You must first configure the Ethernet interface for VLAN encapsulation using the encapsulation vlan command in Interface Configuration mode before configuring the transmission of GARP packets. Otherwise, an error message is displayed stating that VLAN encpasulation must be enabled on the Ethernet interface to enable configuration of GARP transmission parameters.

To configure the transmission of GARP packets:

1. Specify a Fast Ethernet, Gigabit Ethernet, or 10-Gigabit Ethernet interface.
   host1(config)#interface gigabitEthernet 2/0/1
2. Specify VLAN as the encapsulation method.
   host1(config-if)#encapsulation vlan

   The VLAN major interface is added. If an IP address is configured directly on the physical Ethernet interface and a VLAN major interface is not configured on the Ethernet interface for VLAN encapsulation, transmission of GARP packets does not take place.

3. Configure the transmission of GARP packets.
   host1(config-if)#ip gratuitous-arps 2

   In this example, two GARP packets are sent at an interval of 10 seconds when the interface state transitions from the down state to the up state, if the primary IP address is modified, or a new secondary IP address is configured.