SNR S2940-8G-v2 Switch Configuration Guide
Gratuitous ARP Configuration
Chapter 33
Gratuitous ARP Configuration
33.1 Introduction to Gratuitous ARP
Gratuitous ARP is a kind of ARP request that is sent by the host with its IP address as the desti-
nation of the ARP request.
The basic working mode for the switch is as below: The Layer 3 interfaces of the switch can be
configured to advertise gratuitous ARP packets period or the switch can be configured to enable
to send gratuitous ARP packets in all the interfaces globally.
The purpose of gratuitous ARP is as below:
1. To reduce the frequency that the host sends ARP request to the switch. The hosts in the
network will periodically send ARP requests to the gateway to update the MAC address of
the gateway. If the switch advertises gratuitous ARP requests, the host will not have to
send these requests. This will reduce the frequency the host's sending ARP requests for the
gateway's MAC address.
2. Gratuitous ARP is a method to prevent ARP cheating. The switch's advertising gratuitous
ARP request will force the hosts to update its ARP table cache. Thus, forged ARP of gateway
cannot function.
33.2 Gratuitous ARP Configuration Task List
1. Enable gratuitous ARP and configure the interval to send gratuitous ARP request
2. Display configurations about gratuitous ARP
1. Enable gratuitous ARP and configure the interval to send gratuitous ARP request.
Command Explanation
Global Configuration Mode and Interface Configuration Mode
ip gratuitous-arp <5-1200>
no ip gratuitous-arp
To enable gratuitous ARP and configure the interval to send
gratuitous ARP request.
The no command cancels the gratuitous ARP.
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