User's Manual

Table Of Contents
Configuration Guide of XGS-5240-Series
35-1
Chapter 35 Gratuitous ARP
Configuration
35.1 Introduction to Gratuitous ARP
Gratuitous ARP is a kind of ARP request that is sent by the host with its IP address as the
destination 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 hostssending ARP requests for
the gateways MAC address.
2. Gratuitous ARP is a method to prevent ARP cheating. The switchs advertising gratuitous
ARP request will force the hosts to update its ARP table cache. Thus, forged ARP of
gateway cannot function.
35.2 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.
2. Display configurations about gratuitous ARP
Command
Explanation