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V-220431

CAT II (Medium)

The Cisco switch must be configured to have gratuitous ARP disabled on all external interfaces.

Rule ID

SV-220431r856233_rule

STIG

Cisco IOS Switch RTR Security Technical Implementation Guide

Version

V3R3

CCIs

CCI-002385

Discussion

A gratuitous ARP is an ARP broadcast in which the source and destination MAC addresses are the same. It is used to inform the network about a host IP address. A spoofed gratuitous ARP message can cause network mapping information to be stored incorrectly, causing network malfunction.

Check Content

Review the configuration to determine if gratuitous ARP is disabled. The following command should not be found in the switch configuration: 

ip gratuitous-arps 

Note: With Cisco IOS, gratuitous ARP is enabled and disabled globally. 

If gratuitous ARP is enabled on any external interface, this is a finding.

Fix Text

Disable gratuitous ARP as shown in the example below: 

SW1(config)#no ip gratuitous-arps