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The Cisco router must be configured to have Gratuitous ARP disabled on all external interfaces.


Overview

Finding ID Version Rule ID IA Controls Severity
V-216653 CISC-RT-000150 SV-216653r531086_rule Medium
Description
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.
STIG Date
Cisco IOS XE Router RTR Security Technical Implementation Guide 2021-09-16

Details

Check Text ( C-17886r287916_chk )
Review the configuration to determine if gratuitous ARP is disabled. The following command should not be found in the router 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 (F-17884r287917_fix)
Disable gratuitous ARP as shown in the example below:

R5(config)#no ip gratuitous-arps