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-216563	CISC-RT-000150	SV-216563r856182_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 Router RTR Security Technical Implementation Guide	2024-11-25

Details

Check Text (C-17798r287073_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-17794r287074_fix)

Disable gratuitous ARP as shown in the example below:

R5(config)#no ip gratuitous-arps