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-216653r855814_rule | CCI-002385 | 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 | 2025-05-16 | |||
Details
Check Text (C-216653r855814_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