The Cisco ACI must be configured to have Internet Control Message Protocol (ICMP) mask replies disabled on all external interfaces.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
| V-272087 | CACI-RT-000027 | SV-272087r1113993_rule | Medium |
| Description |
| The ICMP supports IP traffic by relaying information about paths, routes, and network conditions. Routers automatically send ICMP messages under a wide variety of conditions. Mask Reply ICMP messages are commonly used by attackers for network mapping and diagnosis. |
| STIG | Date |
| Cisco ACI Router Security Technical Implementation Guide | 2025-06-18 |
Details
| Check Text (C-76137r1063656_chk) |
| Review the router configuration and verify the ip mask-reply command is not enabled on any external interfaces as shown in the example below: apic1(config)# interface Ethernet0/1 apic(config-if)# no ip icmp mask-reply If the ip mask-reply command is configured on any external interface, this is a finding. |
| Fix Text (F-76044r1063657_fix) |
| Disable ip mask-reply on all external interfaces as shown below: apic1(config)# interface Ethernet0/1 apic(config-if)# no ip icmp mask-reply |