The Cisco router must be configured to have Internet Control Message Protocol (ICMP) mask reply messages disabled on all external interfaces.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
| V-216747 | CISC-RT-000180 | SV-216747r856438_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 IOS XR Router RTR Security Technical Implementation Guide | 2024-08-22 |
Details
| Check Text (C-17979r288630_chk) |
| Review the router configuration and verify that ipv4 mask-reply command is not enabled on any external interfaces as shown in the example below. interface GigabitEthernet0/0/0/1 ipv4 address x.11.1.2 255.255.255.252 ipv4 mask-reply If the router configuration has the ipv4 mask-reply command is enabled on any external interfaces, this is a finding. |
| Fix Text (F-17977r288631_fix) |
| Disable ipv4 mask-reply on all external interfaces as shown below. RP/0/0/CPU0:R3(config)#int g0/0/0/1 RP/0/0/CPU0:R3(config-if)#no ipv4 mask-reply |