The Cisco switch must be configured to have Internet Control Message Protocol (ICMP) unreachable messages disabled on all external interfaces.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
| V-221084 | CISC-RT-000170 | SV-221084r999693_rule | Medium |
| Description |
| The ICMP supports IP traffic by relaying information about paths, routes, and network conditions. Switches automatically send ICMP messages under a wide variety of conditions. Host unreachable ICMP messages are commonly used by attackers for network mapping and diagnosis. |
| STIG | Date |
| Cisco NX OS Switch RTR Security Technical Implementation Guide | 2024-12-20 |
Details
| Check Text (C-22799r409741_chk) |
| Review the switch configuration to determine if it is compliant with this requirement. The ip unreachables command must not be found on any interface as shown in the example below: interface Ethernet2/7 no switchport ip address x.22.4.2/30 ip unreachables If ICMP unreachable notifications are sent from any external interfaces, this is a finding. |
| Fix Text (F-22788r409742_fix) |
| Disable ip unreachables on all external interfaces as shown below: SW1(config)# int e2/7 SW1(config-if)# no ip unreachables SW1(config-if)# end |