The Cisco switch must be configured to have Internet Control Message Protocol (ICMP) unreachable messages disabled on all external interfaces.
Severity | Group ID | Group Title | Version | Rule ID | Date | STIG Version |
|---|---|---|---|---|---|---|
| medium | V-221084 | SRG-NET-000362-RTR-000113 | CISC-RT-000170 | SV-221084r999693_rule | 2026-03-04 | 3 |
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.
ℹ️ Check
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
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