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-221084r622190_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	2021-03-29

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