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V-221084

CAT II (Medium)

The Cisco switch must be configured to have Internet Control Message Protocol (ICMP) unreachable messages disabled on all external interfaces.

Rule ID

SV-221084r999693_rule

STIG

Cisco NX OS Switch RTR Security Technical Implementation Guide

Version

V3R4

CCIs

CCI-002385

Discussion

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.

Check Content

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

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