← Back to Cisco IOS Switch RTR Security Technical Implementation Guide

V-220434

CAT II (Medium)

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

Rule ID

SV-220434r856236_rule

STIG

Cisco IOS Switch RTR Security Technical Implementation Guide

Version

V3R3

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. Mask Reply ICMP messages are commonly used by attackers for network mapping and diagnosis.

Check Content

Review the switch configuration and verify that ip mask-reply command is not enabled on any external interfaces as shown in the example below: 

interface GigabitEthernet0/1 
 ip address x.x.x.x 255.255.255.0 
 ip mask-reply 

If the ip mask-reply command is configured on any external interface, this is a finding.

Fix Text

Disable ip mask-reply on all external interfaces as shown below: 

SW1(config)#int g0/1 
SW1(config-if)#no ip mask-reply