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


Overview

Finding ID Version Rule ID IA Controls Severity
V-220434 CISC-RT-000180 SV-220434r622190_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. Mask Reply ICMP messages are commonly used by attackers for network mapping and diagnosis.
STIG Date
Cisco IOS Switch RTR Security Technical Implementation Guide 2021-03-19

Details

Check Text ( C-22149r508387_chk )
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 (F-22138r508388_fix)
Disable ip mask-reply on all external interfaces as shown below:

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