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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.


Finding ID Version Rule ID IA Controls Severity
V-221001 CISC-RT-000180 SV-221001r856406_rule Medium
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.
Cisco IOS XE Switch RTR Security Technical Implementation Guide 2023-09-13


Check Text ( C-22716r408797_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
ip mask-reply

If the ip mask-reply command is configured on any external interface, this is a finding.
Fix Text (F-22705r408798_fix)
Disable ip mask-reply on all external interfaces as shown below:

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