The Cisco switch must be configured to have Internet Control Message Protocol (ICMP) mask reply messages disabled on all external interfaces.
Severity | Group ID | Group Title | Version | Rule ID | Date | STIG Version |
|---|---|---|---|---|---|---|
| medium | V-221001 | SRG-NET-000362-RTR-000114 | CISC-RT-000180 | SV-221001r856406_rule | 2026-03-04 | 3 |
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.
ℹ️ Check
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
Disable ip mask-reply on all external interfaces as shown below:
SW1(config)#int g0/1
SW1(config-if)#no ip mask-reply