The Cisco router must be configured to authenticate Network Time Protocol (NTP) sources using authentication with FIPS-compliant algorithms.

Severity
Group ID
Group Title
Version
Rule ID
Date
STIG Version
mediumV-216540SRG-APP-000395-NDM-000347CISC-ND-001150SV-216540r1156820_rule2026-02-263

Description

If NTP is not authenticated, an attacker can introduce a rogue NTP server. This rogue server can then be used to send incorrect time information to network devices, which will make log timestamps inaccurate and affect scheduled actions. NTP authentication is used to prevent this tampering by authenticating the time source.

ℹ️ Check

Review the Cisco router configuration to verify that it authenticates NTP sources using authentication with FIPS-compliant algorithms as shown in the configuration example below: ntp authentication-key 1 hmac-sha2 encrypted xxxxxx trusted-key 1 authenticate server 198.51.100.1 key 1 If the Cisco router is not configured to authenticate NTP sources using authentication with FIPS-compliant algorithms, this is a finding.

✔️ Fix

Configure the Cisco router to authenticate NTP sources using authentication with FIPS-compliant algorithms as shown in the example below: RP/0/0/CPU0:router# configure RP/0/0/CPU0:router(config)# ntp RP/0/0/CPU0:router(config-ntp)# authentication-key 1 hmac-sha2 encrypted xxxxxx RP/0/0/CPU0:router(config-ntp)# trusted-key 1 RP/0/0/CPU0:router(config-ntp)# authenticate RP/0/0/CPU0:router(config-ntp)# server 198.51.100.1 key 1 RP/0/0/CPU0:router(config-ntp)# commit