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Configure NTP authentication
NTP authentication and the corresponding trusted key provide a reliable means of exchanging NTP
packets with trusted time sources. NTP authentication begins when the first NTP packet is created
following the configuration of keys. NTP authentication in FTOS uses the MD5 algorithm and the key is
embedded in the synchronization packet that is sent to an NTP time source.
To configure NTP authentication, use these commands in the following sequence in the
CONFIGURATION mode:
To view the NTP configuration, use the
show running-config ntp command (Figure 40) in the EXEC
privilege mode. Figure 53-5 shows an encrypted authentication key. All keys are encrypted.
Figure 53-5. show running-config ntp Command Example
FTOS Behavior: FTOS versions 8.2.1.0 and later use an encryption algorithm to store the
authentication key that is different from previous FTOS versions; beginning in version 8.2.1.0, FTOS
uses DES encryption to store the key in the startup-config when you enter the command ntp
authentication-key
. Therefore, if your system boots with a startup-configuration from an FTOS versions
prior to 8.2.1.0 in which you have configured ntp authentication-key, the system cannot correctly
decrypt the key, and cannot authenticate NTP packets. In this case you must re-enter this command
and save the running-config to the startup-config.
Step Command Syntax Command Mode Purpose
1
ntp authenticate
CONFIGURATION Enable NTP authentication.
2
ntp authentication-key number md5 key CONFIGURATION Set an authentication key. Configure the
following parameters:
number: Range 1 to 4294967295. This
number must be the same as the number in
the ntp trusted-key command.
key: Enter a text string. This text string is
encrypted.
3
ntp trusted-key number CONFIGURATION Define a trusted key. Configure a number
from 1 to 4294967295.
The number must be the same as the
number used in the ntp
authentication-key
command.
FTOS#show running ntp
!
ntp authenticate
ntp authentication-key 345 md5 5A60910F3D211F02
ntp server 11.1.1.1 version 3
ntp trusted-key 345
FTOS#
encrypted key