System Time and Date | 1075Configure NTP authenticationNTP authentication and the corresponding trusted key provide a reliable means of exchanging NTPpackets with trusted time sources. NTP authentication begins when the first NTP packet is createdfollowing the configuration of keys. NTP authentication in FTOS uses the MD5 algorithm and the key isembedded in the synchronization packet that is sent to an NTP time source.To configure NTP authentication, use these commands in the following sequence in theCONFIGURATION mode:To view the NTP configuration, use the show running-config ntp command (Figure 40) in the EXECprivilege mode. Figure 53-5 shows an encrypted authentication key. All keys are encrypted.Figure 53-5. show running-config ntp Command ExampleFTOS Behavior: FTOS versions 8.2.1.0 and later use an encryption algorithm to store theauthentication key that is different from previous FTOS versions; beginning in version 8.2.1.0, FTOSuses DES encryption to store the key in the startup-config when you enter the command ntpauthentication-key. Therefore, if your system boots with a startup-configuration from an FTOS versionsprior to 8.2.1.0 in which you have configured ntp authentication-key, the system cannot correctlydecrypt the key, and cannot authenticate NTP packets. In this case you must re-enter this commandand save the running-config to the startup-config.Step Command Syntax Command Mode Purpose1 ntp authenticate CONFIGURATION Enable NTP authentication.2 ntp authentication-key number md5 key CONFIGURATION Set an authentication key. Configure thefollowing parameters:number: Range 1 to 4294967295. Thisnumber must be the same as the number inthe ntp trusted-key command.key: Enter a text string. This text string isencrypted.3 ntp trusted-key number CONFIGURATION Define a trusted key. Configure a numberfrom 1 to 4294967295.The number must be the same as thenumber used in the ntpauthentication-key command.FTOS#show running ntp!ntp authenticatentp authentication-key 345 md5 5A60910F3D211F02ntp server 11.1.1.1 version 3ntp trusted-key 345FTOS#encrypted key
