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Catalyst 2960 Switch SoftwareConfiguration Guide
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Chapter6 Administering the Swi tch
Managing the System Time and Date
Configuring NTP Authentication
This procedure must be coordinated with the administrator of the NTP server; the information you
configure in this procedure must be matched by the servers used by the switch to synchronize its time to
the NTP server.
Beginning in privileged EXEC mode, follow these steps to authenticate the associations (communications
between devices running NTP that provide for accurate timekeeping) with other devices for security
purposes:
To disable NTP authentication, use the no ntp authenticate global configuration command. To remove
an authentication key, use the no ntp authentication-key number global configuration command. To
disable authentication of the identity of a device, use the no ntp trusted-key key-number global
configuration command.
This example shows how to configure the switch to synchronize only to devices providing authentication
key 42 in the device’s NTP packets:
Switch(config)# ntp authenticate
Switch(config)# ntp authentication-key 42 md5 aNiceKey
Switch(config)# ntp trusted-key 42
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 ntp authenticate Enable the NTP authentication feature, which is disabled by
default.
Step3 ntp authentication-key number md5 value Define the authentication keys. By default, none are defined.
•For number, specify a key number. The range is 1 to
4294967295.
•md5 specifies that message authentication support is provided
by using the message digest algorithm 5 (MD5).
•For value, enter an arbitrary string of up to eight characters for
the key.
The switch does not synchronize to a device unless both have one
of these authentication keys, and the key number is specified by the
ntp trusted-key key-number command.
Step4 ntp trusted-key key-number Specify one or more key numbers (defined in Step 3) that a peer
NTP device must provide in its NTP packets for this switch to
synchronize to it.
By default, no trusted keys are defined.
For key-number, specify the key defined in Step 3.
This command provides protection against accidentally
synchronizing the switch to a device that is not trusted.
Step5 end Return to privileged EXEC mode.
Step6 show running-config Verify your entries.
Step7 copy running-config startup-config (Optional) Save your entries in the configuration file.