Cisco Catalyst 4500 series Administration Manual page 173

Chapter 4 Administering the Switch
Command
Step 4
ntp trusted-key key-number
Step 5
end
Step 6
show running-config
Step 7
copy running-config startup-config
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# configure terminal
Switch(config)# ntp authenticate
Switch(config)# ntp authentication-key 42 md5 aNiceKey
Switch(config)# ntp trusted-key 42
Switch(config)# end
Switch#
OL-30933-01
Purpose
Specifies 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.
Returns to privileged EXEC mode.
Verifies your entries.
(Optional) Saves your entries in the configuration file.
Software Configuration Guide—Release IOS XE 3.6.0E and IOS 15.2(2)E
Managing the System Time and Date
4-5