Cisco Systems 3750E manual Configuring NTP Associations

Chapter 7 Administering the Switch

Managing the System Time and Date

	Command	Purpose
Step 3
	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-numbercommand.
Step 4
	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.
Step 5
	end	Return to privileged EXEC mode.
Step 6
	show running-config	Verify your entries.
Step 7
	copy running-config startup-config	(Optional) Save your entries in the configuration file.

To disable NTP authentication, use the no ntp authenticate global configuration command. To remove an authentication key, use the no ntp authentication-keynumber global configuration command. To disable authentication of the identity of a device, use the no ntp trusted-keykey-numberglobal 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

Configuring NTP Associations

An NTP association can be a peer association (this switch can either synchronize to the other device or allow the other device to synchronize to it), or it can be a server association (meaning that only this switch synchronizes to the other device, and not the other way around).

Catalyst 3750-E and 3560-E Switch Software Configuration Guide

OL-9775-02 7-5