Cisco Systems 3750E manual Configuring NTP Access Restrictions, Ntp broadcastdelay microseconds

Chapter 7 Administering the Switch

Managing the System Time and Date

	Command	Purpose
Step 5
	ntp broadcastdelay microseconds	(Optional) Change the estimated round-trip delay between the switch and
		the NTP broadcast server.
		The default is 3000 microseconds; the range is 1 to 999999.
Step 6
	end	Return to privileged EXEC mode.
Step 7
	show running-config	Verify your entries.
Step 8
	copy running-config startup-config	(Optional) Save your entries in the configuration file.

To disable an interface from receiving NTP broadcast packets, use the no ntp broadcast client interface configuration command. To change the estimated round-trip delay to the default, use the no ntp broadcastdelay global configuration command.

This example shows how to configure a port to receive NTP broadcast packets:

Switch(config)# interface gigabitethernet1/0/1

Switch(config-if)#ntp broadcast client

Configuring NTP Access Restrictions

You can control NTP access on two levels as described in these sections:

•Creating an Access Group and Assigning a Basic IP Access List, page 7-8

•Disabling NTP Services on a Specific Interface, page 7-10

Creating an Access Group and Assigning a Basic IP Access List

Beginning in privileged EXEC mode, follow these steps to control access to NTP services by using access lists:

	Command	Purpose
Step 1
	configure terminal	Enter global configuration mode.
Step 2
	ntp access-group {query-only	Create an access group, and apply a basic IP access list.
	serve-only serve peer}	The keywords have these meanings:
	access-list-number
		• query-only—Allows only NTP control queries.
		• serve-only—Allows only time requests.
		• serve—Allows time requests and NTP control queries, but does not
		allow the switch to synchronize to the remote device.
		• peer—Allows time requests and NTP control queries and allows the
		switch to synchronize to the remote device.
		For access-list-number, enter a standard IP access list number from 1
		to 99.

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

7-8 OL-9775-02