Setting 3750 to be NTP Server

Answered Question
Aug 24th, 2009
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I have a contained environment where I just want my servers all to have the same time. I want them to pull that time from my 3750. What do I have to enable on the 3750 to be the NTP clock source.

Keep in mind that the 3750 will not be getting the source from anywhere else, just my "set clock" command.


Correct Answer by a-moseley about 7 years 10 months ago

3750 switches do not have a hardware clock so cannot be configured to be NTP Master. In similar situations I have connected an otherwise disused Cisco Router which does have such capabilities.

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Overall Rating: 5 (1 ratings)
Lucien Avramov Mon, 08/24/2009 - 10:51
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For the 3750 to be a clock source you need : ntp master 2.

The stratum 1 should be used only if you are using a GPS clock.

So here in this example it's stratum 2.

Also you need ntp source interface X/X if you want to use a specific interface for sourcing ntp.

On the other devices, use the ntp server a.b.c.d where a.b.c.d is the ip address of the 3750.

jfraasch Mon, 08/24/2009 - 11:12
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What is the actual command?

I put in NTP MASTER and get an unrecognized command. I am going through Cisco docs and can't find anything on this.


Lucien Avramov Mon, 08/24/2009 - 11:58
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Its working on my 3750. Are you in config mode?

SW1#show version

Cisco IOS Software, C3560 Software (C3560-ADVIPSERVICESK9-M), Version 12.2(44)SE5, RELEASE SOFTWARE (fc2)

Copyright (c) 1986-2009 by Cisco Systems, Inc.

Compiled Thu 22-Jan-09 05:47 by gereddy

Image text-base: 0x01000000, data-base: 0x02900000

ROM: Bootstrap program is C3560 boot loader

BOOTLDR: C3560 Boot Loader (C3560-HBOOT-M) Version 12.2(44)SE5, RELEASE SOFTWARE (fc2)

SW1 uptime is 13 weeks, 3 days, 17 hours, 30 minutes

System returned to ROM by power-on

System image file is "flash:/c3560-advipservicesk9-mz.122-44.SE5.bin"

This product contains cryptographic features and is subject to United

States and local country laws governing import, export, transfer and

use. Delivery of Cisco cryptographic products does not imply

third-party authority to import, export, distribute or use encryption.

Importers, exporters, distributors and users are responsible for

compliance with U.S. and local country laws. By using this product you

agree to comply with applicable laws and regulations. If you are unable

to comply with U.S. and local laws, return this product immediately.

A summary of U.S. laws governing Cisco cryptographic products may be found at:

If you require further assistance please contact us by sending email to

[email protected].

cisco WS-C3560-24TS (PowerPC405) processor (revision E0) with 131072K bytes of memory.

Processor board ID CAT1114RK0S

Last reset from power-on

1 Virtual Ethernet interface

24 FastEthernet interfaces

2 Gigabit Ethernet interfaces

The password-recovery mechanism is enabled.

512K bytes of flash-simulated non-volatile configuration memory.

Base ethernet MAC Address : 00:1B:8F:F7:B5:80

Motherboard assembly number : 73-9897-06

Power supply part number : 341-0097-02

Motherboard serial number : CAT11145KLR

Power supply serial number : AZS110721FN

Model revision number : E0

Motherboard revision number : B0

Model number : WS-C3560-24TS-S

System serial number : CAT1114RK0S

Top Assembly Part Number : 800-26160-02

Top Assembly Revision Number : E0

Version ID : V02

CLEI Code Number : COMMG00ARB

Hardware Board Revision Number : 0x01

Switch Ports Model SW Version SW Image

------ ----- ----- ---------- ----------

* 1 26 WS-C3560-24TS 12.2(44)SE5 C3560-ADVIPSERVICESK9-M

Configuration register is 0xF

SW1#conf t

Enter configuration commands, one per line. End with CNTL/Z.

SW1(config)#ntp ?

access-group Control NTP access

authenticate Authenticate time sources

authentication-key Authentication key for trusted time sources

broadcastdelay Estimated round-trip delay

clock-period Length of hardware clock tick

logging Enable NTP message logging

max-associations Set maximum number of associations

peer Configure NTP peer

server Configure NTP server

source Configure interface for source address

trusted-key Key numbers for trusted time sources

If the ntp command is not showing like on my switch, you may need an ip services image or higher.

jfraasch Tue, 08/25/2009 - 04:19
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I get the list of commands but it doesnt allow me to set it as a master. If I want it to be the NTP server then how do I make it that? And can I do it if it is only using its own clock to server NTP time?


Correct Answer
a-moseley Tue, 08/25/2009 - 07:59
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3750 switches do not have a hardware clock so cannot be configured to be NTP Master. In similar situations I have connected an otherwise disused Cisco Router which does have such capabilities.

Christian Isla Wed, 09/17/2014 - 06:22
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I'm running a 3750x as well as a 2960x.  with ios15-universal.  They both have 'ntp master'.  ios 12 does not support it..


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