07-05-2011 09:38 AM - edited 03-07-2019 01:06 AM
Switch: WS-C3560-48PS-E
IOS: (C3560-IPSERVICESK9-M), Version 12.2(53)SE2
I have the above switch running at a small site; it is configured as the default gateway (10.x.x.1 - has multiple VLANs) and also currently gets its own time from an NTP server across the WAN.
How can I configure this switch so that hosts in this site can get their NTP from it?
Seems I have to configure interfaces, either physical or VLANs, with...
ntp broadcast
...but then don't the hosts have to be able to receive NTP broadcasts? I don't necessarily know what the capabilities of the various hosts are so I can't relay on this functionality it seems. I want the hosts to have whichever 10.x.x.1 set and actively query it for NTP.
Thanks,
jdlampard
07-05-2011 11:21 AM
Hi,
just use the command ntp master on the switch and then put the ip address of the switch on your ntp clients.
Regards.
Alain.
07-05-2011 11:23 AM
Configure the hosts to get their time from the same device you are getting timing for your switch, because
The switch does not have a hardware-supported clock and cannot function as an NTP master clock to which peers synchronize themselves when an external NTP source is not available. The switch also has no hardware support for a calendar. As a result, the ntp update-calendar and the ntp master global configuration commands are not available.
HTH
07-05-2011 11:27 AM
Hi Reza,
I didn't know this fact, thanks for info.
Regards.
Alain.
07-05-2011 02:48 PM
I agree with Reza. I wouldn't configure Cisco appliance as an authoritative NTP server.
If you have Windows servers, you can configure them to be an authoritative NTP server.
How to configure an authoritative time server in Windows XP
http://support.microsoft.com/kb/314054
How to configure an authoritative time server in Windows Server
http://support.microsoft.com/kb/816042
How to configure an authoritative time server in Windows 2000
http://support.microsoft.com/kb/216734
The Cisco appliance don't really have a "clock" per se. They have a battery operated internal clock and it's not synchronized. However, if you let the Cisco appliance synchronize to an authoritative source and use this same appliance to dish out the NTP details, then it's the way to go. I know I have implemented this type of system in several networks.
03-25-2017 05:54 PM
You cannnot configure a 3560 Switch as a NTP Server (Master) itself. It's not supported. Even ntp per interface commands do not work. This is what Cisco says about this:
The switch does not have a hardware-supported clock and cannot function as an NTP master clock to which peers synchronize themselves when an external NTP source is not available. The switch also has no hardware support for a calendar. As a result, the ntp update-calendar and the ntp master global configuration commands are not available.
See the link here: http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3560/software/release/12-2_55_se/configuration/guide/3560_scg/swadmin.html
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