Cores Distribution Switch as NTP server

[maraica]

Can I add the core switch to be NTP server for the rest of the switches 3850.  

What is best practice:  create one of the switches to serve as the NTP server or to point every single switch to the public external NTP server?

thanks

[Alex Pfeil]

The best practice is to have two devices as NTP servers and then point all devices to those two devices for NTP.

Please mark helpful posts.

[maraica]

Thanks,

I currently point the NTP to ntp server 66.80.130.90 66.80.130.54 (I believe these from Caltech California).  Is there a more reliable or more common ntp server to point to?

thanks

[Reza Sharifi]

Hi,

If you are looking for public NTP, you can use pool.ntp.org 

Have a look:

https://www.pool.ntp.org/zone/@

HTH

[dbeattie]

I have always gone for at least three NTP sources/servers because if two sources diverge slowly, the client has little chance of working out which one is wrong. In fact, I usually have four internal switches that peer with each other to arbitrate time. Each one of these takes a time source from four different Internet sources from pool.ntp.org (a total of 16 sources). Internal clients use as many of the four switches as they can. You can also set up a VIP (e.g. HSRP) between switches for clients that can only support one NTP source address.

Please also remember to set the relevant access lists on the switches to ensure that clients cannot affect the time on the switches.

Hope this helps

Dave

[Leo Laohoo]

Can be done.
IMPORTANT: Don't use the command "ntp master".
Make sure your core switch is synchronized against a "trusted" NTP server, preferably one with very low stratum number.
So, if the core is synchronized, point the distribution switches to the core.
Point all the access switches to the distro switches.
Get it?

[maraica]

If NTP master is not to be used, what will be right commands to set the ntp server?

thank you

[Leo Laohoo]

Keep it simple: ntp server <SERVER IP ADDRESS> [prefer]

[maraica]

Awesome!  Thanks