NTP not synchronising

[mohammed hurais]

Hi guys..

I got a issue with NTP synchronization.

We got a scenario like this

access switches-->dist switch --> ntp server

dist switch is synchronized with server

but all the access layer switches are not getting synchronized... on access layer switch we got authentication...is authentication required on dist switch also?

can any one pls help???????????

[cadet alain]

Hi,

on the NTP clients( the access switches) you can authenticate the server( your distribution switch) so you must set the authentication key on the distribution switch.

here is  how to do it:

http://blog.ine.com/2007/12/28/how-does-ntp-authentication-work/

look at case 4 where R2 is the server and R1 a client

Regards

Alain

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[mohammed hurais]

Hi cadet

On dist and access switch i got conf as

ntp server x.x.x.x

on access switch

ntp server x.x.x.x key 1 prefer

ntp server x.x.x.x                   /we got two dist switches so 1st one is preferred/

ntp authentication-key 1 md5 xxxxx

ntp trusted-key 1

still its not updating...

actually when i do show ntp association its showing unsync,invalid

[Leo Laohoo]

My suggestion is to take off all the "silly" stuff, like authentication, and see what happens.

A simple "ntp server

Another thing, what's your NTP server?  Is it a GPS-enabled appliance or is it one of those appliance that need access to the internet?

[mohammed hurais]

NTP server we are using is windows AD server...and i guess its using SNTP packets..

[cadet alain]

Hi,

I don't see the ntp master command on the dist switch, you must add it and like leo suggested get rid of auth on clients first and also make sure that the clocks of the clients are not too far away from the distribution clock otherwise it will take ages to sync.

Regards

Alain

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[mohammed hurais]

Hi  cadet..

i tried removing all the authentication commands..still its not syncrzng...

rregarding  Master command ...dist switch is already synced with ntp server and ntp association is successfull on this switch..if i add master cmnd.....wont this affect any thing on dist switch?

Also this is a production network..i have to make sure it wont affect any thing....

[cadet alain]

Hi,

for a client-server relationship as the access have the distribution switch as a server then on this switch you must set it as a server with the ntp master command.

Regards

Alain

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[George Stefanick]

Yea, I just had issues using WIndows server as SNTP with our Cisco gear. Normally, folks will SYNC their core with a outside NTP server and then make it master. Then sync all other gear with it ..

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[Leo Laohoo]

NTP server we are using is windows AD server

Windows AD????

If I recall, windows does not know how to "talk" NTP. 

[mohammed hurais]

NTP server hosted on windows.......it uses SNTP