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NTP - Catalyst Switches taking 5-15 Minutes to Sync with NTP Server

Hi All,

In the concerned network two Cat8540MSR switches are configured as NTP servers, one is preferred. Many Cat 8540MSR, Cat5500, Cat3500 switches and 1700 routers are configured as NTP clients. All are synchronised. Now to demonestrate the NTP functionality, I manually change system time of the primary NTP server (Cat8540MSR). Now the NTP clients are taking different time to synchronise with the NTP Server. Its observed that one Cat8540MSR configured as NTP client took 16 minutes to synchronised. Others took 2 to 10 minutes. Can anybody suggest why clients are taking so long to synchronise and why synchronisation time is also differing? Can this be set to some predetermined value?

Regards & thanks in advance,



Re: NTP - Catalyst Switches taking 5-15 Minutes to Sync with NTP

I haven't looked at this for a while, so I'm not clear on the details ...

My recollection of NTP is that it is not a "one shot" time correction. By using a series of readings, the latency of the links (time server --> time client) can be assessed and compensation, if necessary, can be applied.

The effect (if I am recalling correctly) is that the time is "slowly adjusted" into sync with the time servers(s) according to stratum level, preference, distance / link latency, etc.

The longer the client is online and communicating to a constellation of servers, the more accurate / in-sync the time should be, especially with stable links.



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