Hi,
My ntp is set to work against a couple of sources, 4 for that matter.
I had a issue when the server I was synchronized with had a problem and started "running" forward in time and my machine synchronized on the faulty time.

Mean while, I had 3 servers marked as backup wich did nothing and then lost sync because the difference was too high.
How to configure the ntp so that the client server will drop the exceptional server even though its is currently the primary ntp source?

Thanks ahead,
Ilia.

NTP should in theory drop any servers that go out of sync with the rest, there are however some things that work against that.

Avoid using servers from a different stratum, the lower stratum servers will have more sway over the higher ones.

Another factor is the network link between you and each server (results in various parameters) better servers link wise will be preferred over others.

Thanks for the answear.

Is it possible from the client side to force all ntp server, regardless of thier staratum, to be considered as in the same stratum ?

I don't think so. The stratum levels are identified within the message. They are used to provide the hierarchy of time references (in a tree). The lower the stratum level the more systems that server provides the time for and is closer to the hardware clock, and should be more reliable. The higher the stratum level, the farther from the time reference it is.

Hence, the use of a GPS clock reference as a stratum 1 server. The server is stratum 1, and the GPS clock itself is stratum 0 (it is the clock reference).

You can get a stratum 1 server for about $200, it does use GPS signals to get the clock time.