[ntp:questions] NTP disregard bogus time from server

Martin Burnicki martin.burnicki at burnicki.net
Wed May 12 09:14:07 UTC 2021


Hi,

Todd Sampson wrote:
> Hi,
> We have an NTP server running on an embedded device that uses IRIG for its time source.  The problem is that if the embedded device boots without an IRIG source, its time is 1970.  When a computer asks our embedded device for the time, the computer's time is set to 1970.  This causes various services to refuse to work.
> 
> Is it possible to set something in the computer's ntp configuration to reject time if it's less than the year 2020 or something similar so that the bogus 1970 time is not believed?

The normal behavior of the server should be that it doesn't claim to be 
synchronized as long as its time source (the IRIG time code, in this 
case) is not available. This means the server should be visible with 
leap bits '3' (11 binary), and stratum 16 in this case.

The normal behavior of an NTP client is that it accepts a time source 
only if the time source claims to be synchronized to "something".

So your client should not accept your server if the server is unable to 
synchronize to an incoming time code.

Which NTP software is running on the server, and which on the client(s)?

Martin

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