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From: [email protected] 
[[email protected]] On Behalf Of Todd Hodgen 
[[email protected]]

I’m wanting to run a sipXecs system without internet access, or access to an 
external NTP server for Demonstration purposes.   Does anyone know a way to 
work around the need for an NTP server, and keep the time from flashing on end 
devices.  Without an NTP server, the boot process for Polycom phones is delayed 
as they look for NTP source, and when they come up, the clock flashes on them 
annoyingly.
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Set up an NTP server on some computer within the LAN, probably sipX.  Configure 
it to "synchronize to the local clock" if it cannot access an authoritative 
server.  This involves something like the following lines in /etc/ntpd.conf:

# Undisciplined Local Clock. This is a fake driver intended for backup          
# and when no outside source of synchronized time is available.                 
server 127.127.1.0     # local clock                                           
fudge  127.127.1.0 stratum 10                                                  

Use this NTP server as you otherwise would -- everything will sync to it.

One problem with "local clock" use is that the frequency of local clocks is not 
very accurate, although their frequency tends to be very consistent.  So your 
time will drift away from real time by as much as a minute a day.  The way to 
get around that is to have the NTP server calculate the rate of drift and 
compensate for it.  Add this to ntpd.conf:

driftfile /var/lib/ntp/drift

Then connect the system to the Internet and tell NTP about an authoritative 
server.  In that configuration, NTP will calcuate and save the difference 
between the local clock frequency and real time, and save the value in the 
"drift file".  Then when you boot the system disconnected from the Internet, 
NTP will tweak the local clock to run very close to true frequency.  Of course, 
you can't set the time from your watch better than a minute from real time, but 
at least the computer's clock won't drift off.

Dale
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