Cisco NTP Server & Windows W32TM

(Originally posted 2015-06-24)

So, I ran into something interesting and confusing today.

I found that my PDC was stuck on ‘Local CMOS Clock’ as it’s source, despite it being configured to use an external NTP server (in this case, my local Cisco router is configured as an NTP server). Finding this odd, I verified the configuration and then executed a resync command:
w32tm /resync
and received this output:
Sending resync command to local computer
The computer did not resync because no time data was available.
Curious, as the NTP server is running and other devices are syncing correctly. Logging into the Cisco router and executing ‘show ntp associations’ resulted in this:
 address         ref clock       st   when   poll reach  delay  offset   disp
  192.168.1.11    .INIT.          16      –  32768     0  0.000   0.000 15937.
  192.168.1.12    .INIT.          16      –  32768     0  0.000   0.000 15937.
 ~2610:20:6F15:15::27
                  .STEP.          16      –   1024     0  0.000   0.000 15937.
*~128.138.140.44  .NIST.           1      2     64   377 44.098   0.552  3.122
Well, that’s odd. The system is syncing correctly, but why are the domain controllers showing up as stratum 16?
‘show ntp associations detail’
192.168.1.11 dynamic, insane, invalid, unsynced, stratum 16
ref ID .INIT., time 00000000.00000000 (16:00:00.000 PST Wed Dec 31 1899)
our mode passive, peer mode unspec, our poll intvl 32768, peer poll intvl 131072
root delay 0.00 msec, root disp 0.00, reach 0, sync dist 15956.69
delay 0.00 msec, offset 0.0000 msec, dispersion 15937.50
precision 2**24, version 3
Well, that’s not good, it’s trying to register itself as an NTP peer with the Cisco router. Googling some bits finally led me to a bug report between certain versions of Cisco IOS and W32Time.
The fix?
Change the w32time configuration:
w32tm /config /manualpeerlist:IPADDRESS,0x8 /syncfromflags:manual /reliable:yes /update
net stop w32time && net start w32time
w32tm /resync
That ‘0x8’ allows it to work.

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