ntp synchronization

USAlliance
USAlliance used Ask the Experts™
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Headquater router 2811 using PST and branch router 2811 using EST. I configured to synchronize time and pc and phones will use PST time from HQ. Here is my configuration. How could I verify branch router get PST? PC connected branch router still EST.

HQ
scheduler allocate 20000 1000
ntp master 2
ntp peer 10.10.11.40
ntp peer 10.10.11.20

HQ#sh ntp status
Clock is synchronized, stratum 2, reference is 127.127.7.1
nominal freq is 250.0000 Hz, actual freq is 250.0000 Hz, precision is 2**18
reference time is CFD9EB82.4A2B5B03 (10:01:54.289 PDT Sat Jul 3 2010)
clock offset is 0.0000 msec, root delay is 0.00 msec
root dispersion is 0.02 msec, peer dispersion is 0.02 msec

HQ#sh ntp associations
      address         ref clock     st  when  poll reach  delay  offset    disp
 ~10.10.11.40      0.0.0.0          16     -  1024    0     0.0    0.00  16000.
*~127.127.7.1      .LOCL.            1     3    64  377     0.0    0.00     0.0
 ~10.10.11.20      10.10.30.1        3  8773  1024    0     8.7    0.06  16000.
 * master (synced), # master (unsynced), + selected, - candidate, ~ configured

Branch Router
scheduler allocate 20000 1000
ntp clock-period 17179963
ntp peer 10.10.11.40
ntp server 10.10.30.1
ntp peer 10.10.11.20

SRST-BR1#sh ntp status
Clock is unsynchronized, stratum 16, no reference clock
nominal freq is 250.0000 Hz, actual freq is 249.9986 Hz, precision is 2**18
reference time is CFD9C8E5.183BBE1A (10:34:13.094 EDT Sat Jul 3 2010)
clock offset is 0.0000 msec, root delay is 8.83 msec
root dispersion is 0.11 msec, peer dispersion is 0.06 msec
SRST-BR1#

SRST-BR1#show ntp associations

      address         ref clock     st  when  poll reach  delay  offset    disp
 ~10.10.11.40      127.127.7.1       2  8983    64    0     8.7    0.00  16000.
 ~10.10.30.1       127.127.7.1       2  9181    64    0     8.8   -0.01  16000.
 ~10.10.11.20      0.0.0.0          16     -    64    0     0.0    0.00  16000.
 * master (synced), # master (unsynced), + selected, - candidate, ~ configured
SRST-BR1#
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Top Expert 2010

Commented:
>branch router 2811 using EST
>How could I verify branch router get PST? PC connected branch router still EST.

Well, for one, NTP has nothing to do with timezones; NTP was designed to produce a clock offset, roundtrip delay and dispersion which are relative to a selected reference clock.

http://www.cisco.com/en/US/docs/ios/12_3t/fun/command/reference/cfrgt_01.html#wp1099863
http://oreilly.com/catalog/hardcisco/chapter/ch10.html

something like:

clock timezone CST -6
clock summer-time CDT recurring
clock calendar-valid
clock set 13:21:00 July 3 2010

Billy
Commented:
rfc1180 is right:  You will need to configure the timezone for each router (and also the timezone for each PC and phone) to ensure it displays correctly.

NTP distribute a time-code relative to UTC (previously known as GMT), and does not transmit time zone or daylight savings time information.

One thing I noticed:  You have three NTP peers: HQ is one, and 10.10.11.20 and 10.10.11.40 are the two others.  However, you also configured the last two as peers to the branch router.  But is seems that there is clock-discrepancies between the devices, and therefore not one of them is acceptable to the branch router.

If you cannot source your clock from a valid source (such as a GPS time receiver or an Internet based server) I'd suggest that you choose one source as the master, and sync all others to that device.  For redundancy, you can implement a second server, but just ensure that the second server also sync from the master, and when the master falls away, that it have a less-preferable stratum than the master, but higher than 15. ('ntp master 5' or so should work).

Author

Commented:
I have still time issued PC and Phone connected to Branch router, not get PST time from HQ side.
Below is modified configuration.

clock timezone PST -8
clock summer-time PDT recurring
ntp master 5
ntp peer 10.10.11.40
ntp peer 10.10.11.20
ntp server 10.10.30.121
HQ#sh ntp status
Clock is synchronized, stratum 5, reference is 127.127.7.1
nominal freq is 250.0000 Hz, actual freq is 250.0010 Hz, precision is 2**18
reference time is CFE0C50C.189F464E (14:43:40.096 PDT Thu Jul 8 2010)
clock offset is 0.0000 msec, root delay is 0.00 msec
root dispersion is 6.42 msec, peer dispersion is 6.42 msec
HQ#show ntp ass
HQ#show ntp associations

      address         ref clock     st  when  poll reach  delay  offset    disp
 ~10.10.11.40      0.0.0.0          16     -  1024    0     0.0    0.00  16000.
*~127.127.7.1      127.127.7.1       4    54    64  377     0.0    0.00     0.0
+~10.10.11.20      127.127.7.1       5   110   128  377     8.9   -8.54     0.2
 ~10.10.30.121       0.0.0.0          16     -  1024    0     0.0    0.00  16000.
 * master (synced), # master (unsynced), + selected, - candidate, ~ configured



clock timezone est -5
clock summer-time est recurring
ntp master 5
ntp peer 10.10.11.40
ntp server 10.10.30.121


BR1#sh ntp status
Clock is synchronized, stratum 5, reference is 127.127.7.1
nominal freq is 250.0000 Hz, actual freq is 250.0000 Hz, precision is 2**18
reference time is CFE0C547.23C2839B (17:44:39.139 est Thu Jul 8 2010)
clock offset is 0.0000 msec, root delay is 0.00 msec
root dispersion is 6.39 msec, peer dispersion is 6.39 msec

BR1#sh ntp associations

      address         ref clock     st  when  poll reach  delay  offset    disp
+~10.10.11.40      127.127.7.1       5    75  1024  276     8.7    8.65     2.1
*~127.127.7.1      127.127.7.1       4    19    64  377     0.0    0.00     0.0
 ~10.10.30.121      10.10.11.20       4   639  1024  377     8.8    8.78     1.4
 * master (synced), # master (unsynced), + selected, - candidate, ~ configured
BR1#
Commented:
Again, both routers use themselves as reference clock, as both are configured at the same stratum level.  Configuring these routers as peers will not force them to run the same clock.  I'd suggest that you configure 'ntp master 7' on the branch office, as this will force the branch router to accept the HQ router as source, as long as it is available.

You might also want to include 'ntp update-calendar' on the branch router (if available), as this should keep your branch router's hardware clock synchronised with HQ, and you should not see big changes in timing when the HQ router goes offline.

Author

Commented:
Thank you very much.
 I modified stratum as 7 to ntp master and update-calendar on Branch router.
Now Clock is synchronized, stratum 6 reference is 10.10.11.40.

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