ntp IOS Cisco 4506

I want ot configure all my switches to regularly sync time with a time server.

ntp peer timeserver ntp server timeserver ntp peer timeserver

sh clock

17:22:44.653 UTC Thu Sep 7 2006

Still shows time out of sync.

Do i have to reload for it to sync?

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If you have access control lists, you may need to adjust them to permit the ntp packets through.

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Walter Roberson

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System image file is "bootflash:cat4000-i5s-mz.122-25.EWA5.bin" cisco WS-C4506

R1#sh run | inc ntp

ntp update-calendar ! 4500 has battery backed clock, I think ! so update it from NTP. NOT ESSENTIAL. ntp server prefer ntp server R1#sh ntp ass

address ref clock st when poll reach delay offset disp

+~ x.15.9.3 5 39 64 377 0.8 149.13 3.6 *~ x.15.9.3 4 8 64 377 1.1 164.20 13.4 * master (synced), # master (unsynced), + selected, - candidate, ~ configured

If you added manually anything like ntp clock-period 17179223 delete it. It is computed automatically.

Beware windows 2000 and earlier had some problem with its built in SNTP server and it did not work with Cisco.

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can you ping the NTP server ?

does debug ntp shows NTPpackets being transmittted and received ?

there have been IOS bugs that required removing all of the ntp commands and then re-inputting them in order to getclock sync

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If you had another router you could configure it to be an NTP server.


conf t ntp master 1

R2# ntp server address-of-R1

For example -

R2#sh run | inc ntp server ntp server

R2#sh ntp ass

address ref clock st when poll reach delay offset disp ~ 16 44 64 0 0.0 0.00 16000. * master (synced), # master (unsynced), + selected, - candidate, ~ configured

Note - no association indicated above.

e.g. R1(config)#ntp master 1 R1(config)#^Z R1#sh ntp ass

address ref clock st when poll reach delay offset disp

*~ .LOCL. 0 26 64 377 0.0 0.00 0.0 * master (synced), # master (unsynced), + selected, - candidate, ~ configured R1#

Wait until NTP does it's thing. Best actually to remove and re-install ntp config on R2 otherwise you may have to wait a long time.

R2#sh ntp ass address ref clock st when poll reach delay offset disp

*~ .LOCL. 1 10 64 17 80.2 3.00 1883.9 * master (synced), # master (unsynced), + selected, - candidate, ~ configured R2#

Note that we now have a "master" indicated by "*".

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You are getting time from both time servers. You don't have your timezone set on the switch (it is showing the time in UTC) so maybe you think the time is off because it off by the number of hours from GMT? In any event you should set the timezone properly on the switch. However, if this is not the problem, how far off is the time? If it is off by a couple of hours, it can literally take weeks, for it to sync up properly.

To fix this, set the correct timezone on switch, remove the NTP statements from the config, remove any statements about "clock period", manually set the time on the switch to within a couple of minutes, add the ntp server statements back.

The time should sync up to a few milliseconds within an hour or two.


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Here's from a 2950. Exact same config on the 1605r, too.

clock timezone CST -6 clock summer-time CDT recurring

ntp server ntp server

Me thinks not.

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