Thanks Mohammed,I just configured the core switch to be ntp master , and for all edge switches I write this command: ntp server

Thanks again Mohammed.

Are both the core switch and the access switches set to the same timezone?

Also have you checked the ntp status and associations to make sure that they are communicating correctly?

sh ntp stat

sh ntp ass

Thanks mopple,please find below the output of the sh ntp stat AND sh ntp ass , do you think that it will work now and will not return to the old time after restart or after a certain event ???

Core_SW#sh ntp stat

Internet_Core#sh ntp status

Clock is synchronized, stratum 8, reference is 127.127.7.1

nominal freq is 250.0000 Hz, actual freq is 250.0000 Hz, precision is 2**19

reference time is CA7BAE6C.687555BA (09:46:52.408 EET Sun Aug 26 2007)

clock offset is 0.0000 msec, root delay is 0.00 msec

root dispersion is 15875.02 msec, peer dispersion is 15875.02 msec

Core_SW#

Core_SW#sh clo

Core_SW#sh ntp ass

address ref clock st when poll reach delay offset disp

~10.10.15.1 0.0.0.0 16 - 64 0 0.0 0.00 16000.

*~127.127.7.1 127.127.7.1 7 31 64 1 0.0 0.00 15875.

* master (synced), # master (unsynced), + selected, - candidate, ~ configured

Core_SW#

Core_SW#

Mohammad

Would I be correct in assuming that you configured this switch with the command ntp master?

I am assuming this from the fact that the switch appears to be synced to its own time:

Internet_Core#sh ntp status

Clock is synchronized, stratum 8, reference is 127.127.7.1

If the switch is syncing to its own time then you will still have a problem when the switch reboots because it will lose its own time when it reboots. You need something in your network to sync to something that has a reliable and authoritative time. Frequently this is done by having ntp server command pointing to some device in the public Internet or to some device with a reliable authoritative time source. The 2900 series switches do not fall into this category.

HTH

Rick

Thanks Rick, You are right , as I'm using ntp master for our core switch , as it's connected to a UPS and has redundant power supply, but in all other access switches 2950 are configured using ntp server , the problem is that sometimes I find those 2950 switches return to the old timing like 3 march 1993 , so why this happen although the core switch has the correct date and time ??

Mohammad

If the core switch does have the correct time, and if the remote switch is not learning the correct time from the core switch then I would assume that either there is some connectivity problem between the remote switch and the core or that there is some problem with the configuration of ntp server on the remote switch.

When this problem happens can you see if ping from the remote switch to the core switch succeeds or fails? If ping succeeds then there is connectivity. In that case I would ask that you post the output of the successful ping and post the configuration of the remote switch.

HTH

Rick

Mohammad,

You have Core_SW & Internet_Core so I'm a little confused as to which is the 2950.

I'm presuming the 2950 is 'Internet_Core' but this is using itself as the master. Can you post the ntp parts of the running configs for the two switches with a conformation of which is the 2950.

Mel

sorry it was a mistake by me , the Internet_Core and Core_SW are the same switch , I just was changing the real hostname :) , any way as I wrote before , the configuration I did was a straight forward , I just on the Core Switch made it ntp master , and in all other switches (2950) put this command ntp server

the connection is stable with the core switch , but I don't know why sometime before I find the clock on the 2950 switches not the same as the core even they have been configured with the ntp server command , but I reconfigured them with the same configuration for about 4 days ago and they are OK till now.

Thanks alot for you all..