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NTP problem on C3750X-24S 15.0(1)SE3



We have a new backbone in our LAN with two C3750X-24S 15.0(1)SE3. Since we change the model of our equipement we can't update NTP on this two switchs.

We try to update NTP with two firewall Juniper SSG-140 in version 6.3.0r12.0. The two switchs never arive to associate with firewall (we try with the comme ntp server and ntp peer)

So we configure ntp server on our distribution servers switchs (one 4900 12.2(54)SG and one stack of 3750G and 3750E 12.2(50)SE5). They have no problem to update NTP on the firewal.So we change our configuration ntp server on the backbone and we try to update it with the distributions servers switchs.

With the command ntp server it doesn't work.

With the commande ntp peer it works but not everytime. The core switchs are in "synchronized" state then "unsynchronized" then "synchronized" etc...

When they are in "unsynchronized" state there is "x falseticker" raison behind the IP of the ntp peer.

Do you know this probleme? Is it an IOS version problem on our core switch?

Thanks in advance


6 Replies 6

Leo Laohoo
VIP Community Legend VIP Community Legend
VIP Community Legend

For the 15.0(X), it takes exactly 10 minutes for the NTP to sync.

Thanks for your answer

But the problem is that the two cores switchs are synchronized and then unsynchronized and then synchronized etc... without doing anything.

I think once they are synchronized i shouldn't see them doing: unsynchronized, synchronized, unsynchronized, synchronized...

Configure your core switches to go out to the internet to get their NTP synchronize.

If not, then you may think of getting a "true" NTP server. 

I can't configure to the internet it isn't the policie of my client.

We already have a true NTP server and it is behind the firewall so that why we want to synchronise the core with the firewall

So your core is trying to sync with this NTP server?


Actually i just try to synchronise ntp on the 2 3750X-24S with 2 cisco equipements:

One is a 4900 in  version 12.2(54)SG

The second is a stack of 3750 (G and E) in version 12.2(50)SE5

and the result is that:

XX-XX-1#sh ntp status

Clock is unsynchronized, stratum 16, no reference clock

nominal freq is 119.2092 Hz, actual freq is 119.2152 Hz, precision is 2**17

reference time is D4BCAFA2.80783732 (11:32:02.501 WET Wed Feb 6 2013)

clock offset is 0.0000 msec, root delay is 0.00 msec

root dispersion is 11.64 msec, peer dispersion is 0.00 msec

loopfilter state is 'CTRL' (Normal Controlled Loop), drift is -0.000050098 s/s

system poll interval is 64, last update was 1291 sec ago.

XX-XX-1#sh ntp associations

  address         ref clock       st   when   poll reach  delay  offset   disp

x~     2     42     64   377  1.103 551.056  3.319

x~     2      7     64   377  1.402  -1.523  3.952

* sys.peer, # selected, + candidate, - outlyer, x falseticker, ~ configured

It doesn't work.

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