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New Member

problems in NTP : Network time protocol


i have one 3640 , 2610 , 2924 devices in my LAN .

these devices are not having system clock calender.

I configured my PC (windows 2000 professional) as providng Time service

in LAN. I am not syncing over WAN ,,it is inside my LAN.

I have used just one command in 3640 router after configuring my PC as Time server ,,,

command is as follows .....


Ntp server prefer

! is my PC ip address and is 3640 router's ethernet ip address.

these are connected through Switch 2924

THough i am synchronizing my PC time through internet time servers , but i have enabled w32time service of windows 2000 Pro. and configred it as local time server for my LAN by editing registry keys.

i have not used any other command except ntp server prefer.

Also my router time is in skew of server.

my cisco ios version details ----

Cisco Internetwork Operating System Software

IOS (tm) 3600 Software (C3640-IS40-M), Version 12.0(4)T, RELEASE SOFTWARE (fc1)

Copyright (c) 1986-1999 by cisco Systems, Inc.

Compiled Thu 29-Apr-99 16:01 by kpma

Image text-base: 0x600088F0, data-base: 0x60B56000

ROM: System Bootstrap, Version 11.1(20)AA1, EARLY DEPLOYMENT RELEASE SOFTWARE (f


Head_Office uptime is 2 days, 3 hours, 29 minutes

System restarted by power-on at 10:29:38 ast Mon Aug 26 2002

System image file is "flash:c3640-is40-mz_120-4_T.bin"

cisco 3640 (R4700) processor (revision 0x00) with 28672K/4096K bytes of memory.

Processor board ID 14393449

R4700 CPU at 100Mhz, Implementation 33, Rev 1.0

Bridging software.

X.25 software, Version 3.0.0.

1 Ethernet/IEEE 802.3 interface(s)

5 Serial network interface(s)

DRAM configuration is 64 bits wide with parity disabled.

125K bytes of non-volatile configuration memory.

8192K bytes of processor board System flash (Read/Write)

Configuration register is 0x2102

suggest me what to do ?


  • Other Security Subjects

Re: problems in NTP : Network time protocol

Since there has been no response to your post, it appears to be either too complex or too rare an issue for other forum members to assist you. If you don't get a suitable response to your post, you may wish to review our resources at the online Technical Assistance Center ( or speak with a TAC engineer. You can open a TAC case online at

If anyone else in the forum has some advice, please reply to this thread.

Thank you for posting.

New Member

Re: problems in NTP : Network time protocol

The problem is that most servers only support NTP version 2 where the default version that a cisco router uses is Version 3. use the command:

ntp server version 2 prefer

and that should work, even with w32time services of windows.

New Member

Re: problems in NTP : Network time protocol

The Windows w32time service does not provide ntp server functionality. It only works as an NTP client. You need to either setup a real ntp server on your w2k box, or have one of your routers be an NTP server.

Everything you ever need to know about ntp can be found at:


New Member

Re: problems in NTP : Network time protocol

If your NTP server is working fine, try to use the following command:

ntp server prefer source ethernet

New Member

Re: problems in NTP : Network time protocol

The w32tm service on Windows 2000 / XP does not act as an NTP server, but it does act as an SNTP server. You may be able to configure a cisco router with the following command, depending on version:

sntp server xx.xx.xx.xx

New Member

Re: problems in NTP : Network time protocol


I have a similar situation - I have a centralised W2K Server with stratum 1 Galleon Atomic Radio Clock providing authoritative NTP source.

Local W2K servers use W32Time to sync with the stratum 1 server, and these, in turn, act as stratum 2 servers for network devices connected on the same VLAN. Registry changes have been made to W2K to enable it as an SNTP server.

In this set up, all of our Nokia firewalls and Cisco Catalyst devices (6509s, 6009s, 4003s) sync with their local stratum 2 servers. No problems.

None of our MSFCs can sync though. Debug ntp shows NTP packets correctly being received from the stratum 2 server, but they are ignored. show ntp associations shows that although the server has been configured, it is not recognised as a master (I guess this means authoritative?).

I read somewhere that the routers will only recognise a time source if it is considered authoritative....

With this in mind, I reconfigured some MSFCs to use the stratum 1 authoritative NTP time server and got exactly the same problem! So this problem doesn't appear to be about W32Time and SNTP.

Can someone define what 'authoritative' means in this context, and what an MSFC would look for in an NTP packet to determine this?

Thanks in advance,


New Member

Re: problems in NTP : Network time protocol

I am experiences the same problems. In our environment we use dedicated NTP servers from, that sync to the GPS system. All of our Cisco devices use these servers and they are all able to synchronize, except our MSFC in the 6509s. I've tried using the debug ntp commands, but I am not seeing anything. Please let me know if you find a problem.

New Member

Re: problems in NTP : Network time protocol

I am attempting to configure my MSFC in my 6509 with an NIST NTP server. My show ntp status indicates:

PPMPRouterPRI_1#sh ntp status

Clock is unsynchronized, stratum 16, no reference clock

nominal freq is 250.0000 Hz, actual freq is 250.0000 Hz, precision is 2**24

reference time is 00000000.00000000 (17:00:00.000 MST Wed Dec 31 1899)

clock offset is 0.0000 msec, root delay is 0.00 msec

root dispersion is 0.00 msec, peer dispersion is 0.00 msec

Haven't found anything on CCO that would help me troubleshoot this issue!

New Member

Re: problems in NTP : Network time protocol


I have looked into this issue too, since our routers would allso not sync to a windows box and did to some vms time servers.

The issue as far as i got seems to be the following:

After debugging both situations we saw the error margin from the vms machine on 0.04 after 6 cycles as the windows time source got stuck above 1 even after 12 cycles.

Below 1 the cisco seemed to reset it's own clock and use the time source.

Windows w32time is'nt a reat ntp server but sn sntp server witch is mutch less accurate.

Cisco equiptment seems only to sync if :

Time range is within 4 seconds of source.

Error in time deviation is within 1%.

So "authorative seems to mean accurate"



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