NTP Setup Issues in Home Lab

Answered Question
Jun 21st, 2008
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Hi Everyone,


Can anyone give me some information on setting up NTP in a home lab - I have been trying to get it working forever, but nothing seems to work.


I have three 3640 routers and a Win laptop connected to a Catalyst switch. Using the "ip helper-address" and "ip forward-protocol" commands, I have successfully configured the laptop as a SNMP server and as a tftp server and achieved communication with all 3 routers. I have never, however, gotten NTP functioning.


On the laptop, I've downloaded Nettime, Meinberg Network Time Protocol, NTP Time Server Monitor and done a lot of research on the IOS commands, but have never had a router receive the correct time from my pc.


Can anyone point me in the right direction or shed some light on what I may be doing wrong, or if I can use a laptop as an NTP server for my routers. Also - what program would you recommend?


Thanks in advance!


Sincerely,

Jim Woodward

Correct Answer by Richard Burts about 8 years 9 months ago

Jim


The principal problem with trying to use a Windows machine as an NTP server is that Windows uses a simplified time protocol and not actual NTP. But running something like Meinberg should get around that. If the routers are not learning time from the laptop my first guess would be that something is wrong with the Meinberg install or it is not running correctly.


If you believe that Meinberg is running correctly then there is a possibility that there is an issue with the NTP configuration of the routers. If you would post the NTP config from the routers that might help. It might also be helpful if you would post the output of show ntp association detail from at least one of the routers.


HTH


Rick

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Correct Answer
Richard Burts Sat, 06/21/2008 - 11:44
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Jim


The principal problem with trying to use a Windows machine as an NTP server is that Windows uses a simplified time protocol and not actual NTP. But running something like Meinberg should get around that. If the routers are not learning time from the laptop my first guess would be that something is wrong with the Meinberg install or it is not running correctly.


If you believe that Meinberg is running correctly then there is a possibility that there is an issue with the NTP configuration of the routers. If you would post the NTP config from the routers that might help. It might also be helpful if you would post the output of show ntp association detail from at least one of the routers.


HTH


Rick

jamesawoodward Sat, 06/21/2008 - 13:23
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Hi Rick,


Thank you so much for your help. I had wiped the configs on the routers clean to follow along with some other exercises. So I just set the network back up to run NTP, and started troubleshooting at the PC first. I discovered that the Network Time Protocol Daemon service was not running, and would start and then stop immediately. I resolved this when I closed NetTime. So once I had the protocol up and running, and was syncing my ntp server from various internet servers, I turned on the router, configured ip addresses, confirmed connectivity back and forth by pinging, and configured "ntp server 172.16.9.4" on the router. but nothing.


So I checked my Windows Firewall to make sure that UDP port 123 was open, and . . . well . . . I discovered that it wasn't. So after opening that port in my firewall (which I really thought I had done before) - here are my results:

Bottom#sho ntp assoc detail

172.16.9.4 configured, our_master, sane, valid, stratum 2

ref ID 192.43.244.18, time CC07EEFB.94875897 (21:19:55.580 UTC Sat Jun 21 2008)

our mode client, peer mode server, our poll intvl 64, peer poll intvl 64

root delay 69.49 msec, root disp 54.17, reach 377, sync dist 90.439

delay 2.15 msec, offset 5.8355 msec, dispersion 0.46

precision 2**18, version 3

org time CC07EF5C.5324FB77 (21:21:32.324 UTC Sat Jun 21 2008)

rcv time CC07EF5C.51ED6AE4 (21:21:32.320 UTC Sat Jun 21 2008)

xmt time CC07EF5C.515D4270 (21:21:32.317 UTC Sat Jun 21 2008)

filtdelay = 2.15 2.32 2.14 2.27 3.68 2.27 2.30 2.17

filtoffset = 5.84 5.89 4.77 6.00 4.16 5.84 4.72 4.52

filterror = 0.02 0.99 1.97 2.94 3.92 4.90 5.87 6.85


Bottom#sho ntp status

Clock is synchronized, stratum 3, reference is 172.16.9.4

nominal freq is 250.0000 Hz, actual freq is 249.9998 Hz, precision is 2**18

reference time is CC07EF5C.51ED6AE4 (21:21:32.320 UTC Sat Jun 21 2008)

clock offset is 5.8355 msec, root delay is 71.64 msec

root dispersion is 60.46 msec, peer dispersion is 0.46 msec



Richard Burts Sat, 06/21/2008 - 14:06
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Jim


I am glad that my suggestions got you going in the right direction. And I would say that it was pretty good troubleshooting on your part to discover the dependency (or negative dependency) between NTP and NetTime. And the issue with the firewall was good logical troubleshooting.


Thank you for using the rating system to indicate that your problem was resolved (and thanks for the rating). It makes the forum more useful when people can read about a problem and can know that they will see what did resolve the problem.


The forum is an excellent place to learn about Cisco networking. I encourage you to continue your participation in the forum.


HTH


Rick

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