Changing the NTP server under Windows

gpanther — Sun, 19 Oct 2008 17:42:00 +0000

Disclaimer: I’m not a Sysadmin and I’m especially not a Windows/Active Directory sysadmin. From what I’ve know, there is some overlap between this and the AD stuff (in the sense that the DC also provides time info AFAIK, so please also check that possibility if it applies). As always, feedback is welcome.

Setting up NTP under Windows if you want to use a different server than the one provided by MS can be rather tricky. I’ve managed to do it via the following steps:

Ensure that you have the correct time zone set. You can do this either via the control panel or via the command line the following way (of course, change the string as necessary):
```
control.exe timedate.cpl,,/Z (GMT+02:00) Athens, Bucharest, Istanbul
```
Set the NTP server:
```
net time /setsntp:ntp.example.com
```
Make sure that the w32time service is started at system startup. Attention to the space after the equals (=) sign! Due to some dubious reasons, the sc programs needs it that way:
```
sc config w32time start= auto
```

Restart the service and it should automatically synch:

net stop w32time
net start w32time
w32tm /resync /nowait

If you are still having problems (firewalls filtering packets, etc) you may want to try doing a traffic capture with Wireshark (with a filter like “port 123” – because port 123 is for NTP) and analyze it (are packets being sent? are packets being received?).

Update: I’ve seen a Word document floating around the Internet which describes a lot of possible problems and their solutions with the w32time/NTP service, but I just can’t seem to find it any more. If somebody could put provide the link to it, I would be grateful (since it provides much more detailed info than this short post).

Whos timeserver are you using?

gpanther — Sun, 18 Feb 2007 17:14:00 +0000

There was a controversy some time ago involving D-Link and Poul-Henning Kamp where the former were using the timeserver set up by the later as default in their routers, effectively generating a DDoS on the server without giving any recompensation for it. The matter was amically resolved in the end, but it seems that corporations didn’t learn anything from it. I was browsing today through the configuration of an Edimax router and much to my surprise I saw the default timeserver being set to 192.43.244.18, which seems to be a timeserver at the University of Michigan (judging from the partial reverse DNS). I doubt that they have any agreement with Edimax!

Now for the question of which NTP server to use? You can use pool.ntp.org which resolves in a round-robin way to NTP servers which are voluntarily publicly available. There are also subsets available by continents and by country, so that you can choose a server which is nearest to you and use the other servers as fallback. To get a more detailed description, visit the pool.ntp.org website. And make sure that you check your routers default settings!

PS. Some el-cheapo routers (like this Edimax) do not allow the setting of NTP servers by name, only by IP. In this case you should use nslookup to randomly choose a server from the pool and set it as your NTP server.

ntp – Grey Panthers Savannah

Changing the NTP server under Windows

Whos timeserver are you using?