Hi All

I have two domain controllers ( Windows 2008 r2 SP1 ) in my environment.


All my linux machines have NTP configured to synchronize time from those domain controllers:

ntp.conf example
server domaincontroller1
server domaincontroller2

This configuration is working fine by years, althought windows team upgrade domain controllers from Windows 2003 to Windows 2008 r2 SP1 and from that point in time I start to get the following messages in my all linux machines ( incluing ESX'i machines ):

messages-20130407:Apr 4 07:19:03 hostname ntpd[1466]: no servers reachable
messages-20130407:Apr 4 07:19:08 hostname ntpd[1466]: synchronized to xxxxxxxx, stratum 2
messages-20130407:Apr 6 00:00:42 hostname ntpd[1466]: no servers reachable
messages-20130407:Apr 6 00:00:44 hostname ntpd[1466]: synchronized to xxxxxxxx, stratum 2
messages-20130407:Apr 6 05:08:05 hostname ntpd[1466]: synchronized to xxxxxxxx, stratum 3
messages-20130407:Apr 6 05:59:14 hostname ntpd[1466]: synchronized to xxxxxxxx, stratum 3
messages-20130414:Apr 7 05:19:28 hostname ntpd[1466]: no servers reachable
messages-20130414:Apr 7 05:53:37 hostname ntpd[1466]: synchronized to xxxxxxxx, stratum 3
messages-20130414:Apr 8 08:04:38 hostname ntpd[1466]: no servers reachable


I already upgrade NTPD to the last version, put just one domain controller in the ntp.conf and I get allways the error "no servers reachable". I'am almost 99% shure that I have no network problem's between the servers.

Any idea where to look ?

Best regards

well it does look like network to me in the first instamce. It looks like you would probably get an insight from running a tcpdump and capturing all traffic on port 123 for a day, then you'll see if the servers are not responding, or responding with unusable replies.

run "tcpdump port 123 -s0 -i eth0 -w ntp_capture.cap" (presumign eth0 is correct) and then inspect it in wireshark afterwards.

Hi Acid

ok I will give it a try, but is a shot in the dark I have no network errors:

Kernel Interface table
Iface MTU Met RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg
eth0 1500 0 163591966 0 0 0 137096834 0 0 0 BMRU
eth1 1500 0 69346077 0 0 0 23171963 0 0 0 BMRU
lo 16436 0 1933675 0 0 0 1933675 0 0 0 LRU


Regards.

there's more to a network than just one interface.