I have two devices where one keeps itself synchronized to within 5-10 usec of the NTP servers but the other one varies _wildly_, sometimes having an offset of ~150 ms. The NTP servers are two CentOS 5.4 servers, themselves using two Meinberg M300 GPS devices as stratum 1 sources.
Working device: C2801 running 12.4(24)T3 Enterprise Base, 128 MB RAM. Connected to a 3560E as an access device, Fa0/0 has an IP address and a default route pointing at the gateway for that access VLAN. NTP update source is this interface. Non-working device: C2801 running 15.0(1)M2 Enterprise Service, 256 MB RAM. Connected redundantly to two 6500/Sup720s on L3 interfaces. Running IS-IS and MPLS. NTP update source is a Loopback interface. None of the devices are CPU or traffic loaded in any serious way (30% peaks about once per hour, otherwise <3%). Both devices are supposed to be doing IP SLA collection. NTP configuration is the same, with just the two servers configured and an update source for one device. (I've cleared the auth config to see if that was it, no change.) The non-working device: non_working#sh ntp status Clock is synchronized, stratum 3, reference is 10.85.247.20 nominal freq is 250.0000 Hz, actual freq is 250.0181 Hz, precision is 2**24 reference time is CFD496F6.08BA94AC (17:59:50.034 CEST Tue Jun 29 2010) clock offset is -27.2854 msec, root delay is 3.51 msec root dispersion is 50.75 msec, peer dispersion is 1.26 msec loopfilter state is 'CTRL' (Normal Controlled Loop), drift is -0.000072382 s/s system poll interval is 16, last update was 70 sec ago. non_working#sh ntp ass address ref clock st when poll reach delay offset disp *~10.85.247.20 10.83.8.130 2 8 16 377 1.778 -27.285 1.116 +~10.83.247.20 10.83.8.130 2 0 16 377 0.877 -26.844 1.302 * sys.peer, # selected, + candidate, - outlyer, x falseticker, ~ configured non_working# And the working device: working#sh ntp status Clock is synchronized, stratum 3, reference is 10.83.247.20 nominal freq is 250.0000 Hz, actual freq is 250.0274 Hz, precision is 2**24 reference time is CFD49516.7C7CB895 (17:51:50.486 CEST Tue Jun 29 2010) clock offset is -0.0051 msec, root delay is 0.00 msec root dispersion is 0.04 msec, peer dispersion is 0.00 msec loopfilter state is 'CTRL' (Normal Controlled Loop), drift is -0.000109809 s/s system poll interval is 256, last update was 564 sec ago. working#sh ntp ass address ref clock st when poll reach delay offset disp +~10.85.247.20 10.83.8.130 2 233 256 377 1.759 -5.567 8.367 *~10.83.247.20 10.83.8.130 2 232 256 377 0.877 -5.194 7.547 * sys.peer, # selected, + candidate, - outlyer, x falseticker, ~ configured working# I tried many things, among others to fix the maxpoll interval, adjust scheduler allocation, disable authentication, reset the configuration completely (with "no ntp <cr>") and reset the clock to when Prince was still young to force a "stepping". Still the 15.0(1)M2 Ent Serv. simply cannot keeps a precise time. Reachability is perfect (377 all the time) and the device can even see the root offset! It just cannot adjust correctly. I know it takes time (why can't I have an explicit "step" command in IOS?) but the offset varies, also getting worse over time. Is it because of the extra MPLS encapsulation? The newer IOS version? Another feature set? Or should I just give up? :-) -- Peter _______________________________________________ cisco-nsp mailing list cisco-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
