Peter,
I'm not a NTP expert but I know there were some issues when it went to
v4 regarding sync times, etc...
One of them was:
CSCte91471 NTP v4 takes several hours to sync when multiple servers
are configured
From looking at the source code that fix doesn't appear to be in 15.0(1)M2.
You may want to try it with the next rebuild when it comes out.
Rodney
On 6/29/10 6:13 PM, Peter Rathlev wrote:
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? :-)
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