I have a 6509 which just wont ntp sync no matter which synced up device I point it too, I think it's something to do with a server that should be getting it's ntp update from my switch which you can see in paste below. This switch is connected to a router which is synced up with another router which in turn is synced up to a ntp server, it doesn't matter which device I point my switch at, the stratum is always 16 and it's not blocked by an acl.
config of ntp switch
ntp clock-period 17180032
ntp source Loopback0
ntp server 10.231.223.130 prefer
ntp server 10.181.206.209
sh ntp status
Clock is unsynchronized, stratum 16, no reference clock
nominal freq is 250.0000 Hz, actual freq is 249.9976 Hz, precision is 2**18
reference time is CED80B6F.E15D73F7 (02:33:19.880 GMT Sun Dec 20 2009)
clock offset is 2.6046 msec, root delay is 59.16 msec
root dispersion is 4.65 msec, peer dispersion is 0.81 msec
sh ntp associations
address ref clock st when poll reach delay offset disp
10.231.65.6 .LOCL. 1 13 64 101 0.0 0.00 16000.
~10.231.223.130 0.0.0.0 16 - 64 0 0.0 0.00 16000.
~10.181.206.209 0.0.0.0 16 - 64 0 0.0 0.00 16000.
* master (synced), # master (unsynced), + selected, - candidate, ~ configured
If you see the ntp associaion output it says
The 'reach' counter shows a value of 0 for the following configured NTP
server IP address(es):
This means that the device did not receive at least the last eight NTP packets it expects to receive. Usually this counter shows a value of "377" which means that device has received at least the last eight NTP packets.
Try the following steps
Make sure that NTP server IP address(es) mentioned above is reachable by pinging
the server IP address(es).
Enable the debug ntp packet command to make sure that NTP packets are received
Issue the command show ntp status on the server(s) to make sure that NTP server
has synched itself. If it is not synched, verify the server NTP configuration.
The show ntp status of the server should display a status of 'sync' before
clients can sync their clock with the server. If the NTP server is not synchronized
itself try to disable and re-enable the NTP configuration on the server.
Verify that the 'stratum' value configured on the server is valid for your setup.
Configure a high stratum number to ensure that this router does not override
the clock on another system with a lower stratum number. The lower stratum number
indicates a more reliable clock.
After these steps if no use just delete the ntp configuration and then configure once then check what is the status.
Hope that helps out your query !!