NTP won't sync 2

[plshlpme]

I have 3 2650XM routers that i cannot get to sync to a NTP server.

cisco of course wanted me to upgrade the IOS. and then said that it was due to the inconsistency in delay on the circuit.
i had my customer turn their router into a ntp master and i was still not able to sync over the lan.

other then a hardware problem does anybody have any ideas of what else the problem may be?

ios is c2600-is-mz.123-10d
and all three routers are configured exactly teh same as my other 65 routers that sync no problem.

the 3 routers have this for the ntp config

ntp source Loopback0
ntp server y.y.y.y
ntp server x.x.x.x

ntp server y.y.y.y:
ntp source Loopback0
ntp master 3
ntp peer x.x.x.x

ntp server x.x.x.x:
ntp source Loopback0
ntp master 3
ntp peer y.y.y.y

this has been bugging me for a while and im at the point where i think im going to change out the routers for new ones unless anybody has come across this before?

thanks

 

[itguynyc]

I've had a similar problem and after 4 months of troubleshooting with Cisco I git their tech to leak out some information that was very useful. There were a batch of routers with a processor revision of 0x300 shipped globally that have problems synching up. Please verify that your router's processor does not have this revision by running a show version command. Hope this helps!

 

[plshlpme]

cisco 2621XM (MPC860P) processor (revision 0x301)
cisco 2650XM (MPC860P) processor (revision 0x200)

none of the faulty ones have that revision...
only common thing between them all is every router in the network has a part number 73-7755-xx
while the two that dont work are 73-7677-xx

coincidence?

one of the routers is being swapped next week.
we will see

 

[plshlpme]

well....
router swapped... clock now syncs. fancy that
Part Number : 73-7756-XX

so it appears that part# 73-7677-XX have a bug with regards to ntp..
just put the order in to replace the other router now
thanks for all the replies everybody.