[c-nsp] NTP Sync Problem

[Jee Kay]

I have a new 2611XM that's just been installed, which is absolutely
refusing to synchronise to our NTP clock sources.

The really bizarre thing is that it appears to be correctly picking up
its offset and showing how far it is deviating in 'sh ntp ass', but it
won't actually slave itself to a source.

A debug ntp <various> produces the following:

.May  7 12:48:53.711 BST: NTP: xmit packet to ntp-server-1:
.May  7 12:48:53.711 BST:  leap 3, mode 3, version 3, stratum 0, ppoll 64
.May  7 12:48:53.711 BST:  rtdel 107C (64.392), rtdsp 1D5CDC
(29362.732), refid xxxxxx (ntp-server-1)
.May  7 12:48:53.711 BST:  ref C8085B32.295C96EA (12:40:34.161 BST Sun
May 7 2006)
.May  7 12:48:53.711 BST:  org C8085C8E.9BDC9E04 (12:46:22.608 BST Sun
May 7 2006)
.May  7 12:48:53.715 BST:  rec C8085CE5.B7660509 (12:47:49.716 BST Sun
May 7 2006)
.May  7 12:48:53.715 BST:  xmt C8085D25.B61DBC93 (12:48:53.711 BST Sun
May 7 2006)
.May  7 12:48:53.715 BST: NTP: rcv packet from ntp-server-1 to
ntp-client on FastEthernet0/0:
.May  7 12:48:53.715 BST:  leap 0, mode 4, version 3, stratum 4, ppoll 64
.May  7 12:48:53.715 BST:  rtdel 0E09 (54.825), rtdsp 7EB19
(7918.350), refid 9A0FFC82 (154.15.252.130)
.May  7 12:48:53.715 BST:  ref C8085C99.DC851122 (12:46:33.861 BST Sun
May 7 2006)
.May  7 12:48:53.719 BST:  org C8085D25.B61DBC93 (12:48:53.711 BST Sun
May 7 2006)
.May  7 12:48:53.719 BST:  rec C8085CC2.2A70D0CC (12:47:14.165 BST Sun
May 7 2006)
.May  7 12:48:53.719 BST:  xmt C8085CC2.2A75FB2C (12:47:14.165 BST Sun
May 7 2006)
.May  7 12:48:53.719 BST:  inp C8085D25.B7A047D5 (12:48:53.717 BST Sun
May 7 2006)
.May  7 12:48:53.719 BST: NTP: nlist 0, allow 0, found 0, low
0.000000, high 0.000000
.May  7 12:48:53.719 BST: NTP: no select intersection
.May  7 12:48:53.719 BST: NTP: no select intersection


As far as I can tell, the problem is the last two lines - it has
decided none of the sources are worthy of being a master clock. The
strange thing is I have lots of other equipment (including exactly the
same model/IOS of Cisco) syncing to these masters already with no
problem.

Does anyone know what's going on here? The IOS on the problem router
is 12.3(18).

Thanks,
Ras