Tips to speed up NTP synchronization

From: Huan Pham (Huan.Pham@peopletelecom.com.au)
Date: Mon Aug 25 2008 - 04:10:49 ART


Hi GS,

My NTP session takes normally 3 minutes to sync. On Dynamips sometimes
it takes 10 minutes or even forever to get synched.

Even 3 minutes is still too painfull to wait in a lab. I cannot stand
waiting in sane for the router that looks like doing nothing!

Any tips to get NTP synched faster? Or any verification (show/debug) to
make sure that the router is on the right track to getting clock
synchronized?

One of the tips I get from Brian Dennis in his CoD is to set clock
manually to so that routers clocks are not too apart. This does not
seems to help much. I still have it painfully 3 minutes long!

NTP on actuall routers takes 3 minutes to sync
----------------------------------------------

R1#sh run | in ntp
ntp master 1
R1#clock set 12:00:00 AUG 25 2008

R2#sh run | in ntp
ntp source Loopback0
ntp server 1.1.1.1

R2#debug ntp sync
NTP clock synchronization debugging is on
R2#debug ntp events
NTP events debugging is on

R2#clock set 12:00:00 AUG 25 2008

R2#
Aug 25 12:00:00.000: NTP: peer stratum change
Aug 25 12:00:00.000: NTP: sync lost
.Aug 25 12:00:00.000: %SYS-6-CLOCKUPDATE: System clock has been updated
from 12:06:56 UTC Mon Aug 25 2008 to 12:00:00 UTC Mon Aug 25 2008,
configured from console by console.

R2#
.Aug 25 12:02:48.845: NTP: synced to new peer 1.1.1.1
Aug 25 12:02:48.845: NTP: 1.1.1.1 synced to new peer
Aug 25 12:02:48.845: NTP: sync change
Aug 25 12:02:48.845: NTP: peer stratum change
Aug 25 12:02:48.849: NTP: 1.1.1.1 reachable
R2#
R2#sh ntp associations detail | in san
1.1.1.1 configured, our_master, sane, valid, stratum 1

NTP on Dynamips takes 10 minutes to sync
----------------------------------------

R1#sh run | in ntp|access-list
access-list 2 permit 2.2.2.2
ntp access-group serve 2
ntp master 1

R2#clock set 14:00:00 Aug 25 2008
R2#
Aug 25 14:00:00.000: NTP: peer stratum change
Aug 25 14:00:00.000: NTP: sync lost

R2#
.Aug 25 14:01:01.054: NTP: synced to new peer 1.1.1.1
.Aug 25 14:10:42.931: NTP: peer stratum change
.Aug 25 14:10:42.935: NTP: clock reset
R2#
.Aug 25 14:11:46.955: NTP: synced to new peer 1.1.1.1
Aug 25 14:11:46.955: NTP: 1.1.1.1 synced to new peer
Aug 25 14:11:46.959: NTP: sync change
Aug 25 14:11:46.959: NTP: peer stratum change
Aug 25 14:11:46.959: NTP: 1.1.1.1 reachable

NTP on Dynamips does not sync
-----------------------------

R1#sh run | in ntp|access-list
access-list 2 permit 2.2.2.2
ntp access-group serve 2
ntp master 1

R2#sh run | in ntp
ntp source Loopback0
ntp server 1.1.1.1

R2#clock set 14:00:00 Aug 25 2008
R2#
Aug 25 14:00:00.000: NTP: peer stratum change
Aug 25 14:00:00.000: NTP: sync lost

R2#sh clock
.14:29:53.256 UTC Mon Aug 25 2008
R2#sh ntp association detail
1.1.1.1 configured, insane, invalid, stratum 1
ref ID .LOCL., time CC5D3A8B.28F8AE75 (14:04:59.160 UTC Mon Aug 25 2008)
our mode client, peer mode server, our poll intvl 64, peer poll intvl 64
root delay 0.00 msec, root disp 0.03, reach 0, sync dist 7932.266
delay 92.19 msec, offset 9.4140 msec, dispersion 16000.00
precision 2**24, version 3
org time CC5D4031.831262C4 (14:29:05.511 UTC Mon Aug 25 2008)
rcv time CC5D402E.1ED77782 (14:29:02.120 UTC Mon Aug 25 2008)
xmt time CC5D402E.0A515629 (14:29:02.040 UTC Mon Aug 25 2008)
filtdelay = 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00
filtoffset = 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00
filterror = 16000.0 16000.0 16000.0 16000.0 16000.0 16000.0 16000.0
16000.0

R2#sh ntp status
Clock is unsynchronized, stratum 16, no reference clock
nominal freq is 250.0000 Hz, actual freq is 250.0000 Hz, precision is
2**24
reference time is CC5D3C62.F5F303BE (14:12:50.960 UTC Mon Aug 25 2008)
clock offset is 9.4140 msec, root delay is 92.19 msec
root dispersion is 7889.71 msec, peer dispersion is 7880.28 msec

Blogs and organic groups at http://www.ccie.net



This archive was generated by hypermail 2.1.4 : Mon Sep 01 2008 - 08:15:32 ART