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New Member

Not sync with NTP Server(Cisco 1812J)


My customer have used  Cisco 1812J and It have configured as a NTP server.

I tried to connect Linux-PC(NTP Client) with Cisco 1812J, but it's never synchronize.

("ntpq -p" on Linux-PC)

     remote           refid      st t  when poll reach   delay   offset  jitter
==============================================================================      2 u   59   64    1    0.512    0.044    0.001

IP (Cisco 1218J)

IP (Linux-PC)

I monitored each packet using tcpdump, and I found "precision" was "e0" (-32) on reply data from Cisco 1812J.

I think -32 is too little. (Usually, -9 to -20 are specified)

Is -32 an appropriate value ?

14:03:20.221644 IP > NTPv3, Client, length 48
    0x0000:  4510 004c 0019 4000 4011 b421 c0a8 0215  E..L..@.@..!....
    0x0010:  c0a8 02f1 007b 007b 0038 2c71 db00 04ec  .....{.{.8,q....
    0x0020:  0000 0000 0000 0195 494e 4954 0000 0000  ........INIT....
    0x0030:  0000 0000 cfbc 4206 3969 c1a6 cfbc 4206  ......B.9i....B.
    0x0040:  34f7 65fd cfbc 4218 38bb d380            4.e...B.8...
14:03:20.222125 IP > NTPv3, Server, length 48
    0x0000:  45c0 004c 0000 0000 ff11 348a c0a8 02f1  E..L......4.....
    0x0010:  c0a8 0215 007b 007b 0038 d087
1c02 04e0 .....{.{.8......
    0x0020:  0000 002d 0000 07e5 0a0d 09f1 cfbc 41f1  ...-..........A.
    0x0030:  4458 a7fc cfbc 4218 38bb d380 cfbc 4218  DX....B.8.....B.
    0x0040:  3d62 8d9c cfbc 4218 3d63 2297            =b....B.=c".

Does anybody know the modification method of this "precision" data ?

Please tell me.


Cisco 1812J

IOS version : Ios 124-11.XW10

Hall of Fame Super Silver

Re: Not sync with NTP Server(Cisco 1812J)


One possible problem when NTP does not sync is that the client does not have good IP connectivity to the server. But from the output that you posted it looks to me like the client and server are communicating satisfactorily (and since they appear to be in a connected subnet connectivity should not be a problem).

Another possible issue occurs when the configured server (your 1812J) is not learning correct/authoritative NTP time. Could you post the output of show ntp status from the 1812J?



New Member

Re: Not sync with NTP Server(Cisco 1812J)

Richard, Thank you for your reply.

OK, I will post the NTP status of 1812J, if I can get it. ( 1812J is different in a person in charge. )

By the way, you said "server is not learning correct/authoritative NTP time", Is not "leap indicator" used in such a case ?

(I forgot to comment, ntpdate execute before running the ntpd and it's successfully complete.)

Is not the cause found only by the data of sending and receiving?

Is the method of easily knowing the reason why NTP doesn't synchronize?