[ntp:questions] Re: two ntp servers

rancid moth rancidmoth at yahoo.com
Mon Feb 20 21:44:26 UTC 2006


hello john

no it seems to definitely be reaching them.  i have checked using the 
dmpeers command.  also running the ntpq -p i get the exact same thing as 
what is on the other box.  also note that in my trials i have set a machines 
time from off the other machine and made them perfectly in synch.  when i 
then take that machine and point it to the upstream server it then drifts 
until it is three minutes ahead.  i just dont get it.  odd dont you think?







"John Pettitt" <jpp at cloudview.com> wrote in message 
news:43F4FDCA.3070402 at cloudview.com...
> rancid moth wrote:
>> hello,
>>
>> not being very familiar with the ntp protocol, and currently introducing
>> myself to it properly (i.e. have always used though never dug deeply into
>> it), i have established two ntp services on two different Linux machines.
>> Both ntp servers are pointing to the _same_ upstream server.  There is a
>> four minute difference in time on the machines.  Lets call them machine A
>> and B.  initially i established them to the same time, by synching B's 
>> time
>> from A which itself was synched from the upstream internet ntp server. 
>> If i
>> then modify B's config to also synch from the same upstream source, B, 
>> given
>> enough time, will drift 4 minutes ahead of A.  Can someone please point 
>> me
>> to an introductory explanation as to why/how this can occur.
>>
>> cheers
>> moth
>>
>>
>
> Basically your setup isn't working for some reason - if you do "ntpq -p" 
> on both boxes you'll
> probably see that one or both of them are not actually talking to the 
> upstream.    As a general rule
> you need at least four upstream servers for stability (see 
> www.pool.ntp.org for how to get more
> servers).  It's probably a good idea to peer the two local servers and 
> then point them at diverse
> (overlapping is ok) groups of upstream servers as this will give to a very 
> robust setup.
>
> If I had to guess I'd say that a firewall somplace is blocking the ntp 
> packets.
>
> John 





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