[ntp:questions] Regarding updation of IP addresses in the ntpd.conf file

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Fri Jul 20 22:23:15 UTC 2012


Brian Utterback wrote:> BlackLists wrote:
>>   server 0.pool.ntp.org
>>   server 1.pool.ntp.org
>>   server 2.pool.ntp.org
>>   server 3.pool.ntp.org
>>
>> More recent versions of ntp, might replace all four
>>  of those lines with one line in the conf file, e.g.:
>>
>>   pool pool.ntp.org
>
> Not generally. For some reason each lookup of any of these
>  always returns 3 addresses. Since we still recommend four
>  servers (even if there is some dispute over the reasons),
>  using just pool.ntp.org won't work.
> Even is you do multiple lookups, if there is anything that
>  does any caching in between you and the DNS server that
>  sets the addresses, you will get the same three.
> I don't know why there are only three addresses.
>  The simplest solution would be for the round robin DNS
>   servers to give out more addresses, then you could just
>   have the single line.


I think you would have to have DNS servers that are breaking
 several of STD/RFC/ Best common Practices to really see that.

I see that to be not true.
When using the pool command (instead of server),
 ntp will keep pulling more IPs up to max clock (10 default),
 and then continue to pull more IPs
  whenever it finds a reason to discard a peer,
  and the quantity of peers drops below max clock.

I find that after running a long time,
 you end up with a nice click of servers,
 with the far away ones in other countries getting discarded.

 10 queries gets 18 unique IPs
 50 queries gets 33 unique IPs
100 queries gets 51 unique IPs

dns\bin>dig pool.ntp.org
; <<>> DiG 9.9.1-P1 <<>> pool.ntp.org
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 24882
;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;pool.ntp.org.          IN   A

;; ANSWER SECTION:
pool.ntp.org.      70   IN   A   108.59.14.130
pool.ntp.org.      70   IN   A   64.73.32.134
pool.ntp.org.      70   IN   A   67.18.187.111

;; Query time: 15 msec
;; SERVER: 206.13.29.12#53(206.13.29.12)
;; WHEN: Fri Jul 20 14:29:25 2012
;; MSG SIZE  rcvd: 89


dns\bin>dig +short pool.ntp.org
184.105.192.247
67.18.187.111
69.164.217.193

...



Feel free to try this on your own DNS servers,
 or just configure pool pool.ntp.org alone,
 and monitor the changing IPs your peerstats files.


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