Hi everyone, I'm the one responsible for this discussion (I sent a question directly to Ask about it.)
To put some concrete numbers out there, I added 3 ntp servers to the pool (with v4 and v6 addresses) and see an increase of about 2 Million DNS queries per month per server. That's AFTER I defined PTR records for the servers with TTL 86400; before that, I was seeing about 9 Million queries per month per server (with negative caching at 3 minutes TTL.) Even 9 million queries per month per server isn't outrageous, but it's a big enough jump for our small company (we previously had about 1.5 million queries per month, overall) that I had to track it down and find the cause (it also caused a small overage fee with our DNS hosting provider.) At 2 million it's fine; I just thought it would be a good idea to add a note to the joining instructions recommending that admins create PTR records with long TTLs for any new servers being added to the pool. Adam ________________________________________ From: pool [[email protected]] On Behalf Of Ask Bjørn Hansen [[email protected]] Sent: Saturday, June 06, 2015 18:06 To: Hal Murray Cc: [email protected]; Hal Murray Subject: Re: [Pool] PTR queries? My best (eh, only...) guess is that some firewall software does the PTR queries. I can't think of a scenario where an NTP client would bother. I am surprised this is so (relatively) common though. I will add a note on the join.html page about it. Ask — http://askask.com/ On Fri, Jun 5, 2015 at 3:58 PM, Hal Murray <[email protected]> wrote: > [email protected] said: >> that's more or less normal, since ntpd (and maybe other software) >> is resolving the currently used IP address to a host name. > Which part of ntpd does a reverse lookup? > ntpd does a forward lookup if you use names in your server line in the config > file. > ntpq -p does a reverse lookup > -- > These are my opinions. I hate spam. > _______________________________________________ > pool mailing list > [email protected] > http://lists.ntp.org/listinfo/pool _______________________________________________ pool mailing list [email protected] http://lists.ntp.org/listinfo/pool _______________________________________________ pool mailing list [email protected] http://lists.ntp.org/listinfo/pool
