FW: SV: Bind bind high recv-q

[Mohammed Shareef]

Hi All,

I have 140 windows dns server on which we have install ISC bind services, I would like to know any script to flush the dns in all cache.

Thanks & Regards,

Mohammed Shareef


> From: SOAN at stofa.dk
> To: dot at dotat.at
> Subject: SV: Bind bind high recv-q
> Date: Sun, 6 Dec 2015 19:58:38 +0000
> CC: bind-users at lists.isc.org
> 
> Hi Tony,
> 
> Nope, my server is not an open resolver, but a lot of clients are using it :) - Actually one of my customers had a broken netgear device that was making 1000 qps for  time-g.netgear.com. Probably some kind of software bug.
> 
> I can recommend dnstop to find "bad dns clients" - But dnstop also showed me I'm getting 5-7K qps, and not 700-800 as collectd showed me. 
> 
> Do you think this is too much for a VM? - My VM is only loaded 50% on each core.
> 
>  /Søren
> 
> -----Oprindelig meddelelse-----
> Fra: Tony Finch [mailto:fanf2 at hermes.cam.ac.uk] På vegne af Tony Finch
> Sendt: 4. december 2015 13:34
> Til: Søren Andersen <SOAN at stofa.dk>
> Cc: bind-users at lists.isc.org
> Emne: Re: Bind bind high recv-q
> 
> Søren Andersen <SOAN at stofa.dk> wrote:
> >
> > I'm experiencing some strange problems with my bind installation. - I 
> > notice my bind recv-q is quite high sometimes.. therefore my DNS 
> > clients can experience DNS lookup to take 1-4 secs. My bind is running 
> > on a 4 core vm I VMware with 8Gb ram. - At peak I receive app. 700-800 
> > QPS. - The load is 20-40% on each CPU core. - I've also configured 2 RPZ zones.
> 
> Is your server an open resolver being used as part of a DDoS attack?
> 
> Do you have compromised client machines running malware that hammers your server?
> 
> Find out where the queries are coming from using netflow or tcpdump or query logging.
> 
> Tony.
> --
> f.anthony.n.finch  <dot at dotat.at>  http://dotat.at/ Southeast Iceland: Southeasterly 6 to gale 8, becoming cyclonic 7 to severe gale 9, then veering westerly gale 8 to storm 10, perhaps violent storm 11 later. High or very high later. Wintry showers. Moderate or poor, occasionally very poor.
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