[Pdns-users] multi dns server

[Andreas Danzer]

Hello Steffan,

that kind of attack is quite common these days. I would recommend 
putting your authoriative nameservers behind dnsdist. Dnsdist acts as a 
DNS firewall, proxy and loadbalancer.

We're running some rulesets on dnsdist, that e.g. dynamically block IPs 
that "produce" unusual high numbers of NXDOMAIN answers with their 
queries (which is usually the case with IPs taking part in PRSD 
attacks). You can also limit the number of queries per IP or loadbalance 
queries to more than one backend DNS node. dnsdist is extreme powerfull 
and versatile and the perfect tool to protect your DNS nodes.

To be able to see, which domains are actually attacked, you should not 
use pdns query logging - it has a big performance impact which makes the 
situation even worse during an attack. Better use some traffic 
capturing/sampling tools like pktvisor. It feeds data about the dns 
queries to prometheus, which can be visualized with grafana. You can use 
that same setup (prometheus & grafana) to monitor your dndist and pdns 
installations.

Am 20.10.2023 um 15:52 schrieb Steffan via Pdns-users:
> Well the problem was a small attack targeting a lot of subdomains of a client.
> 
> Oct 18 21:40:47 ns1 pdns_server[2135429]: Remote 117.54.16.252 wants 'payments.xxx.com|A', do = 1, bufsize = 1232 (4096): packetcache MISS
> Oct 18 21:40:47 ns1 pdns_server[2135429]: Remote 2a02:2f0e:5fff:ffff::2 wants 'skyline.xxx.com|A', do = 1, bufsize = 1232 (4096): packetcache MISS
> Oct 18 21:40:47 ns1 pdns_server[2135429]: Remote 2a04:c602:409:fe::27 wants 'app3.xxx.com|A', do = 1, bufsize = 1232: packetcache MISS
> 
> I comes from many different ips and only 3 minutes 150mb/s
> 
> I forgot on that time that I had logging on. So it could be that without the logging the dns would be fast enough to handle it
> 
> Average bandwith load is abouth 160k/s so no big deal.
> 
>   
> Met vriendelijke groet,
> 
> Steffan Noord
> 
> 
> 
> 
> 
> 
> -----Oorspronkelijk bericht-----
> Van: Victor Hugo dos Santos <listas.vhs at gmail.com>
> Verzonden: vrijdag 20 oktober 2023 15:45
> Aan: All about using and deploying powerdns <pdns-users at mailman.powerdns.com>
> CC: steffannoord at gmail.com
> Onderwerp: Re: [Pdns-users] multi dns server
> 
> Hello there,
> 
> The quantity of the domain, not necessarily reflect the quantity of queries/load.
> you can have 5.000 domains with 1.000 QPS or you can have 1 domain with  15.000 QPS !! :-)
> 
> Anyway, you should monitor your servers and see if this issue is some kind of "normal" stuff or some kind of problem (attack, data leak, misconfiguration, etc). When you detect the problem, then you can decide what to do.
> 
> About NS3, NS4, it is a totally valid option, not only to balance the queries between servers, but to improve your HA too !!! Nevertheless, you still need to detect where the problem is, if not, you are only going to spend time with the new NS server but the problem will still occur.
> 
> Let us know what you find.
> 
> Good luck
> 
> 
> 
> 
> 
> 
> 
> On Fri, 20 Oct 2023 at 12:01, Steffan via Pdns-users <pdns-users at mailman.powerdns.com> wrote:
>>
>> Hello,
>>
>>
>>
>> 2 days ago my 2 dns servers has 150mbit of data to process and the dns went down.
>> After the flood was stopped it came up again.
>>
>>
>>
>> Im using pdns 4.8.3 on centos with mysql backends
>>
>>
>> I just wondering what will the best idee to spread the risk
>>
>> It is handling about 5000 domains so not a very big system.
>>
>> is it better to use a ns3, ns4 to spread the loads on multi servers Or
>> some kind of load balancing or multi ip setup on ns1 and ns2 on multi
>> servers
>>
>>
>>
>> Any other idees are welcome
>>
>>
>>
>> With regard
>>
>>
>>
>> Steffan
>>
>>
>>
>>
>>
>>
>>
>>
>>
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> 
> 
> 
> --
> --
> Victor Hugo dos Santos
> http://www.vhsantos.net
> Linux Counter #224399
> 
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