How to get random subset of large rrset (30+ IPs for round robin)?

Matus UHLAR - fantomas uhlar at
Sat Mar 21 16:00:46 UTC 2020

>> >On Fri, Mar 20, 2020 at 3:14 AM David Klatt <d.klatt at> wrote:
>> >> I can't find a way to do the following although I invested plenty of time
>> >> in research - maybe you guys have an idea:
>> >>
>> >> With bind, I'd need to serve a single A record with  30+  IP addresses  and
>> >> these addresses have to be returned in random order round robin,
>> >> which is done with:
>> >> Now I'd like bind to just return a  random subset  of e.g. 5 IP addresses
>> >> if someone requests this A record.
>> On 20.03.20 10:37, Warren Kumari wrote:
>> >I realize that this is the BIND list, but this sounds like an almost
>> >perfect example of PowerDNS's LUA record type (or something with
>> >CoreDNS)
>> >Other than that, the only thing I can think of is BIND with DLZ and a
>> >database that returns a random subset from a DB query, but that sounds
>> >awful...

>On Fri, Mar 20, 2020 at 1:04 PM Matus UHLAR - fantomas <uhlar at>
>> I don't think BIND can do this at all. And I don't think it should...
>> >> Reason for this are in my case some (thousands) older clients (that I can't control)
>> >> that seem not being able to handle that many IPs - the OS resolver just returns an error.
>> why no use IPVS-like load balancer and hide all hosts behind one or two IPs?
>> that would help you much more, amongst others when any of those machines
>> fails.

On 20.03.20 13:15, Warren Kumari wrote:
>That's almost definitely the right answer, but there *are* cases where
>something like what the OP was asking for - springs to
>mind as one example.
>But, yes, a load balancer / anycast is almost definitely going to be a
>better choice...

according to the OP request mentioning multiple 10.0.0.* addresses I assumes
this is not the case of IPs spread over the world but more like a server farm
providing the same services.

In that case IPVS would help.

I realize not I shouldn't have removed the IPs from my reply so it would be
more clear.
Matus UHLAR - fantomas, uhlar at ;
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