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

[David Klatt]

Hi,

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:

    rrset-order {  order random;  };

and records like:

    foo  IN A  10.0.0.1
    foo  IN A  10.0.0.2
    foo  IN A  10.......N

Now I'd like bind to just return a  random subset  of e.g. 5 IP addresses
if someone requests this A record.

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.

For my use case I absolutely need to make sure that each IP of that large
A record set is given out equally (statistically) and that at any time when
bind answers that one A record it only returns a random subset of all these IPs.

Has someone an idea on how to achieve the latter?

Thanks a lot in advance!

David
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