What causes 'zone transfer setup failed' ?

[Jan-Piet Mens]

Hello,

I'm seeing quite a number of messages like

        xfer-out: debug 3: client 192.168.1.2#54688 (example.com): zone transfer setup failed

BIND 9.9.2P1 here, configured with:

        request-ixfr no;
        transfer-format many-answers;
        transfers-in 100;
        transfers-per-ns 100;
        max-transfer-time-in 60;

BIND has a lot of zones to transfer; does this have something to do with
too many TCP connections? 

FWIW, BIND is running on Centos 6.3 in an OpenVZ container.

Regards,

        -JP