In my design, there are collectors placed in security zones, receiving logs from a great number of Linux servers and forwarding the incoming to a Master Collector. This works perfectly fine :) My Collector's Input is defined like:

<Extension _syslog>
    Module    xm_syslog
</Extension>
<Input in1>
    Module    im_tcp
    Host    0.0.0.0
    Port    514
    Exec    parse_syslog();
</Input>

but with one exception: In one of the zones I'm supposed to receive logs from the firewall - I can see in the nxlog.log the connection is accepted, but then it says

connection accepted from [X.X.X:X]:port
couldn't bind tcp socket to [X.X.X.X]:514; cannot assign requested address

and I don't get any firewall logs.

What is the proper fix for this?