For what you are doing, you will need to either edit scan.bro to
remove the hostnames, for example replacing
const skip_scan_sources = {
...
};
with
const skip_scan_sources: set[addr];
(you can't replace it with just "const skip_scan_sources = { };", because
then Bro can't figure out the variable's type); or you could arrange for
the DNS service on your box to resolve them directly via /etc/hosts.
Vern