In Logstash versions prior to 5 myself and others use the free geoipasnum.dat from MaxMind considerably. The main reason we haven't switched to version 5 is it seems Logstash 5.0 requires the new geoip database format which does not offer a free ASN number database.
Is there a way to tell Logstash 5 to load the older GeoIP .dat format so we can continue using ASN # lookups?