https://docs.splunk.com/Documentation/Splunk/8.0.4/Data/Whitelistorblacklistspecificincomingdata
"It is not necessary to define both an allow list and a deny list in a configuration stanza. The settings are independent. If you do define both filters and a file matches them both, Splunk Enterprise does not index that file, as the blacklist filter overrides the whitelist filter." Source: https://docs.splunk.com/Documentation/Splunk/8.1.0/Data/Whitelistorblacklistspecificincomingdata

https://docs.splunk.com/Documentation/Splunk/7.0.3/Forwarding/Routeandfilterdatad#Perform_selective_indexing_and_forwarding Specifies a comma-separated list of tcpout group names. Use this setting to selectively forward your data to specific indexers by specifying the tcpout groups that the forwarder should use when forwarding the data. Define the tcpout group names in the outputs.conf file in [tcpout:<tcpout_group_name>] stanzas. The groups present in defaultGroup in [tcpout] stanza in the outputs.conf file.

https://docs.splunk.com/Documentation/Splunk/8.2.1/Updating/Filterclients Reference:
same/td-p/390910