Routing rules do give back 100% of the dropped events, but they are given back in the next 1 second interval. There is an article that describes the issue how it works here: https://www.ibm.com/support/pages/qradar-license-eps-rates-and-giveback
To drop the event, you need to use a custom property to identify the payloads that contain the values that you want to identify and drop.
The only other option would be to tune the remote Linux server to not generate as many events or you could add another Event Collect that is licensed as LOG ONLY, where those events do not count against the EPS license and go to a Data Store appliance. It might also be an option to have the Linux server write to a flat file as line-by-line events and scrub it using an external script. Using Routing Rules is much easier though.
The issue with license and routing rules is that routing happens after licensing in the QRadar Event Pipeline, so even though you are dropping events with a Routing Rule, the logs and system notification occur higher in the event pipeline as you are exceeding the licensed threshold and the notification triggers anyway.
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