The F5 removes gzip and deflate from the accept-encoding before sending the request on to the server. The default behavior of web servers is to only compress if the client have the accept-encoding gzip or deflate in its requests so the web server would not compress the content.
You can test it on the F5 with the following iRule:
when HTTP_RESPONSE {
log local0. [HTTP::header "Content-Encoding"]
}
The rule is triggered when the F5 receives the response from the pool member.
If the log entry is empty, ie ":" the Content-Encoding header is not present, which means that the server did not compress the content. If you still see the Content-Encoding: gzip in the answer in the web browser it means that the F5 compressed the material.
Hope this is good enough evidence.
Kind regards,
Patrik