Redirect HTTP to HTTPS for some users

I like to use data groups in situations like this. You can make an address-type data group that contains the subnets you don't want to redirect. If you're using 10.x, your iRule will look something like this:

when HTTP_REQUEST { 
   if { [TCP::local_port] eq 80 and ![class match [IP::client_addr] eq datagroup] } {
     HTTP::redirect "https://[HTTP::host][HTTP::uri]" } }

That's how I'd do it anyways