How can I achieve the above? I've read about the LB::down command, but that doesn't necessarily delete all the connections, it just "downs" the member. Is there another command available that I can use?
You can't delete connection table entries from an iRule in the scenario you describe. You can reject connections, but that can only be done in an event. It would be very inefficient or impossible to try to do this for all existing connections to a specific pool member.
You could potentially do this with an iControl application, but I'm not sure how you would trigger the application. Perhaps you could post in the iControl section to get some ideas (Click here).