External Monitor for Pool

How?

By writing a script. Of some sort. The language is up to you. As long as it's available on the BigIP Host. Generally that means stuff like bash, or perl. Although in theory you could write a full app in C, compile it and upload (It's an x86 RH Linux Host after all). If you do, I'd recommend statically binding it though.

There's a spec in the manuals for the returns the external monitor is expected to make to tell BigIP whether the service is up or down too.

There's also an example monitor in there. On the host you should find it at /config/monitors/sample_monitor and it's written in bash.

How complex is of course up to you or your clients. Once your small app is written (Which could be as simple as altering the sample) you upload it via the GUI (Or tmsh, or iControl) and assign it to your pool...

Now... Will a built-in work? I'm sorry to say I have no idea about the CES mirror service... if it's a web front end and there's a simple URL to hit to determine availability, then yeah. Should do. Worst case, you could use a simple tcp monitor... I've seen it done, and sometimes it's all you need.

H