F5 LTM - cipher logging

Are you trying to log all ciphers used during SSL connections?

Think you can use something like the SSL::cipher iRule command: iRules SSL::cipher

when HTTP_REQUEST {
    log local0. "[SSL::cipher name], [SSL::cipher version], [SSL::cipher bits]
}

Not sure if HTTP_REQUEST is the best event to use though as will log every request when you likely only want to log once per SSL session.