[Nagiosplug-help] check_by_ssh passive?

[Arnold Cano]

Could someone please explain the following snip from the check_by_ssh
help?

"The most common mode of use is to refer to a local identity file with
the '-i' option. In this mode, the identity pair should have a null
passphrase and the public key should be listed in the authorized_keys
file of the remote host. Usually the key will be restricted to running
only one command on the remote server. If the remote SSH server tracks
invocation agruments, the one remote program may be an agent that can
execute additional commands as proxy
 
To use passive mode, provide multiple '-C' options, and provide
all of -O, -s, and -n options (servicelist order must match '-C'
options)"

Basically, what I don't understand is how to use check_by_ssh passively?
If possible, please provide a small example on how to use check_by_ssh
as a proxy as described.

Thanks,

Arnold