If a box has been hardened it may be very reluctant to use the old rsh/rexec/rcmd/rlogin style remote command execution.

The old model basically says than a group of machines are equivalent securitywise, also the protocols may pass the passwords in clear.

Today, you will get better mileage with the ssh protocols. The only reason I would use the old rsh etc protocols is if talking to a legacy machine and I can't find an alternative.