This read-write object sets the authentication mode used when switches join the stack: none, a simple password, or MD5-based authentication. Choosing simple(1) or md5(2) requires a matching tpStackAuthKey to be configured, since that key is what new members must present to be accepted into the stack. For example, an admin securing stack membership against unauthorized devices would set tpStackAuthMode to md5(2) and configure a shared key on every member switch.