IPCM - Configure User Profile - Realm Specification
The Realm field on the Users page specifies a password authority IPCM presents to the browser when requesting user authentication, and encodes passwords. This means:
• The administrators of two servers who do not want to share users and passwords must use different realms; otherwise, it is impossible to input a different password for the same user name when accessing another server, as the browser will recognize the realm and send the cached credentials instead of prompting the user for current credentials.
• Changing the realm resets all user passwords to the default value of password. As a result, the realm can only be modified with the password of the current administrator. Changing the realm also clears all phone passwords, effectively making all phones trusted (refer to Security Tab).