Reference Guide

A constrained RBAC model provides for separation of duty and as a result, provides greater security than the hierarchical RBAC
model. Essentially, a constrained model puts some limitations around each role’s permissions to allow you to partition of tasks.
However, some inheritance is possible.
Default command permissions are based on CLI mode (such as configure, interface, router), any specific command settings, and
the permissions allowed by the privilege and role commands. The role command allows you to change permissions based on the
role. You can modify the permissions specific to that command and/or command option. For more information, see Modifying
Command Permissions for Roles .
NOTE: When you enter a user role, you have already been authenticated and authorized. You do not need to enter an
enable password because you will be automatically placed in EXEC Priv mode.
For greater security, the ability to view event, audit, and security system log is associated with user roles. For information about
these topics, see Audit and Security Logs.
Privilege-or-Role Mode versus Role-only Mode
By default, the system provides access to commands determined by the user’s role or by the user’s privilege level. The user’s
role takes precedence over a user’s privilege level. If the system is in “privilege or role” mode, then all existing user IDs can
continue to access the switch even if they do not have a user role defined. To change to more secure mode, use role-based AAA
authorization. When role-based only AAA authorization is configured, access to commands is determined only by the user’s role.
For more information, see Configuring Role-based Only AAA Authorization.
Configuring Role-based Only AAA Authorization
You can configure authorization so that access to commands is determined only by the user’s role. If the user has no user role,
access to the system is denied as the user will not be able to login successfully. When you enable role-based only AAA
authorization using the aaa authorization role-only command in Configuration mode, the Dell Networking OS checks to ensure
that you do not lock yourself out and that the user authentication is available for all terminal lines.
Pre-requisites
Before you enable role-based only AAA authorization:
1. Locally define a system administrator user role. This will give you access to login with full permissions even if network
connectivity to remote authentication servers is not available.
2. Configure login authentication on the console. This ensures that all users are properly identified through authentication no
matter the access point.
If you do not configure login the authentication on the console, the system displays an error when you attempt to enable
role-based only AAA authorization.
3. Specify an authentication method list (RADIUS, TACACS+, or Local).
You must specify at least local authentication. For consistency, the best practice is to define the same authentication
method list across all lines, in the same order of comparison; for example VTY and console port.
You could also use the default authentication method to apply to all the LINES (console port, VTY).
NOTE:
The authentication method list should be in the same order as the authorization method list. For example, if you
configure the authentication method list in the following order (TACACS+, local), Dell Networking recommends that
authorization method list is configured in the same order (TACACS+, local).
4. Specify authorization method list (RADIUS, TACACS+, or Local). You must at least specify local authorization.
For consistency, the best practice is to define the same authorization method list across all lines, in the same order of
comparison; for example VTY and console port.
You could also use the default authorization method list to apply to all the LINES (console port, VTY).
If you do not, the following error is displayed when you attempt to enable role-based only AAA authorization.
% Error: Exec authorization must be applied to more than one line to be useful, e.g.
console and vty lines. Could use default authorization method list as alternative.
5. Verify the configuration has been applied to the console or VTY line.
Dell (conf)#do show running-config line
!
line console 0
652
Security