Using TACACS+ Authentication

You can use a TACACS+ server to authenticate users. When TACACS+ authentication is enabled, the Cisco Provider Connectivity Assurance Sensor Control supports Authentication and Authorization as configured on the TACACS+ server. A TACACS+ server can be useful if you want to centrally manage user accounts instead of managing them separately on each Sensor Control. A Sensor Control can be configured to connect to a second TACACS+ server, allowing for TACACS+ server redundancy.

Configuring TACACS+ Session Parameters

▶ To configure TACACS+ session parameters

1. Access the page System ▶ Session ▶ TACACS+.

   The TACACS+ Configuration form displays.

2. Complete the required fields, then click Apply.

   For information, see TACACS+ Configuration Parameters.

TACACS+ Configuration Parameters

This section describes the TACACS+ Configuration form parameters.

General

Server-1 / Server-2

TACACS+ Server Configuration Examples

The following examples are configurations for the TACACS+ server, not for the Sensor Control. They can be applied to a tac_plus server; configuration values may differ for other servers.

Logging in is a two-part process. First, the user is authenticated. Once authenticated, the user may be authorized to gain rights on the system. The server should return AV (attribute-value) pairs for the requested service name.

The first attribute, the privilege level (usually priv-lvl), is evaluated first. This attribute is a numerical value that should be between 0 and 15. On this system, an attribute value of 15 grants Admin rights (All-show, All-Add, All-edit), and all other attribute values grant Viewer rights (All-show). If the specified attribute value is not found, the login attempt is refused because the AV pair was not supplied by the server.

The second attribute, the privilege list (accedian-priv-list), is subsequently evaluated. This attribute is an optional attribute, and is ignored if the privilege level is already set to 15 (Admin). The purpose of this attribute is to provide a fine-grained permissions mechanism. The permissions are the same as those that can be configured locally on the Sensor Control. The list of tokens is separated by commas. The case-sensitive tokens you indicate can be a mix of locally-defined user permission groups and individual privileges.

Following are configuration examples for the TACACS+ Server using these attributes.

▶ To assign a user to the built-in Admin group

user = tacadmin {
login = cleartext tacadmin
pap = cleartext tacadmin
name = "Test Admin"
# 'shell' service referred to as 'exec'
# in the config
service = exec {
priv-lvl = 15
}
}

▶ To assign a user viewer-only privileges

user = tacviewer {
login = cleartext tacviewer
pap = cleartext tacviewer
name = "Test Tac Viewer"
# 'shell' service referred to as 'exec'
# in the config
service = exec {
priv-lvl = 1
}
}

▶ To assign a user a customized set of privileges

user = taccfm {
login = cleartext taccfm
pap = cleartext taccfm
name = "Test Tac User CFM"
# 'shell' service referred to as 'exec'
# in the config
service = exec {
priv-lvl = 1
accedian-priv-list = CFM,PAA
}
}

If a user is authenticated by TACACS+, but no attributes are specified in the server configuration, the permissions will be set as follows:

• If the username exists locally: Local permissions, as configured on the Sensor Control
• If the username does not exist locally: Viewer-only permissions