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Contents
- Configuring AAA
- Information about AAA
- AAA Security Services
- Authentication
- Authorization
- Accounting
- AAA Server Groups
- Prerequisites for AAA
- Guidelines and Limitations
- AAA Default Settings
- Configuring AAA
- Configuring a Login Authentication Method
- Enabling Login Authentication Failure Messages
- Verifying the AAA Configuration
- Configuration Examples for AAA
- Feature History for AAA
Configuring AAA
This chapter contains the following sections:
- Information about AAA
- Prerequisites for AAA
- Guidelines and Limitations
- AAA Default Settings
- Configuring AAA
- Verifying the AAA Configuration
- Configuration Examples for AAA
- Feature History for AAA
Information about AAA
AAA Security Services
Based on a user ID and password combination, authentication, authorization, and accounting (AAA) is used to authenticate and authorize users. A key secures communication with AAA servers.
In many circumstances, AAA uses protocols such as RADIUS or TACACS+ to administer its security functions. If your router or access server is acting as a network access server, AAA is the means through which you establish communication between your network access server and your RADIUS or TACACS+ security server.
Although AAA is the primary (and recommended) method for access control, additional features for simple access control are available outside the scope of AAA, such as local username authentication, line password authentication, and enable password authentication. However, these features do not provide the same degree of access control that is possible by using AAA.
Separate AAA configurations are made for the following services:
- User Telnet or Secure Shell (SSH) login authentication
- Console login authentication
- User management session accounting
The following table provides the authentication commands:
Authentication
Authentication provides the method of identifying users, including login and password dialog, challenge and response, messaging support, and, depending on the security protocol that you select, encryption. Authentication is the way a user is identified prior to being allowed access to the network and network services. You configure AAA authentication by defining a named list of authentication methods and then applying that list to various interfaces.
Authentication is accomplished as follows:
Authentication Method
Description
Local database
Authenticates the following with a local lookup database of usernames or passwords:
Remote RADIUS or TACACS+ server
Authenticates the following with a local lookup database of usernames or passwords:
None
Authenticates the following with only a username:
The following figure shows a flowchart of the authentication process.
Authorization
Authorization restricts the actions that a user is allowed to perform. It provides the method for remote access control, including one-time authorization or authorization for each service, per-user account list and profile, user group support, and support of IP, IPX, ARA, and Telnet.
Remote security servers, such as RADIUS and TACACS+, authorize users for specific rights by associating attribute-value (AV) pairs, which define those rights, with the appropriate user. AAA authorization works by assembling a set of attributes that describe what the user is authorized to perform. These attributes are compared with the information contained in a database for a given user, and the result is returned to AAA to determine the user’s actual capabilities and restrictions.
Accounting
Accounting provides the method for collecting and sending security server information used for billing, auditing, and reporting, such as user identities, start and stop times, executed commands (such as PPP), number of packets, and number of bytes. Accounting enables you to track the services that users are accessing, as well as the amount of network resources that they are consuming.
Accounting tracks and maintains a log of every SVS management session. You can use this information to generate reports for troubleshooting and auditing purposes. You can store accounting logs locally or send them to remote AAA servers.
AAA Server Groups
Remote AAA server groups can provide failovers if one remote AAA server fails to respond, which means that if the first server in the group fails, the next server in the group is tried until a server responds. Multiple server groups can provide failovers for each other in this same way.
If all remote server groups fail, the local database is used for authentication.
Guidelines and Limitations
The Cisco Nexus 1000V does not support usernames that have all numeric characters and does not create local usernames that have all numeric characters. If a username that has all numeric characters already exists on an AAA server and is entered during login, the Cisco Nexus 1000V does not authenticate the user.
Configuring AAA
Configuring a Login Authentication Method
Before You BeginProcedureLog in to the CLI in EXEC mode.
If authenticate with TACACS+ server groups, you must have already added the groups.
The following example shows how to configure a local authentication method:
switch# configure terminal switch(config)# aaa authentication login console group tacgroup switch(config)# exit switch# show aaa authentication default: group tacgroup console: group tacgroup switch# copy running-config startup-config switch#switch# configure terminal switch(config)# aaa authentication login default group tacacs switch(config)# aaa authentication login console group tacacsEnabling Login Authentication Failure Messages
ProcedureYou can enable the login authentication failure message to display if the remote AAA servers do not respond.
The following is the login authentication failure message:
Remote AAA servers unreachable; local authentication done. Remote AAA servers unreachable; local authentication failed.
Command or Action Purpose
Step 1 switch# configure terminal Enters global configuration mode.
Step 2 switch(config)# aaa authentication login error-enable Enables the login authentication failure message. The default is disabled.
Step 3 switch(config)# exit Exits global configuration mode and returns you to EXEC mode.
Step 4 switch# show aaa authentication login error-enable (Optional) Displays the login failure message configuration.
Step 5 switch# copy running-config startup-config (Optional) Copies the running configuration to the startup configuration.
Verifying the AAA Configuration
Use one of the following commands to verify the configuration:
Command
Purpose
show aaa authentication [login {error-enable | mschap}]
Displays AAA authentication information.
show aaa groups
Displays the AAA server group configuration.
show running-config aaa [all]
Displays the AAA configuration in the running configuration.
show startup-config aaa
Displays the AAA configuration in the startup configuration.
Example 1: show aaa authentication
switch# show aaa authentication login error-enable disabled switch#Example 3: show running config aaa
switch# show running-config aaa all !Time: Fri Nov 15 11:22:13 2013 version 5.2(1)SK1(2.1) aaa authentication login default local aaa authorization ssh-publickey default local aaa authorization ssh-certificate default local aaa accounting default local aaa user default-role aaa authentication login default fallback error local aaa authentication login console fallback error local no aaa authentication login error-enable no aaa authentication login mschap enable no aaa authentication login mschapv2 enable no aaa authentication login chap enable no aaa authentication login ascii-authentication no radius-server directed-request switch#
