Configuring AAA

This chapter describes how to configure authentication, authorization, and accounting (AAA) on Cisco NX-OS devices.

This chapter includes the following sections:

About AAA

This section includes information about AAA on Cisco NX-OS devices.

AAA Security Services

The AAA feature allows you to verify the identity of, grant access to, and track the actions of users managing a Cisco NX-OS device. Cisco NX-OS devices support Remote Access Dial-In User Service (RADIUS) or Terminal Access Controller Access Control System Plus (TACACS+) protocols.

Based on the user ID and password combination that you provide, Cisco NX-OS devices perform local authentication or authorization using the local database or remote authentication or authorization using one or more AAA servers. A preshared secret key provides security for communication between the Cisco NX-OS device and AAA servers. You can configure a common secret key for all AAA servers or for only a specific AAA server.

AAA security provides the following services:

Authentication
Identifies users, including login and password dialog, challenge and response, messaging support, and, depending on the security protocol that you select, encryption.

Authentication is the process of verifying the identity of the person or device accessing the Cisco NX-OS device, which is based on the user ID and password combination provided by the entity trying to access the Cisco NX-OS device. Cisco NX-OS devices allow you to perform local authentication (using the local lookup database) or remote authentication (using one or more RADIUS or TACACS+ servers).

Authorization
Provides access control.AAA authorization is the process of assembling a set of attributes that describe what the user is authorized to perform. Authorization in the Cisco NX-OS software is provided by attributes that are downloaded from AAA servers. 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.
Accounting
Provides the method for collecting information, logging the information locally, and sending the information to the AAA server for billing, auditing, and reporting.

The accounting feature tracks and maintains a log of every management session used to access the Cisco NX-OS device. 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.


Note

The Cisco NX-OS software supports authentication, authorization, and accounting independently. For example, you can configure authentication and authorization without configuring accounting.

Benefits of Using AAA

AAA provides the following benefits:

  • Increased flexibility and control of access configuration

  • Scalability

  • Standardized authentication methods, such as RADIUS and TACACS+

  • Multiple backup devices

Remote AAA Services

Remote AAA services provided through RADIUS and TACACS+ protocols have the following advantages over local AAA services:

  • It is easier to manage user password lists for each Cisco NX-OS device in the fabric.

  • AAA servers are already deployed widely across enterprises and can be easily used for AAA services.

  • You can centrally manage the accounting log for all Cisco NX-OS devices in the fabric.

  • It is easier to manage user attributes for each Cisco NX-OS device in the fabric than using the local databases on the Cisco NX-OS devices.

AAA Server Groups

You can specify remote AAA servers for authentication, authorization, and accounting using server groups. A server group is a set of remote AAA servers that implements the same AAA protocol. The purpose of a server group is to provide for failover servers in case a remote AAA server fails to respond. If the first remote server in the group fails to respond, the next remote server in the group is tried until one of the servers sends a response. If all the AAA servers in the server group fail to respond, then that server group option is considered a failure. If required, you can specify multiple server groups. If the Cisco NX-OS device encounters errors from the servers in the first group, it tries the servers in the next server group.

AAA Service Configuration Options

The AAA configuration in Cisco NX-OS devices is service based, which means that you can have separate AAA configurations for the following services:

  • User Telnet or Secure Shell (SSH) login authentication

  • Console login authentication

  • User management session accounting

This table provides the related CLI command for each AAA service configuration option.

Table 1. AAA Service Configuration Commands

AAA Service Configuration Option

Related Command

Telnet or SSH login

aaa authentication login default

Console login

aaa authentication login console

User session accounting

aaa accounting default

You can specify the following authentication methods for the AAA services:

All RADIUS servers

Uses the global pool of RADIUS servers for authentication.

Specified server groups

Uses specified RADIUS, TACACS+, or LDAP server groups you have configured for authentication.

Local

Uses the local username or password database for authentication.

None

Specifies that no AAA authentication be used.


Note

If you specify the all RADIUS servers method, rather than a specified server group method, the Cisco NX-OS device chooses the RADIUS server from the global pool of configured RADIUS servers, in the order of configuration. Servers from this global pool are the servers that can be selectively configured in a RADIUS server group on the Cisco NX-OS device.

This table shows the AAA authentication methods that you can configure for the AAA services.

Table 2. AAA Authentication Methods for AAA Services

AAA Service

AAA Methods

Console login authentication

Server groups, local, and none

User login authentication

Server groups, local, and none

User management session accounting

Server groups and local


Note

For console login authentication, user login authentication, and user management session accounting, the Cisco NX-OS device tries each option in the order specified. The local option is the default method when other configured options fail. You can disable the local option for the console or default login by using the no aaa authentication login { console | default } fallback error local command.

Authentication and Authorization Process for User Login

Figure 1. Authorization and Authentication Flow for User Login. This figure shows a flow chart of the authentication and authorization process for user login.

The following list explains the process:

  • When you log in to the required Cisco NX-OS device, you can use the Telnet, SSH, or console login options.

  • When you have configured the AAA server groups using the server group authentication method, the Cisco NX-OS device sends an authentication request to the first AAA server in the group as follows:

    • If the AAA server fails to respond, the next AAA server is tried and so on until the remote server responds to the authentication request.

    • If all AAA servers in the server group fail to respond, the servers in the next server group are tried.

    • If all configured methods fail, the local database is used for authentication, unless fallback to local is disabled for the console login.

  • If the Cisco NX-OS device successfully authenticates you through a remote AAA server, then the following possibilities apply:

    • If the AAA server protocol is RADIUS, then user roles specified in the cisco-av-pair attribute are downloaded with an authentication response.

    • If the AAA server protocol is TACACS+, then another request is sent to the same server to get the user roles specified as custom attributes for the shell.

  • If your username and password are successfully authenticated locally, the Cisco NX-OS device logs you in and assigns you the roles configured in the local database.


Note

"No more server groups left" means that there is no response from any server in all server groups. "No more servers left" means that there is no response from any server within this server group.

AES Password Encryption and Master Encryption Keys

You can enable strong, reversible 128-bit Advanced Encryption Standard (AES) password encryption, also known as type-6 encryption. To start using type-6 encryption, you must enable the AES password encryption feature and configure a master encryption key, which is used to encrypt and decrypt passwords.

After you enable AES password encryption and configure a master key, all existing and newly created clear-text passwords for supported applications (currently RADIUS and TACACS+) are stored in type-6 encrypted format, unless you disable type-6 password encryption. You can also configure Cisco NX-OS to convert all existing weakly encrypted passwords to type-6 encrypted passwords.

Licensing Requirements for AAA

The following table shows the licensing requirements for this feature:

Product

License Requirement

Cisco NX-OS

AAA requires no license. Any feature not included in a license package is bundled with the nx-os image and is provided at no extra charge to you. For an explanation of the Cisco NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide.

Prerequisites for AAA

Remote AAA servers have the following prerequisites:

  • Ensure that at least one RADIUS, TACACS+, or LDAP server is reachable through IP.

  • Ensure that the Cisco NX-OS device is configured as a client of the AAA servers.

  • Ensure that the secret key is configured on the Cisco NX-OS device and the remote AAA servers.

  • Ensure that the remote server responds to AAA requests from the Cisco NX-OS device.

Guidelines and Limitations for AAA

AAA has the following guidelines and limitations:

  • If you have a user account configured on the local Cisco NX-OS device that has the same name as a remote user account on an AAA server, the Cisco NX-OS software applies the user roles for the local user account to the remote user, not the user roles configured on the AAA server.

  • Cisco Nexus 9000 Series switches support the aaa authentication login ascii-authentication command only for TACACS+ (and not for RADIUS).

  • If you modify the default login authentication method (without using the local keyword), the configuration overrides the console login authentication method. To explicitly configure the console authentication method, use the aaa authentication login console {group group-list [none] | local | none} command.

Default Settings for AAA

This table lists the default settings for AAA parameters.

Table 3. Default AAA Parameter Settings

Parameters

Default

Console authentication method

local

Default authentication method

local

Login authentication failure messages

Disabled

CHAP authentication

Disabled

MSCHAP authentication

Disabled

Default accounting method

local

Accounting log display length

250 KB

Configuring AAA

This section describes the tasks for configuring AAA on Cisco NX-OS devices.


Note

If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature might differ from the Cisco IOS commands that you would use.


Note

Cisco Nexus 9K Series switches support the CLI command, aaa authentication login ascii-authentication, only for TACAAS+, but not for RADIUS. Ensure that you have disabled aaa authentication login ascii-authentication switch so that the default authentication, PAP, is enabled. Otherwise, you will see syslog errors.

Process for Configuring AAA

Follow these steps to configure AAA authentication and accounting:

  1. If you want to use remote RADIUS, TACACS+, or LDAP servers for authentication, configure the hosts on your Cisco NX-OS device.

  2. Configure console login authentication methods.

  3. Configure default login authentication methods for user logins.

  4. Configure default AAA accounting default methods.

Configuring Console Login Authentication Methods

This section describes how to configure the authentication methods for the console login.

The authentication methods include the following:

  • Global pool of RADIUS servers

  • Named subset of RADIUS, TACACS+, or LDAP servers

  • Local database on the Cisco NX-OS device

  • Username only (none)

The default method is local, but you have the option to disable it .


Note

The group radius and group server-name forms of the aaa authentication command refer to a set of previously defined RADIUS servers. Use the radius-server host command to configure the host servers. Use the aaa group server radius command to create a named group of servers.


Note
If you perform a password recovery when remote authentication is enabled, local authentication becomes enabled for console login as soon as the password recovery is done. As a result, you can log into the Cisco NX-OS device through the console port using the new password. After login, you can continue to use local authentication, or you can enable remote authentication after resetting the admin password configured at the AAA servers. For more information about the password recovery process, see the Cisco Nexus 9000 Series NX-OS Troubleshooting Guide.

Before you begin

Configure RADIUS, TACACS+, or LDAP server groups, as needed.

SUMMARY STEPS

  1. configure terminal
  2. aaa authentication login console {group group-list [none] | local | none}
  3. exit
  4. (Optional) show aaa authentication
  5. (Optional) copy running-config startup-config

DETAILED STEPS

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters configuration mode.

Step 2

aaa authentication login console {group group-list [none] | local | none}

Example:

switch(config)# aaa authentication login console group radius

Configures login authentication methods for the console.

The group-list argument consists of a space-delimited list of group names. The group names are the following:

radius
Uses the global pool of RADIUS servers for authentication.
named-group
Uses a named subset of RADIUS, TACACS+, or LDAP servers for authentication.

The local method uses the local database for authentication, and the none method specifies that no AAA authentication be used.

The default console login method is local , which is used when no methods are configured or when all the configured methods fail to respond, unless fallback to local is disabled for the console login .

Step 3

exit

Example:

switch(config)# exit
switch#

Exits configuration mode.

Step 4

(Optional) show aaa authentication

Example:

switch# show aaa authentication
(Optional)

Displays the configuration of the console login authentication methods.

Step 5

(Optional) copy running-config startup-config

Example:

switch# copy running-config startup-config
(Optional)

Copies the running configuration to the startup configuration.

Configuring Default Login Authentication Methods

The authentication methods include the following:

  • Global pool of RADIUS servers

  • Named subset of RADIUS, TACACS+, or LDAP servers

  • Local database on the Cisco NX-OS device

  • Username only

The default method is local, but you have the option to disable it .

Before you begin

Configure RADIUS, TACACS+, or LDAP server groups, as needed.

SUMMARY STEPS

  1. configure terminal
  2. aaa authentication login default {group group-list [none] | local | none}
  3. exit
  4. (Optional) show aaa authentication
  5. (Optional) copy running-config startup-config

DETAILED STEPS

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters configuration mode.

Step 2

aaa authentication login default {group group-list [none] | local | none}

Example:

switch(config)# aaa authentication login default group radius

Configures the default authentication methods.

The group-list argument consists of a space-delimited list of group names. The group names are the following:

  • radius —Uses the global pool of RADIUS servers for authentication.

  • named-group—Uses a named subset of RADIUS, TACACS+, or LDAP servers for authentication.

The local method uses the local database for authentication, and the none method specifies that no AAA authentication be used. The default login method is local , which is used when no methods are configured or when all the configured methods fail to respond, unless fallback to local is disabled for the console login .

You can configure one of the following:

  • AAA authentication groups

  • AAA authentication groups with no authentication

  • Local authentication

  • No authentication

Note

 

The local keyword is not supported (and is not required) when configuring AAA authentication groups because local authentication is the default if remote servers are unreachable. For example, if you configure aaa authentication login default group g1 , local authentication is tried if you are unable to authenticate using AAA group g1. In contrast, if you configure aaa authentication login default group g1 none , no authentication is performed if you are unable to authenticate using AAA group g1.

Step 3

exit

Example:

switch(config)# exit
switch#

Exits configuration mode.

Step 4

(Optional) show aaa authentication

Example:

switch# show aaa authentication
(Optional)

Displays the configuration of the default login authentication methods.

Step 5

(Optional) copy running-config startup-config

Example:

switch# copy running-config startup-config
(Optional)

Copies the running configuration to the startup configuration.

Disabling Fallback to Local Authentication

By default, if remote authentication is configured for console or default login and all AAA servers are unreachable (resulting in an authentication error), the Cisco NX-OS device falls back to local authentication to ensure that users are not locked out of the device. However, you can disable fallback to local authentication in order to increase security.


Caution

Disabling fallback to local authentication can lock your Cisco NX-OS device, forcing you to perform a password recovery in order to gain access. To prevent being locked out of the device, we recommend that you disable fallback to local authentication for only the default login or the console login, not both.

Before you begin

Configure remote authentication for the console or default login.

SUMMARY STEPS

  1. configure terminal
  2. no aaa authentication login {console | default} fallback error local
  3. (Optional) exit
  4. (Optional) show aaa authentication
  5. (Optional) copy running-config startup-config

DETAILED STEPS

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters configuration mode.

Step 2

no aaa authentication login {console | default} fallback error local

Example:

switch(config)# no aaa authentication login console fallback error local

Disables fallback to local authentication for the console or default login if remote authentication is configured and all AAA servers are unreachable.

The following message appears when you disable fallback to local authentication: 

“WARNING!!! Disabling fallback can lock your switch.”

Step 3

(Optional) exit

Example:

switch(config)# exit
switch#
 (Optional)

Exits configuration mode.

Step 4

(Optional) show aaa authentication

Example:

switch# show aaa authentication
(Optional)

Displays the configuration of the console and default login authentication methods.

Step 5

(Optional) copy running-config startup-config

Example:

switch# copy running-config startup-config
(Optional)

Copies the running configuration to the startup configuration.

Enabling the Default User Role for AAA Authentication

You can allow remote users who do not have a user role to log in to the Cisco NX-OS device through a RADIUS or TACACS+ remote authentication server using a default user role. When you disable the AAA default user role feature, remote users who do not have a user role cannot log in to the device.

SUMMARY STEPS

  1. configure terminal
  2. aaa user default-role
  3. exit
  4. (Optional) show aaa user default-role
  5. (Optional) copy running-config startup-config

DETAILED STEPS

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters configuration mode.

Step 2

aaa user default-role

Example:

switch(config)# aaa user default-role

Enables the default user role for AAA authentication. The default is enabled.

You can disable the default user role feature by using the no form of this command.

Step 3

exit

Example:

switch(config)# exit
switch#

Exits configuration mode.

Step 4

(Optional) show aaa user default-role

Example:

switch# show aaa user default-role
(Optional)

Displays the AAA default user role configuration.

Step 5

(Optional) copy running-config startup-config

Example:

switch# copy running-config startup-config
 (Optional)

Copies the running configuration to the startup configuration.

Enabling Login Authentication Failure Messages

When you log in, the login is processed by rolling over to the local user database if the remote AAA servers do not respond. In such cases, the following messages display on the user’s terminal if you have enabled login failure messages: 

Remote AAA servers unreachable; local authentication done.
Remote AAA servers unreachable; local authentication failed.

SUMMARY STEPS

  1. configure terminal
  2. aaa authentication login error-enable
  3. exit
  4. (Optional) show aaa authentication
  5. (Optional) copy running-config startup-config

DETAILED STEPS

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters configuration mode.

Step 2

aaa authentication login error-enable

Example:

switch(config)# aaa authentication login error-enable

Enables login authentication failure messages. The default is disabled.

Step 3

exit

Example:

switch(config)# exit
switch#

Exits configuration mode.

Step 4

(Optional) show aaa authentication

Example:

switch# show aaa authentication
(Optional)

Displays the login failure message configuration.

Step 5

(Optional) copy running-config startup-config

Example:

switch# copy running-config startup-config
 (Optional)

Copies the running configuration to the startup configuration.

Enabling CHAP Authentication

The Cisco NX-OS software supports the Challenge Handshake Authentication Protocol (CHAP), a challenge-response authentication protocol that uses the industry-standard Message Digest (MD5) hashing scheme to encrypt responses. You can use CHAP for user logins to a Cisco NX-OS device through a remote authentication server (RADIUS or TACACS+).

By default, the Cisco NX-OS device uses Password Authentication Protocol (PAP) authentication between the Cisco NX-OS device and the remote server. If you enable CHAP, you need to configure your RADIUS or TACACS+ server to recognize the CHAP vendor-specific attributes (VSAs).


Note

Cisco Nexus 9K Series switches support the CLI command, aaa authentication login ascii-authentication, only for TACAAS+, but not for RADIUS. Ensure that you have disabled aaa authentication login ascii-authentication switch so that the default authentication, PAP, is enabled. Otherwise, you will see syslog errors. For example: 

2017 Jun 14 16:14:15 N9K-1 %RADIUS-2-RADIUS_NO_AUTHEN_INFO: ASCII authentication not supported
2017 Jun 14 16:14:16 N9K-1 %AUTHPRIV-3-SYSTEM_MSG: pam_aaa:Authentication failed from 192.168.12.34 - dcos_sshd[16804]

This table shows the RADIUS and TACACS+ VSAs required for CHAP.

Table 4. CHAP RADIUS and TACACS+ VSAs

Vendor-ID Number

Vendor-Type Number

VSA

Description

311

11

CHAP-Challenge

Contains the challenge sent by an AAA server to a CHAP user. It can be used in both Access-Request and Access-Challenge packets.

211

11

CHAP-Response

Contains the response value provided by a CHAP user in response to the challenge. It is used only in Access-Request packets.

Before you begin

Disable AAA ASCII authentication for logins.

SUMMARY STEPS

  1. configure terminal
  2. no aaa authentication login ascii-authentication
  3. aaa authentication login chap enable
  4. (Optional) exit
  5. (Optional) show aaa authentication login chap
  6. (Optional) copy running-config startup-config

DETAILED STEPS

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters configuration mode.

Step 2

no aaa authentication login ascii-authentication

Example:

switch(config)# no aaa authentication login ascii-authentication

Disables ASCII authentication.

Step 3

aaa authentication login chap enable

Example:

switch(config)# aaa authentication login chap enable

Enables CHAP authentication. The default is disabled.

Note

 

You cannot enable both CHAP and MSCHAP or MSCHAP V2 on your Cisco NX-OS device.

Step 4

(Optional) exit

Example:

switch(config)# exit
switch#
 (Optional)

Exits configuration mode.

Step 5

(Optional) show aaa authentication login chap

Example:

switch# show aaa authentication login chap
(Optional)

Displays the CHAP configuration.

Step 6

(Optional) copy running-config startup-config

Example:

switch# copy running-config startup-config
(Optional)

Copies the running configuration to the startup configuration.

Enabling MSCHAP or MSCHAP V2 Authentication

Microsoft Challenge Handshake Authentication Protocol (MSCHAP) is the Microsoft version of CHAP. The Cisco NX-OS software also supports MSCHAP Version 2 (MSCHAP V2). You can use MSCHAP for user logins to a Cisco NX-OS device through a remote authentication server (RADIUS or TACACS+). MSCHAP V2 only supports user logins to a Cisco NX-OS device through remote authentication RADIUS servers. If you configure a TACACS+ group with MSCHAP V2, the AAA default login authentication uses the next configured method, or the local method, if no other server group is configured.


Note

The Cisco NX-OS software may display the following message:

“ Warning: MSCHAP V2 is supported only with Radius.”

This warning message is informational only and does not affect MSCHAP V2 operation with RADIUS.

By default, the Cisco NX-OS device uses Password Authentication Protocol (PAP) authentication between the Cisco NX-OS device and the remote server. If you enable MSCHAP or MSCHAP V2, you need to configure your RADIUS server to recognize the MSCHAP and MSCHAP V2 vendor-specific attributes (VSAs).

This table shows the RADIUS VSAs required for MSCHAP.

Table 5. MSCHAP and MSCHAP V2 RADIUS VSAs

Vendor-ID Number

Vendor-Type Number

VSA

Description

311

11

MSCHAP-Challenge

Contains the challenge sent by an AAA server to an MSCHAP or MSCHAP V2 user. It can be used in both Access-Request and Access-Challenge packets.

211

11

MSCHAP-Response

Contains the response value provided by an MSCHAP or MSCHAP V2 user in response to the challenge. It is only used in Access-Request packets.

Before you begin

Disable AAA ASCII authentication for logins.

SUMMARY STEPS

  1. configure terminal
  2. no aaa authentication login ascii-authentication
  3. aaa authentication login {mschap | mschapv2} enable
  4. exit
  5. (Optional) show aaa authentication login {mschap | mschapv2}
  6. (Optional) copy running-config startup-config

DETAILED STEPS

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters configuration mode.

Step 2

no aaa authentication login ascii-authentication

Example:

switch(config)# no aaa authentication login ascii-authentication

Disables ASCII authentication.

Step 3

aaa authentication login {mschap | mschapv2} enable

Example:

switch(config)# aaa authentication login mschap enable

Enables MSCHAP or MSCHAP V2 authentication. The default is disabled.

Note

 

You cannot enable both MSCHAP and MSCHAP V2 on your Cisco NX-OS device.

Step 4

exit

Example:

switch(config)# exit
switch#

Exits configuration mode.

Step 5

(Optional) show aaa authentication login {mschap | mschapv2}

Example:

switch# show aaa authentication login mschap
(Optional)

Displays the MSCHAP or MSCHAP V2 configuration.

Step 6

(Optional) copy running-config startup-config

Example:

switch# copy running-config startup-config
(Optional)

Copies the running configuration to the startup configuration.

Configuring AAA Accounting Default Methods

Cisco NX-OS software supports TACACS+ and RADIUS methods for accounting. Cisco NX-OS devices report user activity to TACACS+ or RADIUS security servers in the form of accounting records. Each accounting record contains accounting attribute-value (AV) pairs and is stored on the AAA server.

When you activate AAA accounting, the Cisco NX-OS device reports these attributes as accounting records, which are then stored in an accounting log on the security server.

You can create default method lists defining specific accounting methods, which include the following:

RADIUS server group
Uses the global pool of RADIUS servers for accounting.
Specified server group
Uses a specified RADIUS or TACACS+ server group for accounting.
Local
Uses the local username or password database for accounting.

Note

If you have configured server groups and the server groups do not respond, by default, the local database is used for authentication.

Before you begin

Configure RADIUS or TACACS+ server groups, as needed.

SUMMARY STEPS

  1. configure terminal
  2. aaa accounting default {group group-list | local}
  3. exit
  4. (Optional) show aaa accounting
  5. (Optional) copy running-config startup-config

DETAILED STEPS

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters configuration mode.

Step 2

aaa accounting default {group group-list | local}

Example:

switch(config)# aaa accounting default group radius

Configures the default accounting method.

The group-list argument consists of a space-delimited list of group names. The group names are the following:

  • radius —Uses the global pool of RADIUS servers for accounting.

  • named-group—Uses a named subset of TACACS+ or RADIUS servers for accounting.

The local method uses the local database for accounting.

The default method is local , which is used when no server groups are configured or when all the configured server groups fail to respond.

Step 3

exit

Example:

switch(config)# exit
switch#

Exits configuration mode.

Step 4

(Optional) show aaa accounting

Example:

switch# show aaa accounting
(Optional)

Displays the configuration AAA accounting default methods.

Step 5

(Optional) copy running-config startup-config

Example:

switch# copy running-config startup-config
(Optional)

Copies the running configuration to the startup configuration.

Using AAA Server VSAs with Cisco NX-OS Devices

You can use vendor-specific attributes (VSAs) to specify Cisco NX-OS user roles and SNMPv3 parameters on AAA servers.

About VSAs

The Internet Engineering Task Force (IETF) draft standard specifies a method for communicating VSAs between the network access server and the RADIUS server. The IETF uses attribute 26. VSAs allow vendors to support their own extended attributes that are not suitable for general use. The Cisco RADIUS implementation supports one vendor-specific option using the format recommended in the specification. The Cisco vendor ID is 9, and the supported option is vendor type 1, which is named cisco-av-pair. The value is a string with the following format: 

protocol : attribute separator value *

The protocol is a Cisco attribute for a particular type of authorization, the separator is = (equal sign) for mandatory attributes, and * (asterisk) indicates optional attributes.

When you use RADIUS servers for authentication on a Cisco NX-OS device, the RADIUS protocol directs the RADIUS server to return user attributes, such as authorization information, along with authentication results. This authorization information is specified through VSAs.

VSA Format

The following VSA protocol options are supported by the Cisco NX-OS software:

Shell
Protocol used in access-accept packets to provide user profile information.
Accounting
Protocol used in accounting-request packets. If a value contains any white spaces, put it within double quotation marks.

The following attributes are supported by the Cisco NX-OS software:

roles

Lists all the roles assigned to the user. The value field is a string that stores the list of group names delimited by white space. For example, if you belong to role network-operator and network-admin, the value field would be network-operator network-admin. This subattribute is sent in the VSA portion of the Access-Accept frames from the RADIUS server, and it can only be used with the shell protocol value. These examples use the roles attribute: 

shell:roles=network-operator network-admin 
shell:roles*network-operator network-admin

The following examples show the roles attribute as supported by FreeRADIUS: 

Cisco-AVPair = shell:roles=\network-operator network-admin\ 
Cisco-AVPair = shell:roles*\network-operator network-admin\

Note

When you specify a VSA as shell:roles*"network-operator network-admin" or "shell:roles*\"network-operator network-admin\"", this VSA is flagged as an optional attribute and other Cisco devices ignore this attribute.

accountinginfo
Stores accounting information in addition to the attributes covered by a standard RADIUS accounting protocol. This attribute is sent only in the VSA portion of the Account-Request frames from the RADIUS client on the switch, and it can only be used with the accounting protocol-related PDUs.

Specifying Cisco NX-OS User Roles and SNMPv3 Parameters on AAA Servers

You can use the VSA cisco-av-pair on AAA servers to specify user role mapping for the Cisco NX-OS device using this format: 

shell:roles="roleA roleB …"

If you do not specify the role option in the cisco-av-pair attribute, the default user role is network-operator.

You can also specify your SNMPv3 authentication and privacy protocol attributes as follows: 

shell:roles="roleA roleB..." snmpv3:auth=SHA priv=AES-128

The SNMPv3 authentication protocol options are SHA and MD5. The privacy protocol options are AES-128 and DES. If you do not specify these options in the cisco-av-pair attribute, MD5 and DES are the default authentication protocols.

Monitoring and Clearing the Local AAA Accounting Log

The Cisco NX-OS device maintains a local log for the AAA accounting activity. You can monitor this log and clear it.

SUMMARY STEPS

  1. show accounting log [size | last-index | start-seqnum number | start-time year month day hh : mm : ss]
  2. (Optional) clear accounting log [logflash]

DETAILED STEPS

  Command or Action Purpose

Step 1

show accounting log [size | last-index | start-seqnum number | start-time year month day hh : mm : ss]

Example:

switch# show accounting log

Displays the accounting log contents. By default, the command output contains up to 250,000 bytes of the accounting log. You can use the size argument to limit command output. The range is from 0 to 250000 bytes. You can also specify a starting sequence number or a starting time for the log output.The range of the starting index is from 1 to 1000000. Use the last-index keyword to display the value of the last index number in the accounting log file.

Step 2

(Optional) clear accounting log [logflash]

Example:

switch# clear aaa accounting log
 (Optional)

Clears the accounting log contents. The logflash keyword clears the accounting log stored in the logflash.

Verifying the AAA Configuration

To display AAA configuration information, perform one of the following tasks:

Command

Purpose

show aaa accounting

Displays AAA accounting configuration.

show aaa authentication [login {ascii-authentication | chap | error-enable | mschap | mschapv2}]

Displays AAA authentication login configuration 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.

Configuration Examples for AAA

The following example shows how to configure AAA: 


aaa authentication login default group radius 
aaa authentication login console group radius 
aaa accounting default group radius

Additional References for AAA

This section includes additional information related to implementing AAA.

Related Documents

Related Topic

Document Title

Cisco NX-OS Licensing

Cisco NX-OS Licensing Guide

Standards

Standards

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

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MIBs

MIBs

MIBs Link

MIBs related to AAA

To locate and download supported MIBs, go to the following URL:

ftp://ftp.cisco.com/pub/mibs/supportlists/nexus9000/Nexus9000MIBSupportList.html