RADIUS Attribute Value Screening

The RADIUS Attribute Value Screening feature allows users to configure a list of “accept” or “reject” RADIUS attributes on the network access server (NAS) for purposes such as authorization or accounting.

If a NAS accepts and processes all RADIUS attributes received in an Access-Accept packet, unwanted attributes may be processed, creating a problem for wholesale providers who do not control their customers’ authentication, authorization, and accounting (AAA) servers. For example, there may be attributes that specify services to which the customer has not subscribed, or there may be attributes that may degrade service for other wholesale dial users. The ability to configure the NAS to restrict the use of specific attributes has therefore become a requirement for many users.

The RADIUS Attribute Value Screening feature should be implemented in one of the following ways:

  • To allow the NAS to accept and process all standard RADIUS attributes for a particular purpose, except for those on a configured reject list
  • To allow the NAS to reject (filter out) all standard RADIUS attributes for a particular purpose, except for those on a configured accept list

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Prerequisites for RADIUS Attribute Value Screening

Before configuring a RADIUS accept or reject list, you must enable AAA.

Restrictions for RADIUS Attribute Value Screening

NAS Requirements

To enable this feature, your NAS should be configured for authorization with RADIUS groups.

Accept or Reject Lists Limitations

The two filters used to configure accept or reject lists are mutually exclusive; therefore, a user can configure only one access list or one reject list for each purpose, per server group.

Vendor-Specific Attributes

This feature does not support vendor-specific attribute (VSA) screening; however, a user can specify attribute 26 (Vendor-Specific) in an accept or reject list, which accepts or reject all VSAs.

Required Attributes Screening Recommendation

It is recommended that users do not reject the following required attributes:

  • For authorization:
    • 6 (Service-Type)
    • 7 (Framed-Protocol)
  • For accounting:
    • 4 (NAS-IP-Address)
    • 40 (Acct-Status-Type)
    • 41 (Acct-Delay-Time)
    • 44 (Acct-Session-ID)

If an attribute is required, the rejection is refused, and the attribute is allowed to pass through.


Note

The user does not receive an error at the point of configuring a reject list for required attributes because the list does not specify a purpose--authorization or accounting. The server determines whether an attribute is required when it is known what the attribute is to be used for.

Information About RADIUS Attribute Value Screening

The RADIUS Attribute Value Screening feature provides the following benefits:

  • Users can configure an accept or reject list consisting of a selection of attributes on the NAS for a specific purpose so unwanted attributes are not accepted and processed.
  • Users may wish to configure an accept list that includes only relevant accounting attributes, thereby reducing unnecessary traffic and allowing users to customize their accounting data.

How to Screen RADIUS Attributes

Configuring RADIUS Attribute Value Screening

To configure a RADIUS attribute accept or reject list for authorization or accounting, use the following commands:

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    Router(config)# aaa authentication ppp default

    4.    Router(config)# aaa authorization network default group group-name

    5.    Router(config)# aaa group server radius group-name

    6.    Router(config-sg-radius)# server ip-address

    7.    Router(config-sg-radius)# authorization [accept | reject] listname

    8.    Router(config-sg-radius)# exit

    9.    Router(config)# radius-server host {hostname | ip-address} [key string

    10.    Router(config)# radius-server attribute list listname

    11.    Router(config-sg-radius)# attribute value1 [value2 [value3...]]


DETAILED STEPS
      Command or Action Purpose
    Step 1 enable


    Example: 
    Router> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.
     
    Step 2 configure terminal


    Example: 
    Router# configure terminal
     

    Enters global configuration mode.

     
    Step 3 Router(config)# aaa authentication ppp default

    Example: 
                
              group
             group-name
     

    Specifies one or more AAA authentication methods for use on serial interfaces running PPP.

     
    Step 4 Router(config)# aaa authorization network default group group-name  

    Sets parameters that restrict network access to the user.

     
    Step 5 Router(config)# aaa group server radius group-name  

    Groups different RADIUS server hosts into distinct lists and distinct methods.

     
    Step 6 Router(config-sg-radius)# server ip-address  

    Configures the IP address of the RADIUS server for the group server,

     
    Step 7 Router(config-sg-radius)# authorization [accept | reject] listname

    Example: 
    and/or


    Example: 
    Router(config-sg-radius)#
 accounting [accept | reject] listname
     

    Specifies a filter for the attributes that are returned in an Access-Accept packet from the RADIUS server.

    and/or

    Specifies a filter for the attributes that are to be sent to the RADIUS server in an accounting request.

    Note   

    The accept keyword indicates that all attributes are rejected except for the attributes specified in the listname. The reject keyword indicates that all attributes are accepted except for the attributes specified in the listname and all standard attributes.

     
    Step 8 Router(config-sg-radius)# exit  

    Exits server-group configuration mode.

     
    Step 9 Router(config)# radius-server host {hostname | ip-address} [key string  

    Specifies a RADIUS server host.

     
    Step 10 Router(config)# radius-server attribute list listname  

    Defines the list name given to the set of attributes defined in the attribute command.

    Note   

    The listname must be the same as the listname defined in Step 5.

     
    Step 11 Router(config-sg-radius)# attribute value1 [value2 [value3...]]  

    Adds attributes to the configured accept or reject list.

    Note   

    This command can be used multiple times to add attributes to an accept or reject list.

     

    Verifying RADIUS Attribute Value Screening

    To verify an accept or reject list, use one of the following commands in privileged EXEC mode:

    Command

    Purpose

    		 
    Router# debug aaa accounting

    Displays information on accountable events as they occur.

    		 
    Router# debug aaa authentication

    Displays information on AAA authentication.

    		 
    Router# show radius statistics

    Displays the RADIUS statistics for accounting and authentication packets.

    Configuration Examples for RADIUS Attribute Value Screening

    Authorization Accept Example

    The following example shows how to configure an accept list for attribute 6 (Service-Type) and attribute 7 (Framed-Protocol); all other attributes (including VSAs) are rejected for RADIUS authorization. 

    aaa new-model
aaa authentication ppp default group radius-sg
aaa authorization network default group radius-sg
aaa group server radius radius-sg
server 10.1.1.1
authorization accept min-author
!
radius-server host 10.1.1.1 key mykey1
radius-server attribute list min-author
attribute 6-7

    Accounting Reject Example

    The following example shows how to configure a reject list for attribute 66 (Tunnel-Client-Endpoint) and attribute 67 (Tunnel-Server-Endpoint); all other attributes (including VSAs) are accepted for RADIUS accounting. 

    aaa new-model
aaa authentication ppp default group radius-sg
aaa authorization network default group radius-sg
aaa group server radius radius-sg
server 10.1.1.1
accounting reject tnl-x-endpoint
!
radius-server host 10.1.1.1 key mykey1
radius-server attribute list tnl-x-endpoint
attribute 66-67

    Authorization Reject and Accounting Accept Example

    The following example shows how to configure a reject list for RADIUS authorization and configure an accept list for RADIUS accounting. Although you cannot configure more than one accept or reject list per server group for authorization or accounting, you can configure one list for authorization and one list for accounting per server group.

    aaa new-model
aaa authentication ppp default group radius-sg
aaa authorization network default group radius-sg
aaa group server radius radius-sg
server 10.1.1.1
authorization reject bad-author
accounting accept usage-only
!
radius-server host 10.1.1.1 key mykey1
radius-server attribute list usage-only
attribute 1,40,42-43,46
!
radius-server attribute list bad-author
attribute 22,27-28,56-59

    Rejecting Required Attributes Example

    The following example shows debug output for the debug aaa accounting command. In this example, required attributes 44, 40, and 41 have been added to the reject list “standard.”

    Router# debug aaa authorization
AAA/ACCT(6): Accounting method=radius-sg (radius)
RADIUS: attribute 44 cannot be rejected
RADIUS: attribute 61 rejected
RADIUS: attribute 31 rejected
RADIUS: attribute 40 cannot be rejected
RADIUS: attribute 41 cannot be rejected

    Additional References

    The following sections provide references related to the RADIUS Attribute Value Screening feature.

    Related Documents

    Related Topic

    Document Title

    RADIUS

    “ Configuring RADIUS ” feature module.

    Other security features

    Cisco IOS XE Security Configuration Guide: Securing User Services , Release 2

    Security commands

    Cisco IOS Security Command Reference

    Standards

    Standard

    Title

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

    --

    MIBs

    MIB

    MIBs Link

    None.

    To locate and download MIBs for selected platforms, Cisco software releases, and feature sets, use Cisco MIB Locator found at the following URL:

    http:/​/​www.cisco.com/​go/​mibs

    RFCs

    RFC

    Title

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

    --

    Technical Assistance

    Description

    Link

    The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies.

    To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.

    Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

    http:/​/​www.cisco.com/​cisco/​web/​support/​index.html

    Feature Information for RADIUS Attribute Value Screening

    The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

    Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

    Table 1 Feature Information for RADIUS Attribute Value Screening

    Feature Name

    Releases

    Feature Information

    RADIUS Attribute Value Screening

    Cisco IOS XE Release 2.1

    The RADIUS Attribute Value Screening feature allows users to configure a list of “accept” or “reject” RADIUS attributes on the network access server (NAS) for purposes such as authorization or accounting.

    In Cisco IOS XE Release 2.1, this feature was introduced on the Cisco ASR 1000 Series Aggregation Services Routers

    The following commands were introduced or modified by this feature: accounting (server-group), authorization (server-group), attribute (server-group), radius-server attribute list