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

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