Intelligent Services Gateway Configuration Guide, Cisco IOS XE Release 3S (Cisco ASR 1000)
Enabling ISG to Interact with External Policy Servers
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Enabling ISG to Interact with External Policy Servers

Enabling ISG to Interact with External Policy Servers

Intelligent Services Gateway (ISG) is a software feature set that provides a structured framework in which edge devices can deliver flexible and scalable services to subscribers. This document describes how to enable the ISG to retrieve session policies or accept dynamic updates to session policies from external policy servers.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and 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 module.

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.

Restrictions for ISG Interaction with External Policy Servers

The ISG and external policy servers should be available in the same virtual routing and forwarding (VRF) instance.

Information About ISG Interaction with External Policy Servers

Initial and Dynamic Authorization

ISG works with external devices, referred to as policy servers that store per-subscriber and per-service information. ISG supports two models of interaction between the ISG and external policy servers: initial authorization and dynamic authorization.

In the initial authorization model, ISG must retrieve policies from the external policy server at specific points in a session. In this model, the external policy server is typically an authentication, authorization, and accounting (AAA) server that uses RADIUS. ISG is the RADIUS client. Instead of a AAA server, some systems use a RADIUS proxy component that converts to other database protocols, such as Lightweight Directory Access Protocol (LDAP).

The dynamic authorization model allows the external policy server to dynamically send policies to ISG. These operations can be initiated in-band by subscribers (through service selection) or through the actions of an administrator, or applications can change policies on the basis of some algorithm (for example, change session quality of service (QoS) at a certain time of day). This model is facilitated by the Change of Authorization (CoA) RADIUS extension. CoA introduces peer-to-peer capability to RADIUS that enables ISG and the external policy server to act as the RADIUS client and server respectively.

Triple Key Authentication for ISG

Triple key authentication is a method of authenticating users based on their username, password, and location after ISG redirects them to the Cisco Service Management Engine (SME) portal. The SME server provides the location based on the source IP address of the subscriber being authenticated. Before the Triple Key Authentication Support feature was introduced, users were authenticated only on the basis of the username and password (two-key authentication). The Triple Key Authentication Support feature also eases migration from Service Selection Gateway (SSG) to an ISG platform because SSG uses triple key authentication.

For SSG, the Cisco Subscriber Edge Services Manager (SESM) server populates RADIUS attribute 31 (calling-station ID) in the user-login request that it sends to the SSG with a string containing the subscriber’s location. The SSG then includes this location string in the access-request message that it sends to the RADIUS server where the login is authenticated based on the username, password, and location string.

With ISG triple key authentication, the ISG sends the location string within a Cisco vendor-specific attribute (VSA) that is included in the access-request message to the RADIUS server.

The location information is received from SME as Cisco VSA 250. This location information is included in session authentication requests, session accounting requests from the ISG, and prepaid authorization requests.

The table below shows the Cisco vendor-specific non-AVPair attribute used for triple key authentication.

Table 1 Cisco Vendor-Specific Non-AVPair Attribute

Sub-AttrID

Attribute Type

Value

Function

Example

Used in

250

account-info

L<location- string>

Third key in triple key authentication

LWiFiHotSpot001

Acc-Req CoA Req Accounting

How to Enable ISG to Interact with External Policy Servers

Configuring ISG as a AAA Client

Perform this task to configure AAA method lists and enable ISG to retrieve policies from a AAA server. This task must be performed for both initial and dynamic authorization models.

Before You Begin

The servers and server groups referenced by the AAA methods must be configured.

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    aaa authentication login {default | list-name} method1 [method2...]

    4.    aaa authentication ppp {default | list-name} method1 [method2...]

    5.    aaa authorization {network | exec | commands level | reverse-access | configuration} {default | list-name} [method1 [method2...]]

    6.    aaa authorization subscriber-service {default | list-name} method1 [method2...]

    7.    aaa accounting {auth-proxy | system | network | exec | connection | commands level} {default | list-name} [vrf vrf-name] {start-stop | stop-only | none} [broadcast] group group-name

    8.    end


DETAILED STEPS
     Command or ActionPurpose
    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 aaa authentication login {default | list-name} method1 [method2...]


    Example:
    Router(config)# aaa authentication login PPP1 group radius
     

    Specifies one or more AAA authentication methods to be used at login.

     
    Step 4 aaa authentication ppp {default | list-name} method1 [method2...]


    Example:
    Router(config)# aaa authentication ppp default group radius
     

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

     
    Step 5 aaa authorization {network | exec | commands level | reverse-access | configuration} {default | list-name} [method1 [method2...]]


    Example:
    Router(config)# aaa authorization network NET1 radius
     

    Specifies one or more AAA authorization methods to be used for restricting subscriber access to a network.

     
    Step 6 aaa authorization subscriber-service {default | list-name} method1 [method2...]


    Example:
    Router(config)# aaa authorization subscriber-service default radius
     

    Specifies one or more AAA authorization methods for ISG to use in providing a service.

     
    Step 7 aaa accounting {auth-proxy | system | network | exec | connection | commands level} {default | list-name} [vrf vrf-name] {start-stop | stop-only | none} [broadcast] group group-name


    Example:
    Router(config)# aaa accounting network default start-stop group radius
     

    Enables AAA accounting of requested services for billing or security purposes.

     
    Step 8 end


    Example:
    Router(config)# end
     

    Exits global configuration mode.

     

    Configuring ISG as a AAA Server

    Dynamic authorization allows a policy server to dynamically send policies to ISG. Perform this task to configure ISG as a AAA server and enable dynamic authorization.

    SUMMARY STEPS

      1.    enable

      2.    configure terminal

      3.    aaa server radius dynamic-author

      4.    client {name | ip-address} [key [0 | 7] word] [vrf vrf-id]

      5.    port port-number

      6.    server-key [0 | 7] word

      7.    auth-type {all | any | session-key}

      8.    ignore {server-key | session-key}

      9.    end


    DETAILED STEPS
       Command or ActionPurpose
      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 aaa server radius dynamic-author


      Example:
      Router(config)# aaa server radius dynamic-author
       

      Configures ISG as a AAA server and enters dynamic authorization local server configuration mode.

       
      Step 4 client {name | ip-address} [key [0 | 7] word] [vrf vrf-id]


      Example:
      Router(config-locsvr-da-radius)# client 10.76.86.90 key cisco
       

      Specifies a client with which ISG will be communicating.

       
      Step 5 port port-number


      Example:
      Router(config-locsvr-da-radius)# port 1600
       

      Specifies the RADIUS server port.

      • Default is 1700.
       
      Step 6 server-key [0 | 7] word


      Example:
      Router(config-locsvr-da-radius)# server-key cisco
       

      Specifies the encryption key shared with the RADIUS client.

       
      Step 7 auth-type {all | any | session-key}


      Example:
      Router(config-locsvr-da-radius)# auth-type all
       

      Specifies the attributes to be used for session authorization.

       
      Step 8 ignore {server-key | session-key}


      Example:
      Router(config-locsvr-da-radius)# ignore session-key
       

      Configures ISG to ignore the shared encryption key or attribute 151.

       
      Step 9 end


      Example:
      Router(config-locsvr-da-radius)# end
       

      Exits dynamic authorization local server configuration mode.

       

      Enabling the Location VSA for Triple Key Authentication

      Perform this task to enable ISG to include the location VSA in authentication and accounting requests.

      SUMMARY STEPS

        1.    enable

        2.    configure terminal

        3.    aaa new-model

        4.    radius-server vsa send accounting

        5.    radius-server vsa send authentication

        6.    end


      DETAILED STEPS
         Command or ActionPurpose
        Step 1 enable


        Example:
        Router> enable
         

        Enters privileged EXEC mode.

        • Enter your password if prompted.
         
        Step 2 configure terminal


        Example:
        Router# configure terminal
         

        Enters global configuration mode.

         
        Step 3 aaa new-model


        Example:
        Router(config)# aaa new-model
         

        Enables AAA.

         
        Step 4 radius-server vsa send accounting


        Example:
        Router(config)# radius-server vsa send accounting
         

        Enables ISG to recognize and use accounting VSAs as defined by RADIUS attribute 26.

         
        Step 5 radius-server vsa send authentication


        Example:
        Router(config)# radius-server vsa send authentication
         

        Enables ISG to recognize and use authentication VSAs as defined by RADIUS attribute 26.

         
        Step 6 end


        Example:
        Router(config)# end
         

        Exits to privileged EXEC mode.

         

        Configuration Examples for ISG Interaction with External Policy Servers

        Example: Enabling ISG to Interact with External Policy Servers

        The following example shows how to configure ISG as a AAA client.

        
        aaa group server radius CAR_SERVER
         server 10.100.2.36 auth-port 1812 acct-port 1813
        
        aaa authentication login default none
        aaa authentication login IP_AUTHEN_LIST group CAR_SERVER
        aaa authentication ppp default group CAR_SERVER
        aaa authorization network default group CAR_SERVER 
        aaa authorization subscriber-service default local group radius 
        aaa accounting network default start-stop group CAR_SERVER
        

        The following example shows how to configure ISG as a AAA server.

        aaa server radius dynamic-author
          client 10.76.86.90 server-key cisco
          port 1600
          server-key cisco 
          auth-type all
          ignore session-key
        

        Example: Enabling the Location VSA for Triple Key Authentication

        The following example shows how to enable ISG to use VSAs for accounting and authentication.

        aaa new-model
        radius-server vsa send accounting
        radius-server vsa send authentication

        The following example shows an authentication record with the session information, including the location attribute. You can display this output by using the debug radius accounting command or the gw-accounting syslog command.

        Device# debug radius accounting
        
        *Feb  5 01:20:50.413: RADIUS/ENCODE: Best Local IP-Address 10.0.1.1 for Radius-Server 10.0.1.2
        *Feb  5 01:20:50.425: RADIUS(0000000F): Send Access-Request to 10.0.1.2:1645 id 1645/5, len 107
        *Feb  5 01:20:50.425: RADIUS:  authenticator 4D 86 12 BC BD E9 B4 9B - CB FC B8 7E 4C 8F B6 CA
        *Feb  5 01:20:50.425: RADIUS:  Vendor, Cisco       [26]  19  
        *Feb  5 01:20:50.425: RADIUS:   ssg-account-info   [250] 13  "LWiFiHotSpot001"   
        *Feb  5 01:20:50.425: RADIUS:  Calling-Station-Id  [31]  16  "AAAA.BBBB.CCCC"
        *Feb  5 01:20:50.425: RADIUS:  User-Name           [1]   7   "george"
        *Feb  5 01:20:50.425: RADIUS:  User-Password       [2]   18  *
        *Feb  5 01:20:50.425: RADIUS:  NAS-Port-Type       [61]  6   Virtual                   [5]
        *Feb  5 01:20:50.425: RADIUS:  NAS-Port            [5]   6   0                         
        *Feb  5 01:20:50.425: RADIUS:  NAS-Port-Id         [87]  9   "0/0/0/0"
        *Feb  5 01:20:50.425: RADIUS:  NAS-IP-Address      [4]   6   10.0.1.1                  
        *Feb  5 01:20:50.425: RADIUS(0000000F): Started 5 sec timeout
        *Feb  5 01:20:50.425: RADIUS: Received from id 1645/5 10.0.1.2:1645, Access-Accept, len 68
        *Feb  5 01:20:50.425: RADIUS:  authenticator 49 A1 2C 7F C5 E7 9D 1A - 97 B3 E3 72 F3 EA 56 56
        *Feb  5 01:20:50.425: RADIUS:  Vendor, Cisco       [26]  17  
        *Feb  5 01:20:50.425: RADIUS:   ssg-account-info   [250] 11  "S10.0.0.2"
        *Feb  5 01:20:50.425: RADIUS:  Vendor, Cisco       [26]  31  
        *Feb  5 01:20:50.425: RADIUS:   Cisco AVpair       [1]   25  "accounting-list=default"
        *Feb  5 01:20:50.433: RADIUS(0000000F): Received from id 1645/5
        *Feb  5 01:20:50.437: RADIUS/ENCODE(0000000F):Orig. component type = Iedge IP SIP
        *Feb  5 01:20:50.437: RADIUS(0000000F): Config NAS IP: 0.0.0.0
        *Feb  5 01:20:50.437: RADIUS(0000000F): sending

        Additional References

        Related Documents

        Related Topic

        Document Title

        Cisco IOS commands

        Cisco IOS Master Commands List, All Releases

        ISG commands

        Cisco IOS Intelligent Services Gateway Command Reference

        AAA configuration tasks

        Part 1, “Authentication, Authorization, and Accounting (AAA),” Cisco IOS XE Security Configuration Guide

        AAA commands

        Cisco IOS Security Command Reference

        MIBs

        MIB

        MIBs Link

        No new or modified MIBs are supported.

        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

        Technical Assistance

        Description

        Link

        The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

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

        Feature Information for ISG Interaction with External Policy Servers

        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 2 Feature Information for ISG Interaction with External Policy Servers

        Feature Name

        Releases

        Feature Information

        ISG—Policy Control Policy Server CoA

        Cisco IOS XE Release 3.3SG

        This feature provides ISG support for the RADIUS Change of Authorization (CoA) extension, which facilitates dynamic authorization.

        This feature was integrated into Cisco IOS XE Release 3.3SG.

        ISG—Session Lifecycle Packet of Disconnect (POD)

        Cisco IOS XE Release 3.3SG

        This feature enables an external policy server to terminate an ISG session when it receives a RADIUS Packet of Disconnect (POD).