RADIUS Configuration Guide Cisco IOS XE Release 3S
AAA Server Groups
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AAA Server Groups

Configuring a device to use authentication, authorization, and accounting (AAA) server groups provides a way to group existing server hosts. Grouping existing server hosts allows you to select a subset of the configured server hosts and use them for a particular service. Configuring deadtime within a server group allows you to direct AAA traffic to separate groups of servers that have different operational characteristics. This feature module describes how to configure AAA server groups and the deadtimer.

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.

Information About AAA Server Groups

AAA Server Groups

Configuring the device to use AAA server groups provides a way to group existing server hosts. Grouping existing server hosts allows you to select a subset of the configured server hosts and use them for a particular service. A server group is used with a global server-host list. The server group lists the IP addresses of the selected server hosts.

Server groups can also include multiple host entries for the same server, as long as each entry has a unique identifier. The combination of an IP address and a UDP port number creates a unique identifier, allowing different ports to be individually defined as RADIUS hosts providing a specific AAA service. This unique identifier enables RADIUS requests to be sent to different UDP ports on a server at the same IP address. If two different host entries on the same RADIUS server are configured for the same service—for example, accounting—the second host entry that is configured acts as a failover backup to the first one. If the first host entry fails to provide accounting services, the network access server tries the second host entry configured on the same device for accounting services. (The RADIUS host entries are tried in the order in which they are configured.)

AAA Server Groups with a Deadtimer

After you configure a server host with a server name, you can use the deadtime command to configure each server per server group. Configuring deadtime within a server group allows you to direct AAA traffic to separate groups of servers that have different operational characteristics.

Configuring deadtime is not limited to a global configuration. A separate timer is attached to each server host in every server group. Therefore, when a server is found to be unresponsive after numerous retransmissions and timeouts, the server is assumed to be dead. The timers attached to each server host in all server groups are triggered. In essence, the timers are checked and subsequent requests to a server (once it is assumed to be dead) are directed to alternate timers, if configured. When the network access server receives a reply from the server, it checks and stops all configured timers (if running) for that server in all server groups.

If the timer has expired, the server to which the timer is attached is assumed to be alive. This becomes the only server that can be tried for later AAA requests using the server groups to which the timer belongs.


Note


Because one server has different timers and might have different deadtime values configured in the server groups, the same server might, in the future, have different states (dead and alive) at the same time.



Note


To change the state of a server, you must start and stop all configured timers in all server groups.


The size of the server group will be slightly increased because of the addition of new timers and the deadtime attribute. The overall impact of the structure depends on the number and size of the server groups and how the servers are shared among server groups in a specific configuration.

How to Configure AAA Server Groups

Configuring AAA Server Groups

To define a server host with a server group name, enter the following commands in global configuration mode. The listed server must exist in global configuration mode.

Before You Begin

Each server in the group must be defined previously using the radius-server host command.

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    radius-server host {hostname | ip-address} [auth-port port-number] [acct-port port-number] [timeout seconds] [retransmit retries] [key string] [alias {hostname | ip-address}]

    4.    aaa group server {radius | tacacs+} group-name

    5.    server ip-address [auth-port port-number] [acct-port port-number]

    6.    end


DETAILED STEPS
      Command or Action Purpose
    Step 1 enable


    Example:
    Device> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.
     
    Step 2 configure terminal


    Example:
    Device# configure terminal
     

    Enters global configuration mode.

     
    Step 3 radius-server host {hostname | ip-address} [auth-port port-number] [acct-port port-number] [timeout seconds] [retransmit retries] [key string] [alias {hostname | ip-address}]


    Example:
    Device(config)# radius-server host 10.45.1.2
     

    Specifies and defines the IP address of the server host before configuring the AAA server group.

     
    Step 4 aaa group server {radius | tacacs+} group-name


    Example:
    Device(config)# aaa group server radius group1
     

    Defines the AAA server group with a group name.

    • All members of a group must be the same type, that is, RADIUS or TACACS+. This command puts the device in server group RADIUS configuration mode.
     
    Step 5 server ip-address [auth-port port-number] [acct-port port-number]


    Example:
    Device(config-sg-radius)# server 172.16.1.1 acct-port 1616
     

    Associates a particular RADIUS server with the defined server group.

    • Each security server is identified by its IP address and UDP port number.
    • Repeat this step for each RADIUS server in the AAA server group.
     
    Step 6 end


    Example:
    Device(config-sg-radius)# end
     

    Exits server group RADIUS configuration mode and returns to privileged EXEC mode.

     

    Configuring AAA Server Groups with a Deadtimer

    SUMMARY STEPS

      1.    enable

      2.    configure terminal

      3.    aaa group server radius group

      4.    deadtime minutes

      5.    end


    DETAILED STEPS
        Command or Action Purpose
      Step 1 enable


      Example:
      Device> enable
       

      Enables privileged EXEC mode.

      • Enter your password if prompted.
       
      Step 2 configure terminal


      Example:
      Device# configure terminal
       

      Enters global configuration mode.

       
      Step 3 aaa group server radius group


      Example:
      Device(config)# aaa group server radius group1
       

      Defines a RADIUS type server group and enters server group RADIUS configuration mode.

       
      Step 4 deadtime minutes


      Example:
      Device(config-sg-radius)# deadtime 1
       

      Configures and defines a deadtime value in minutes.

      Note   

      Local server group deadtime overrides the global configuration. If the deadtime vlaue is omitted from the local server group configuration, it is inherited from the master list.

       
      Step 5 end


      Example:
      Device(config-sg-radius)# end
       

      Exits server group RADIUS configuration mode and returns to privileged EXEC mode.

       

      Configuration Examples for AAA Server Groups

      Examples: AAA Server Groups

      The following example shows how to create server group radgroup1 with three different RADIUS server members, each using the default authentication port (1645) and accounting port (1646):

      aaa group server radius radgroup1
       server 172.16.1.11 
       server 172.17.1.21 
       server 172.18.1.31 
      

      The following example shows how to create server group radgroup2 with three RADIUS server members, each with the same IP address but with unique authentication and accounting ports:

      aaa group server radius radgroup2
       server 172.16.1.1 auth-port 1000 acct-port 1001
       server 172.16.1.1 auth-port 2000 acct-port 2001
       server 172.16.1.1 auth-port 3000 acct-port 3001

      Example: Multiple RADIUS Server Entries Using AAA Server Groups

      The following example shows how to configure the network access server to recognize two different RADIUS server groups. One of these groups, group1, has two different host entries on the same RADIUS server configured for the same services. The second host entry configured acts as failover backup to the first one. Each group is individually configured for the deadtime; the deadtime for group 1 is one minute, and the deadtime for group 2 is two minutes.


      Note


      In cases where both global commands and server commands are used, the server command takes precedence over the global command.


      ! This command enables AAA.
      aaa new-model
      ! The next command configures default RADIUS parameters.
      aaa authentication ppp default group group1
      ! The following commands define the group1 RADIUS server group and associate servers
      ! with it and configures a deadtime of one minute.
      aaa group server radius group1
       server 10.1.1.1 auth-port 1645 acct-port 1646
       server 10.2.2.2 auth-port 2000 acct-port 2001
       deadtime 1
      ! The following commands define the group2 RADIUS server group and associate servers
      ! with it and configures a deadtime of two minutes.
      aaa group server radius group2
       server 10.2.2.2 auth-port 2000 acct-port 2001
       server 10.3.3.3 auth-port 1645 acct-port 1646
       deadtime 2
      ! The following set of commands configures the RADIUS attributes for each host entry
      ! associated with one of the defined server groups.
      radius-server host 10.1.1.1 auth-port 1645 acct-port 1646
      radius-server host 10.2.2.2 auth-port 2000 acct-port 2001
      radius-server host 10.3.3.3 auth-port 1645 acct-port 1646

      Additional References

      Related Documents

      Related Topic

      Document Title

      Cisco IOS commands

      Cisco IOS Master Command List, All Releases

      AAA and RADIUS commands

      Cisco IOS Security Command Reference

      RADIUS attributes

      RADIUS Attributes Configuration Guide (part of the Securing User Services Configuration Library)

      AAA

      Authentication, Authorization, and Accounting Configuration Guide (part of the Securing User Services Configuration Library)

      L2TP, VPN, or VPDN

      Dial Technologies Configuration Guide and VPDN Configuration Guide

      Modem configuration and management

      Dial Technologies Configuration Guide

      RADIUS port identification for PPP

      Wide-Area Networking Configuration Guide

      RFCs

      RFC

      Title

      RFC 2138

      Remote Authentication Dial-In User Service (RADIUS)

      RFC 2139

      RADIUS Accounting

      RFC 2865

      RADIUS

      RFC 2867

      RADIUS Accounting Modifications for Tunnel Protocol Support

      RFC 2868

      RADIUS Attributes for Tunnel Protocol Support

      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 AAA Server Groups

      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 AAA Server Groups

      Feature Name

      Releases

      Feature Information

      AAA Server Group

      12.0(5)T

      12.1(3)T

      12.1(4)T

      12.2(2)T

      12.2(27)SBA

      12.2(33)SRC

      Cisco IOS XE Release 2.1

      Configuring the device to use AAA server groups provides a way to group existing server hosts. This allows you to select a subset of the configured server hosts and use them for a particular service. A server group is used with a global server-host list. The server group lists the IP addresses of the selected server hosts.

      The following commands were introduced or modified: aaa group server radius, aaa group server tacacs+, and server (RADIUS).

      AAA Server Group Enhancements

      12.1(2)T

      12.2(2)T

      12.2(27)SBA

      12.2(33)SRC

      Cisco IOS XE Release 2.1

      AAA Server Group Enhancements enables the full configuration of a server in a server group.

      AAA Server Group Deadtimer

      12.1(2)T

      12.2(2)T

      12.2(27)SBA

      12.2(33)SRC

      Cisco IOS XE Release 2.1

      Configuring deadtime within a server group allows you to direct AAA traffic to separate groups of servers that have different operational characteristics.

      The following commands were introduced or modified: deadtime.