Per IP Subscriber DHCP Triggered RADIUS Accounting

Per IP Subscriber DHCP Triggered RADIUS Accounting is implemented in a distributed networking environment, based on the following client-server components:

• Access Interface--Used by subscribers to operate on a Cisco 7600 router.
• DHCP Server--Grants permission to the DHCP client to use a particular IP address for a specified lease time.
• AAA Server--Transmits secure START and STOP accounting messages.

After the periodic timer is configured on the unit under test (UUT), the AAA module on the UUT sends an interim periodic update to the RADIUS server.

• RADIUS Server--Receives and responds to accounting requests.

The figure below shows how the Access Client, referred to as the “aaa-access-client” module, is initialized to serve as a client of the RADIUS accounting server. The module is independent of existing DHCP RADIUS Accounting modules.

The Access Client comprises two sub-modules that enable improved IP session awareness, tracking, and reporting functionality:

• Access-Subscriber Management module (Access-Acct-Mgmt): Invoked by a successful DHCP IP assignment, this sub-module generates a unique AAA ID for each subscriber that combines with the DHCP unique ID to track an accounting session.
• Access-Subscriber Accounting Management (Access-Acct-Update): Invoked by the AAA server, this sub-module collects subscriber statistics and periodically reports on the accounting session.

• Benefits of Per IP Subscriber DHCP Triggered RADIUS Accounting
  

When a client with an Access Type of interface is configured for Per IP Subscriber RADIUS Accounting, the statistics collection and reporting mechanism can be invoked by the DHCP module. A successful DHCP IP assignment or release triggers three types of accounting events via the Access Client module:

1. RADIUS accounting start: An Accounting Start packet, ACCT_START, is sent to the accounting server to flag the start of service delivery, the type of service being delivered, and the user it is being delivered to.
2. RADIUS accounting interim-update: An Accounting Interim Update packet, ACCT_UPDATE, is sent to the accounting server to flag an ongoing client association and IP session activity.
3. RADIUS accounting stop: An Accounting Stop packet, ACCT_STOP, is sent to the accounting server to flag the end of service delivery, the type of service that was delivered and optional statistics such as elapsed time, and input and output packets.

Accounting requests, for any packet type, are submitted to the RADIUS accounting server via the network, and are acknowledged in these forms:

• RADIUS Accounting Response (START)
• RADIUS Interim Accounting Response
• RADIUS Accounting Response (STOP)

The figure below shows the AAA Access Client process flow and how the client interacts with the required modules.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    interface type number [name-tag] access

4.    encapsulation dot1q vlan-id [native]

5.    ip address ip-address mask [secondary]

6.    accounting dhcp source-ip aaa list method-list-name

7.    end

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	interface type number [name-tag] access Example: Router(config)# interface gigabitethernet 1/0/1.2 access	Configures an interface type and enters access interface configuration mode.
Step 4	encapsulation dot1q vlan-id [native] Example: Router(config-subif)# encapsulation dot1q 102	Enables IEEE 802.1q encapsulation of traffic on a specified subinterface in a virtual LAN (VLAN).
Step 5	ip address ip-address mask [secondary] Example: Router(config-subif)# ip address 10.0.2.1 255.255.255.0	Sets a primary or secondary IP address for an interface.
Step 6	accounting dhcp source-ip aaa list method-list-name Example: Router(config-subif)# accounting dhcp source-ip aaa list default	Enables the Per IP Subscriber DHCP RADIUS Accounting feature for DCHP clients, and configures accounting method lists that define the way accounting will be performed and the sequence in which methods are performed. Use the method-list-name argument to apply the accounting method list to a subinterface.
Step 7	end Example: Router(config-subif)# end	Ends the current configuration session and returns to privileged EXEC mode.