# Subscriber Management Procedure

Figure 15 shows a subscriber management environment that includes an external DHCP server, a RADIUS server, the SRC software, and the DHCP external server application running on the E Series router.

The E Series router DHCP external server application is used with other JunosE features to provide subscriber management. Using the router’s DHCP external server application for subscriber management enables you to take advantage of the following features:

- Profile assignment—A dynamic subscriber interface profile is associated with a specific source address by the router’s packet detect feature.
- Dynamic subscriber interface packet detection and inactivity timer—Subscriber interfaces are dynamically created based on packet information that is identified by the packet detection feature. The inactivity timer determines when a dynamic subscriber interface expires and needs to be deleted.
- DHCP external server application—DHCP packets are examined to determine the state of subscribers.

  Figure 15: DHCP External Server

In Figure 15, the subscriber requests an address from the DHCP server. The E Series router DHCP external server application monitors all DHCP communications between the subscriber and the DHCP server. After the subscriber receives an IP address, the subscriber can access the Internet and use the value-added services provided by the SRC software. The following list describes the various procedures performed in the subscriber management environment:

- Subscriber PC—Requests an IP address from the DHCP server
- E Series router
  - Monitors DHCP traffic between the subscriber and the DHCP server:
    - Identifies the subscriber’s IP address, MAC address, giaddr, and client identifier
    - Extracts the lease time, creates a shadow lease, and starts its own lease timer that is associated with the subscriber
  - Determines the subscriber is active when the subscriber sends a packet after receiving an IP address from DHCP. The router then:
    - Processes the subscriber’s IP address by using a route map
    - Extracts the dynamic subscriber interface profile (optional)

      The router uses the profile to provide authentication, authorization, accounting, and address assignment. RADIUS uses the profile to obtain information for the subscriber’s IP interface.

    - Creates the subscriber’s dynamic subscriber interface (DSI)
  - If the SRC software is configured, the router also alerts the SRC software that the subscriber’s DSI and address exist.
  - The DHCP external server application continues to monitor all traffic between the subscriber and the DHCP server, and periodically resets the shadow lease it originally created when the subscriber first requested an IP address. When the subscriber disconnects, the shadow lease eventually expires, at which time the E Series router performs the following:
    - Deletes the DSI
    - Alerts the SRC software that the DSI has been deleted
    - Alerts the SRC software that the subscriber’s address has been deleted
- SRC software—Provides enhanced services to the subscriber.

## Configuring Subscriber Management with an External DHCP Server

To configure subscriber management for clients by using an external DHCP server, as in Figure 15, use the following procedure on E Series routers:

1. Enable the DHCP external server application.
   host1(config)#service dhcp-external
2. Specify each DHCP server for which to monitor traffic. You can specify a maximum of four DHCP servers.
   host1(config)#ip dhcp-external server-address 10.10.10.1
3. Configure a default policy for subscribers, using a previously configured classifier group.
   host1(config)#ip policy-list filterAll host1(config-policy-list)#classifier-group filterGroupA host1(config-policy-list-classifier-group)#filter host1(config-policy-list-classifier-group)#exit host1(config-policy-list)#exit
4. Configure a dynamic subscriber interface policy.
   host1(config)#profile disableUser host1(config-profile)#ip policy input filterAll host1(config-profile)#ip policy output filterAll host1(config-profile)#exit
5. Configure a route map.
   host1(config)#route-map routeMapWest21 host1(config-route-map)#set ip interface-profile disableUser host1(config-route-map)#exit
6. Enable autoconfiguration mode.
   host1(config)#interface gigabitEthernet 12/0 host1(config-if)#ip address 192.168.1.1 255.255.255.0 host1(config-if)#ip auto-configure ip-subscriber include-primary host1(config-if)#ip route-map ip-subscriber routeMapWest21 host1(config-if)#ip auto-detect ip-subscriber host1(config-profile)#exit