Identification of Subscribers Using the PPPoE Remote Circuit Identifier

You can enable the router to capture and format a vendor-specific tag containing a PPPoE remote circuit ID transmitted from a digital subscriber line access multiplexer (DSLAM) device. The router can then send this value to a Remote Authentication Dial-In User Service (RADIUS) server or to a Layer 2 Tunneling Protocol (L2TP) network server (LNS) to uniquely identify subscriber locations.

This feature is supported on all modules on which you can configure PPPoE interfaces. The feature is particularly useful in Ethernet-based Broadband Remote Access Server (B-RAS) configurations as a means of uniquely identifying subscribers connected to the router on a single Ethernet link.

For detailed configuration instructions, see Configuring PPPoE Remote Circuit ID Capture.

Application

When a connection between an E Series router and a DSLAM is on an ATM interface, subscribers are typically assigned an ATM PVC to communicate with the router. Each ATM PVC is created on a different ATM 1483 subinterface. When a RADIUS server in this configuration sends messages to the router containing the NAS-Port-Id [87] RADIUS attribute, each ATM 1483 subinterface produces a unique NAS-Port-Id that can differentiate subscribers on the ATM link.

By contrast, when the connection between the router and the DSLAM is on an Ethernet interface that does not use either virtual LANs (VLANs) or stacked VLANs (S-VLANs), the NAS-Port-Id value is the same for all subscribers on the Ethernet link. Enabling the router to capture the remote circuit ID sent from the DSLAM and use it as a RADIUS or L2TP attribute facilitates the process of identifying individual subscribers on an Ethernet link.

PPPoE Remote Circuit ID Capture

When you enable capture of the PPPoE remote circuit ID by issuing the pppoe remote-circuit-id command, the E Series router captures the remote circuit ID value if it is sent from the DSLAM. The PPPoE intermediate agent on the DSLAM appends a vendor-specific tag containing the remote circuit ID to the existing PPPoE PADI or PADR packet and sends this packet to the E Series router. The PPPoE remote circuit ID value can be a maximum of 64 characters. The router stores this value on the line module on which the PPPoE interface is configured.

PPPoE Remote Circuit ID Format

By default, the router formats the captured PPPoE remote circuit ID to include only the agent-circuit-id suboption (suboption 1) of the PPPoE intermediate agent tags sent from the DSLAM. To configure a nondefault format for the captured PPPoE remote circuit ID, you can use one of the radius remote-circuit-id-format commands listed in Table 34.

For more information about configuring the format of the PPPoE remote circuit ID value, see radius remote-circuit-id-format.

Remote Circuit ID Delimiter

If the format of the PPPoE remote circuit ID consists of two or more components, the router uses a # character by default to delimit the components. Optionally, you can use the radius remote-circuit-id-delimiter command to configure a nondefault delimiter character (for example, ! or %) to separate multiple components in the PPPoE remote circuit ID value. For information about how to use this command, see radius remote-circuit-id-delimiter.

Format for dsl-forum-1 Keyword

When you specify the radius remote-circuit-id-format command with the dsl-forum-1 keyword, the router appends the agent-circuit-id suboption value to an interface specifier that is consistent with the recommended format in the DSL Forum Technical Report (TR)-101—Migration to Ethernet-Based DSL Aggregation (April 2006).

The format of the PPPoE remote circuit ID when you use the dsl-forum-1 keyword is as follows:

dslForum1InterfaceSpecifier#agent-circuit-id

where:

• dslForum1InterfaceSpecifier is the interface specifier in dsl-forum-1 format
• # is the default delimiter character
• agent-circuit-id is the agent-circuit-id suboption (suboption 1) of the PPPoE intermediate agent tags sent from the DSLAM

If the DSLAM transmits empty data for agent-circuit-id, the router appends the value 0/0/0/0/0/0 to dslForum1InterfaceSpecifier.

To obtain the value for dslForum1InterfaceSpecifier, the router translates an internally generated interface specifier into the format for the dsl-forum-1 keyword, using the following conventions:

• The dsl-forum-1 format for ATM interfaces is atm slot/adapter/port:vpi.vci
• The dsl-forum-1 format for Ethernet interfaces is eth slot/adapter/port:svlanId.vlanId
• For the E120 or the E320 routers, the router uses the actual adapter value (0 or 1) in the dsl-forum-1 format. For ERX14xx models, ERX7xx models, and the ERX310 router, which do not support an adapter value, the router sets the adapter value to 0 (zero).
• For Ethernet interfaces that use VLANs but do not use S-VLANs, the router sets the svlanId value to 4096 and uses the actual vlanId value in the dsl-forum-1 format.
• For Ethernet interfaces that use neither S-VLANs nor VLANs, the router sets both the svlanId value and the vlanId value to 4096 in the dsl-forum-1 format.
• The router ignores subinterface values for ATM and Ethernet interfaces in the translated dsl-forum-1 format.

  Note: The format of the interface specifier that the router generates internally is different from the interface specifier format that you use to configure interfaces on the router. For information about the interface types and specifiers to use when configuring interfaces on E Series routers, see Interface Types and Specifiers in JunosE Command Reference Guide.

Format Examples for dsl-forum-1 Keyword

Table 35 provides several examples of how the router uses the conventions described in Format for dsl-forum-1 Keyword to translate internally generated interface specifiers into the format of the dslForum1InterfaceSpecifier value. The examples in the table use adapter 1 for interfaces on an E120 or E320 router, and adapter 0 (no adapter value) for interfaces on ERX14xx models, ERX7xx models, and the ERX310 router.

Use by RADIUS or L2TP

Enabling the router to capture and format the PPPoE remote circuit ID sent from the DSLAM has no effect by itself. To use the PPPoE remote circuit ID value, you must send it to a RADIUS server, to an L2TP network server (LNS), or to both by doing one or more of the following:

• Issue the radius override calling-station-id remote-circuit-id command to substitute the remote circuit ID value for the standard Calling-Station-Id [31] RADIUS attribute.
• Issue the radius override nas-port-id remote-circuit-id command to substitute the remote circuit ID value for the standard NAS-Port-Id [87] RADIUS attribute.
• Issue the aaa tunnel calling-number-format command to generate L2TP Calling Number attribute value pair (AVP) 22 in a descriptive format that includes either or both of the agent-circuit-id (suboption 1) and agent-remote-id (suboption 2) suboptions of the PPPoE intermediate agent tags.

For more information about configuring RADIUS and L2TP on E Series routers, see the JunosE Broadband Access Configuration Guide.

System Event Log

You can use the radiusSendAttributes system event log category to troubleshoot applications that use PPPoE remote circuit ID capture. The radiusSendAttributes event category logs RADIUS attributes added to outbound RADIUS requests.

You can also use the log severity debug pppoeControlPacket command to configure a packet trace log for a PPPoE interface that includes the PPPoE remote circuit ID value captured on that interface. For information about how to use the log severity debug pppoeControlPacket command, see Troubleshooting PPPoE Interfaces.

For information about how to log system events, see Overview of System Logging.

Related Documentation

• Configuring PPPoE Remote Circuit ID Capture
• Monitoring the RADIUS Override Settings
• Monitoring Tunnel Parameters Configured for L2TP Tunnel Definitions
• Troubleshooting PPPoE Interfaces
• log severity