# Configuring PPPoE over ATM

This section provides an example of a common PPPoE over ATM configuration.

See the following resources for additional information:

- Configuring ATM —Provides detailed information about ATM technology and line interface module capabilities.
- Configuring Bridged Ethernet—Provides configuration information about Bridged Ethernet, which allows multiple upper-layer interface types (IP and PPPoE) to be simultaneously multiplexed over the same interface.
- Configuring Dynamic Interfaces—Provides detailed information about configuring ATM to support dynamic interfaces.
- Configuring Upper-Layer Protocols over Static Ethernet Interfaces

To configure PPPoE over ATM:

1. Configure a physical interface.
   host1(config)#interface atm 0/1
2. Configure the ATM 1483 subinterface.
   host1(config-if)#interface atm 0/1.20
3. Configure a PVC by specifying the vcd (virtual circuit descriptor), the vpi (virtual path identifier), the vci (virtual channel identifier), and the encapsulation type.
   host1(config-if)#atm pvc 10 22 100 aal5snap
4. Select PPPoE as the encapsulation method.
   host1(config-subif)#encapsulation pppoe

5. Do one of the following to configure the maximum number of PPPoE sessions (subinterfaces) supported on the interface:

   - Configure the maximum number of PPPoE sessions on a per-interface basis.
     host1(config-if)#pppoe sessions 128
   - Configure the maximum number of PPPoE sessions on a per-subscriber basis by overriding the current PPPoE maximum session value with the PPPoE maximum session value returned by the RADIUS server in the Max-Clients-Per-Interface vendor-specific attribute (VSA) [26-143] in Access-Accept messages.
     host1(config-if)#pppoe max-session-vsa override
6. Create a PPPoE subinterface.
   host1(config-subif)#interface atm 0/1.20.1
7. Select PPP as the encapsulation method.
   host1(config-subif)#encapsulation ppp
8. (Optional) Configure maximum transfer unit (MTU) parameters.
   host1(config-if)#pppoe mtu 1380
9. (Optional) Configure an access concentrator (AC) name on the PPPoE interface.
   host1(config-subif)#pppoe acname CYM9876
10. (Optional) Set up the router to prevent a client from establishing more than one session using the same MAC address.

    When the duplicate protection feature is enabled, multiple IWF PPPoE sessions that contain the same MAC address are still processed and can access network services until the maximum number of PPPoE sessions configured per major interface (configured using the pppoe sessions command) is reached. For more information about how IWF PPPoE sessions with duplicate addresses are handled, see Processing of IWF PPPoE Sessions with Duplicate MAC Addresses.

    host1(config-subif)#pppoe duplicate-protection
11. Assign an IP address and subnet mask to the PVC.
    host1(config-subif)#ip address 192.32.10.20 255.255.255.0
12. (Optional) Configure additional PPPoE subinterfaces by completing Steps 6 through 11 using unique numbering.
    host1(config-subif)#interface atm 0/1.20.2

pppoe max-session-vsa

- Use to override the current PPPoE maximum session value set with the pppoe sessions command with the PPPoE maximum session value returned by the RADIUS server in the Max-Clients-Per-Interface VSA [26-143].
- RADIUS returns the Max-Clients-Per-Interface VSA value in Access-Accept messages for each subscriber during PPP authentication.
- By default, the router ignores the PPPoE maximum session value returned by RADIUS.
- The router never overrides the maximum number of PPPoE subinterfaces supported per line module with a value from RADIUS that is either 0 (zero) or greater than the maximum number of supported PPPoE subinterfaces. For example, if the maximum number of PPPoE subinterfaces supported for a particular line module is 8000 and the PPPoE maximum session value returned by RADIUS is 0 (zero) or greater than 8000, the RADIUS value in this case is ignored.

  See JunosE Release Notes, Appendix A, System Maximums corresponding to your software release for information about the maximum number of PPPoE subinterfaces supported for each line module.

- The following rules apply if you configure the router to override the current PPPoE maximum session value for the interface with the PPPoE maximum session value returned by RADIUS in the Max-Clients-Per-Interface VSA:

  - If the current PPPoE maximum session value is less than the PPPoE maximum session value returned by RADIUS, the PPPoE application overrides the current maximum session value with the value returned by RADIUS and proceeds with creation of the PPPoE interface.
  - If the current number of active PPPoE sessions, including the current session, is greater than the PPPoE maximum session value returned by RADIUS, PPPoE ignores (drops) the new session.
  - If the current number of active PPPoE sessions is less than or equal to the PPPoE maximum session value returned by RADIUS, PPPoE proceeds with creation of the PPPoE interface.
  The following table shows examples of the PPPoE maximum session value when a new subscriber logs in, and indicates the status of the current session.

  PPPoE Maximum Session Value from RADIUS | Current PPPoE Maximum Session Value | Existing Number of PPPoE Sessions | New PPPoE Maximum Session Value | New Number of PPPoE Sessions | Status of Session
  --- | --- | --- | --- | --- | ---
  10 | 5 | 4 | 10 | 5 | PPP session up
  3 | 5 | 4 | 3 | 5 | PPP/PPPoE session down
  5 | 5 | 4 | 5 | 5 | PPP session up

- Example
  host1(config-if)#pppoe max-session-vsa override
- Use the no version to restore the default behavior, ignore.
- See pppoe max-session-vsa.

Figure 38 illustrates the interface stack for this configuration.

Figure 38: Example of PPPoE over ATM Stacking

atm pvc

- Use to configure a PVC on an ATM interface.
- The following parameters are mandatory:
  - vcd —Virtual circuit descriptor, which identifies a virtual circuit in the range 1–2147483647. The vcd is a unique number that you assign, which identifies a virtual circuit. The vcd value has no relationship to the vpi and vci values and has meaning only to the E Series router.
  - vpi—Virtual path identifier of the PVC. The VPI is an 8-bit field in the ATM cell header. The VPI value is unique on a single link, not throughout the ATM network, because it has meaning only to the E Series router. The VPI value must match the value on the switch. The parameters vpi and vci cannot be both set to 0; if one is 0, the other cannot be 0.
  - vci —Virtual channel identifier. The VCI is a 16-bit field in the ATM cell header. The VCI value is unique on a single link, not throughout the ATM network, because it has meaning only to the E Series router. The parameters vpi and vci cannot be both set to 0; if one is 0, the other cannot be 0.
  - encapsulation type:
    - aal5snap—Specifies a logical link control (LLC) encapsulated circuit. An LLC/Subnetwork Access Protocol (LLC/SNAP) header precedes the protocol datagram.
    - aal5mux ip—Specifies a multiplexed circuit used for IP only.
    - aal5autoconfig—Enables the autodetection of a 1483 encapsulation (LLC/SNAP or VC multiplexed).
- Example
  host1(config-if)#atm pvc 10 100 22 aal5autoconfig
- Use the no version to remove the specified PVC.
- See atm pvc.

encapsulation ppp

- Use to specify PPP as the encapsulation method for the interface.
- Example
  host1(config-subif)#encapsulation ppp
- Use the no version to disable PPP on an interface.
- See encapsulation ppp.

encapsulation pppoe

- Use to specify PPPoE as the encapsulation method for the interface.
- Example
  host1(config-subif)#encapsulation pppoe
- Use the no version to disable PPPoE on an interface.
- See encapsulation pppoe.

interface atm

- Use to configure an ATM interface.
- To specify an ATM interface for ERX7xx models, ERX14xx models, and ERX310 router, use the slot/port.[subinterface ] format.
  - slot—Number of the chassis slot
  - port—Port number on the I/O module
  - subinterface—Number of the subinterface in the range 1–2147483647
- To specify an ATM interface for E120 and E320 routers, use the slot/adapter/port[.subinterface ] format.
  - slot—Number of the chassis slot
  - adapter—Identifier for the IOA within the E320 chassis, either 0 or 1, where:
    - 0 indicates that the IOA is installed in the right IOA bay (E120 router) or the upper IOA bay (E320 router).
    - 1 indicates that the IOA is installed in the left IOA bay (E120 router) or the lower IOA bay (E320 router).
  - port—Port number on the IOA
  - subinterface—Number of the subinterface in the range 1–2147483647
- For more information, see Creating a Basic Configuration in Configuring ATM .
- Examples
  host1(config)#interface atm 0/1.19 host1(config)#interface atm 0/0/1.19
- Use the no version to remove the interface or subinterface.
- See interface atm.

ip address

- Use to assign an IP address and subnet mask to a subinterface.
- Example
  host1(config-if)#ip address 192.1.1.1 255.255.255.0
- Use the no version to remove an IP address or disable IP processing.
- See ip address.

pppoe acName

- Use to configure an access concentrator (AC) name on the PPPoE interface. When the AC (the server) receives a PPPoE Active Discovery Initiation (PADI) packet that it can serve, it replies by sending a PPPoE Active Discovery Offer (PADO) packet. The PADO packet contains the AC name configured using this command.
- If the AC name is not configured, the router name is used.
- The AC name can be a maximum of 64 characters.
- Example
  host1(config-subif)#pppoe acName CYM9876
- Use the no version to remove the AC name.
- See pppoe acName.

pppoe duplicate-protection

- Use to prevent a client from establishing more than one session using the same MAC address.
- This feature is disabled by default.
- For PPPoE sessions that contain the IWF-Session DSL Forum VSA (26-254) in the PADR packets sent from the client to the PPPoE access concentrator, multiple subscriber sessions with the same MAC address can originate. This behavior occurs because the interworking functionality (IWF) causes a PPPoE over ATM or PPP over ATM (PPPoA) session to be converted by the digital subscriber line access multiplexer (DSLAM) into a PPPoE session. As a result of this conversion, the MAC addresses of all IWF PPPoE sessions contain the MAC address of the DSLAM device.

  For PPPoE sessions with the IWF-Session VSA, duplication of MAC addresses is permitted by default. Regardless of whether the duplicate protection feature is enabled, multiple IWF PPPoE sessions with the same MAC address (the address of the DSLAM device) are not terminated until the limit on the maximum number of PPPoE sessions configured on the major interface is reached.

  See Guidelines for Configuring Duplicate Protection for IWF PPPoE Sessions for a list of considerations to be observed when you use the duplicate protection feature for IWF PPPoE sessions.

- Example
  host1(config-subif)#pppoe duplicate-protection
- Use the no version to disable duplicate protection.
- See pppoe duplicate-protection.

pppoe mtu

- Use to set the MTU using a combination of lower layer restrictions and controls.
- You can specify an MTU greater than the current maximum permitted by RFC 2516, in the range 66–65535.
- You can use the use-lower-layer keyword to use the lower layer interface value minus any PPPoE overhead. You can use the use-mtu-tag keyword to use the provided PPPoE mtu tag value.
- Example
  host1(config-profile)#pppoe mtu 1380
- Use the no version to restore the default value, 1494.
- See pppoe mtu.

pppoe sessions

- Use to specify the maximum number of PPPoE subinterfaces permitted on an interface, in the range 1–8000 (ERX routers) or 1–32,000 (E120 and E320 router). On the ES2 10G ADV LM (E120 and E320 router), you can have PPPoE subinterfaces in the range 1–32000. The default value is 8000 (ERX routers) or 16,000 (E120 and E320 router) or 32,000 (ES2 10G ADV LM).

- The pppoe sessions command affects only those subinterfaces that you create after issuing this command. Previously created interfaces remain, even if their number exceeds the new value for pppoe sessions.

  | Note: The number of subinterfaces permitted on the interface for E120 and E320 routers is in the range 1–32,000 irrespective of the type of line module. However, if you specify a value greater than the number of subinterfaces supported by a line module, the number of subinterfaces created is the default maximum value for that line module. For example, if you specify the number of subinterfaces for the ES2 4G LM as 32,000 interfaces, the number of subinterfaces created is 16,000 which is the default maximum value for the ES2 4G LM.

- Example
  host1(config-if)#pppoe sessions 128
- Use the no version to restore the default value, 8000 (ERX routers) or 16,000 (E120 and E320 routers) or 32,000 (ES2 10G ADV LM).
- See pppoe sessions.