Table Of Contents

Configuring Broadband Access:
PPP and Routed Bridge Encapsulation

Configuring PPP over ATM

PPP over ATM Configuration Task List

Creating and Configuring a Virtual Template

Configuring IETF-Compliant MUX Encapsulated PPP over ATM PVCs

Configuring IETF-Compliant LLC Encapsulated PPP over ATM PVCs

Configuring Cisco-Proprietary PPP over ATM PVCs

Configuring PPP over ATM SVCs

Configuring PPPoE over ATM

PPPoE Stage Protocols

PPPoE over ATM Conditions and Restrictions

PPPoE over ATM Configuration Task List

Configuring a Virtual Template

Configuring a VPDN Group for PPPoE over ATM

Enabling PPPoE on an ATM PVC or PVC Range

Configuring PPPoE over Ethernet

PPPoE over Ethernet Configuration Task List

Configuring a Virtual Template

Enabling PPPoE on an Ethernet Interface

Configuring PPPoE in a VPDN Group

Verifying PPPoE over Ethernet

Configuring PPPoE over IEEE 802.1Q VLANs

PPPoE over IEEE 802.1Q VLANs Conditions and Restrictions

PPPoE over IEEE 802.1Q VLANs Configuration Task List

Configuring a Virtual Template

Enabling PPPoE on an Ethernet 802.1Q Interface

Configuring PPPoE in a VPDN Group for an 802.1Q VLAN

Verifying PPPoE over an IEEE 802.1Q VLAN

Configuring RADIUS Port Identification for PPP

PPP over ATM and PPPoE over ATM Format

PPPoE over IEEE 802.1Q VLANs Format

RADIUS Port Identification for PPP Configuration Tasks

Configuring the LAC for RADIUS Port Identification for PPP

Configuring the LNS for RADIUS Port Identification for PPP

Configuring ATM Routed Bridge Encapsulation

ATM RBE Subinterface Grouping by PVC Range

ATM Routed Bridge Encapsulation Configuration Task List

Configuring ATM Routed Bridge Encapsulation

Verifying ATM Routed Bridge Encapsulation

Configuring an ATM PVC Range

Creating an ATM PVC Range

Deactivating a PVC Range

Configuring an Individual PVC Within a PVC Range

Deactivating an Individual PVC Within a PVC Range

Verifying an ATM PVC Range

Configuration Examples

PPP over ATM Configuration Examples

IETF-Compliant MUX Encapsulated PPP over ATM Configuration Examples

IETF-Compliant LLC Encapsulated PPP over ATM Configuration Examples

Cisco Proprietary PPP-over-ATM Example

PPP over an ATM SVC Configuration Example

PPPoE over ATM Configuration Example

PPPoE over Ethernet Configuration Example

PPPoE over an IEEE 802.1Q VLAN Configuration Example

RADIUS Port Identification for PPP Configuration Examples

RADIUS Port Identification for PPPoE over ATM Example

RADIUS Port Identification for PPPoE over an 802.1Q VLAN Example

Configuring the LNS for RADIUS Port Identification for PPP Example

ATM Routed Bridge Encapsulation Configuration Examples

ATM Routed Bridge Encapsulation Example

ATM Routed Bridge Encapsulation on an Unnumbered Interface Example

Concurrent Bridging and ATM Routed Bridge Encapsulation Example

ATM PVC Range Configuration Examples

ATM PVC Range on a Point-to-Point Subinterface Example

ATM PVC Range on a Multipoint Subinterface Example

Individual PVC Within a PVC Range Configuration Example

Configuring Broadband Access:
PPP and Routed Bridge Encapsulation

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This chapter describes how to configure a central office aggregator for broadband access using PPP or ATM routed bridge encapsulation.

This chapter includes the following sections:

•Configuring PPP over ATM

•Configuring PPPoE over ATM

•Configuring PPPoE over Ethernet

•Configuring PPPoE over IEEE 802.1Q VLANs

•Configuring RADIUS Port Identification for PPP

•Configuring ATM Routed Bridge Encapsulation

•Configuring an ATM PVC Range

•Configuration Examples

For further general information about broadband access using PPP or ATM routed bridge encapsulation, see the "Wide-Area Networking Overview" chapter at the beginning of this book.

For a complete description of the commands in this chapter that are specific to broadband access configuration, refer to the chapter "Broadband Access: PPP and Routed Bridge Encapsulation Commands" in the Cisco IOS Wide-Area Networking Command Reference. To locate documentation of other commands that appear in this chapter, use the command reference master index or search online.

To identify the hardware platform or software image information associated with a feature, use the Feature Navigator on Cisco.com to search for information about the feature or refer to the software release notes for a specific release. For more information, see the section "Identifying Supported Platforms" in the chapter "Using Cisco IOS Software."

Configuring PPP over ATM

PPP over ATM can be configured on all platforms running Cisco IOS Release 12.1 or later, except for IETF-compliant LLC encapsulated PPP over ATM, which is not available for the Cisco MC3810 series platform.

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Note All forms of PPP over ATM are now supported on the ATM port adapters, except for the PA-A1 ATM port adapter for Cisco IOS Release 12.1. All forms of PPP over ATM are now supported on the enhanced ATM port adapter for Cisco IOS Release 12.1 or later.

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Figure 10 shows a typical scenario for using Cisco-proprietary PPP over ATM.

Figure 10 PPP-over-ATM Network Environment

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Note If you need to configure the Cisco MGX 8220 shelf for frame forwarding at the remote sites, refer to the Cisco MGX 8220 Command Supplement for command line instructions or the Cisco StrataView Plus Operations Guide for StrataView Plus instructions. If you configure the MGX using the command line interface, use the addport and addchan commands and select frame forwarding for the port_type and chan_type arguments, respectively.

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When you configure PPP over ATM, a logical interface known as a virtual access interface associates each PPP connection with an ATM VC. You can create this logical interface by configuring an ATM PVC or SVC. This configuration encapsulates each PPP connection in a separate PVC or SVC, allowing each PPP connection to terminate at the router ATM interface as if received from a typical PPP serial interface.

The virtual access interface for each VC obtains its configuration from a virtual interface template (virtual template) when the VC is created. Before you create the ATM VC, it is recommended that you create and configure a virtual template as described in the secrtion "Creating and Configuring a Virtual Template," next.

Once you have configured the router for PPP over ATM, the PPP subsystem starts and the router attempts to send a PPP configure request to the remote peer. If the peer does not respond, the router periodically goes into a "listen" state and waits for a configuration request from the peer. After a timeout (typically 45 seconds), the router again attempts to reach the remote router by sending configuration requests.

The virtual access interface remains associated with a VC as long as the VC is configured. If you deconfigure the VC, the virtual access interface is marked as deleted. If you shut down the associated ATM interface, you will also cause the virtual access interface to be marked as down (within 10 seconds), and you will bring the PPP connection down. If you set a keepalive timer of the virtual template on the interface, the virtual access interface uses the PPP echo mechanism to verify the existence of the remote peer.

The following three types of PPP over ATM connections are supported:

•IETF-compliant MUX encapsulated PPP over ATM

•IETF-compliant LLC encapsulated PPP over ATM

•Cisco-proprietary PPP over ATM

PPP over ATM Configuration Task List

To configure PPP over ATM, complete the tasks described in the following sections. Each task is identified as optional or required:

•Creating and Configuring a Virtual Template (Optional, but recommended)

•Configuring IETF-Compliant MUX Encapsulated PPP over ATM PVCs (Optional)

•Configuring IETF-Compliant LLC Encapsulated PPP over ATM PVCs (Optional)

•Configuring Cisco-Proprietary PPP over ATM PVCs (Optional)

•Configuring PPP over ATM SVCs (Optional)

Creating and Configuring a Virtual Template

Prior to configuring the ATM PVC for PPP over ATM, you typically create and configure a virtual template. To create and configure a virtual template, use the following commands beginning in global configuration mode:

	Command	Purpose
Step 1	Router(config)# interface virtual-template number	Creates a virtual template, and enter interface configuration mode.
Step 2	Router(config-if)# encapsulation ppp	Enables PPP encapsulation on the virtual template.
Step 3	Router(config-if)# ip unnumbered ethernet number	(Optional) Enables IP without assigning a specific IP address on the LAN.

Other optional configuration commands can be added to the virtual template configuration. For example, you can enable the PPP authentication on the virtual template using the ppp authentication chap command. Refer to the "Configuring Virtual Template Interfaces" chapter in the Cisco IOS Dial Technologies Configuration Guide for additional information about configuring the virtual template.

All PPP parameters are managed within the virtual template configuration. Configuration changes made to the virtual template are automatically propagated to the individual virtual access interfaces. Multiple virtual access interfaces can originate from a single virtual template; therefore, multiple PVCs can use a single virtual template.

Cisco IOS software supports up to 25 virtual template configurations. If greater numbers of tailored configurations are required, an authentication, authorization, and accounting (AAA) server may be employed. Refer to the "Configuring Per-User Configuration" chapter in the Cisco IOS Dial Technologies Configuration Guide for additional information on configuring an AAA server.

If the parameters of the virtual template are not explicitly defined before the ATM PVC is configured, the PPP interface is brought up using default values from the virtual template identified. Some parameters (such as an IP address) take effect only if specified before the PPP interface comes up. Therefore, it is recommended that you explicitly create and configure the virtual template before configuring the ATM PVC to ensure that such parameters take effect. Alternatively, if parameters are specified after the ATM PVC has already been configured, use the shutdown command followed by a no shutdown command on the ATM subinterface to restart the interface; this restart will cause the newly configured parameters (such as an IP address) to take effect.

Network addresses for the PPP-over-ATM connections are not configured on the main ATM interface or subinterface. Instead, these are configured on the appropriate virtual template or obtained via AAA.

The virtual templates support all standard PPP configuration commands; however, not all configurations are supported by the PPP-over-ATM virtual access interfaces. These restrictions are enforced at the time the virtual template configuration is applied (cloned) to the virtual access interface. These restrictions are described in the following paragraphs.

Only standard FIFO queuing is supported when applied to PPP-over-ATM virtual access interfaces. Other types of queuing which are typically configured on the main interface are not (for example, fair queuing). If configured, these configuration lines are ignored when applied to a PPP-over-ATM interface.

Although fast switching is supported, flow and optimum switching are not; these configurations are ignored on the PPP-over-ATM virtual access interface. Fast switching is enabled by default for the virtual template configuration. If fast switching is not desired, use the no ip route-cache command to disable it.

The PPP reliable link that uses Link Access Procedure, Balanced (LAPB) is not supported.

Because an ATM PVC or SVC is configured for this feature, the following standard PPP features are not applicable and should not be configured:

•Asynchronous interfaces

•Dialup connections

•Callback on PPP

Configuring IETF-Compliant MUX Encapsulated PPP over ATM PVCs

IETF-compliant MUX encapsulated PPP over ATM, also known as null encapsulation, allows you to configure PPP over ATM using a virtual circuit (VC) multiplexed encapsulation mode. This feature complies with IETF RF 2364 entitled PPP over AAL5.

You can configure ATM PVCs for IETF-compliant MUX encapsulated PPP over ATM on either point-to-point or multipoint subinterfaces. Multiple PVCs on multipoint subinterfaces significantly increase the maximum number of PPP-over-ATM sessions running on a router.

To configure a PVC with IETF-compliant MUX PPP over ATM that supports VC multiplexed PPP payloads, use the following commands starting in global configuration mode:

	Command	Purpose
Step 1	Router(config)# interface atm slot/port.subinterface-number point-to-point or Router(config)# interface atm number.subinterface-number point-to-point or Router(config)# interface atm slot/port.subinterface-number multipoint or Router(config)# interface atm number.subinterface-number multipoint	Specifies an ATM point-to-point or multipoint subinterface using the appropriate format of the interface atm command.1
Step 2	Router(config-subif)# pvc [name] vpi/vci	Configures the PVC.
Step 3	Router(config-if-atm-vc)# encapsulation aal5mux ppp virtual-template number	Configures VC multiplexed encapsulation on a PVC.

1 To determine the correct form of the interface atm command, consult your ATM network module, port adapter, or router documentation.

To configure a PVC range with IETF-compliant MUX PPP over ATM that supports VC multiplexed PPP payloads, use the following commands beginning in global configuration mode:

	Command	Purpose
Step 1	Router(config)# interface atm slot/port.subinterface-number point-to-point or Router(config)# interface atm number.subinterface-number point-to-point or Router(config)# interface atm slot/port.subinterface-number multipoint or Router(config)# interface atm number.subinterface-number multipoint	Specifies an ATM point-to-point or multipoint subinterface using the appropriate format of the interface atm command.1
Step 2	Router(config-subif)# range [range-name] pvc start-vpi/start-vci end-vpi/end-vci	Creates a range of PVCs.
Step 3	Router(config-if-atm-range)# encapsulation aal5mux ppp virtual-template number	Configures VC multiplexed encapsulation on a PVC range.

1 To determine the correct form of the interface atm command, consult your ATM network module, port adapter, or router documentation.

IETF-Compliant PPP over ATM is not supported on ATM SVCs and can only be applied to PVCs.

The IETF-Compliant PPP over ATM feature was designed to support installations with ADSL circuits. For an example of using ADSL termination, see the section "ADSL Termination Example" under "PPP over ATM Configuration Examples" at the end of this chapter.

Configuring IETF-Compliant LLC Encapsulated PPP over ATM PVCs

IETF-compliant LLC encapsulated PPP over ATM LLC Encapsulation allows you to configure PPP over ATM with LLC encapsulation. It accommodates Frame Relay-to-ATM service interworking (Frame Relay forum standard FRF.8). There is no equivalent VC multiplexed encapsulation mode for Frame Relay; therefore, LLC encapsulation is required for Frame Relay-to-ATM networking. This version of PPP over ATM also enables you to carry multiprotocol traffic. For example, a VC will carry both PPP and IPX traffic.

Figure 11 illustrates Frame Relay-to-ATM interworking.

Figure 11 Frame Relay-to-ATM Interworking

You can configure ATM PVCs for IETF-compliant LLC encapsulated PPP over ATM on either point-to-point or multipoint subinterfaces. Multiple PVCs on multipoint subinterfaces significantly increase the maximum number of PPP-over-ATM sessions running on a router.

To configure IETF-compliant LLC encapsulated PPP over ATM on a PVC, use the following commands beginning in global configuration mode:

	Command	Purpose
Step 1	Router(config)# interface atm slot/port.subinterface-number point-to-point or Router(config)# interface atm number.subinterface-number point-to-point or Router(config)# interface atm slot/port.subinterface-number multipoint or Router(config)# interface atm number.subinterface-number multipoint	Specifies an ATM point-to-point or multipoint subinterface using the appropriate format of the interface atm command.1
Step 2	Router(config-subif)# pvc [name] vpi/vci	Configures the PVC.
Step 3	Router(config-if-atm-vc)# encapsulation aal5snap2	Configures LLC SNAP encapsulation on the PVC.
Step 4	Router(config-if-atm-vc)# protocol ppp virtual-template number	Configures IETF PPP over ATM LLC Encapsulation on the PVC.

1 To determine the correct form of the interface atm command, consult your ATM network module, port adapter, or router documentation. 2 The snap encapsulation is a misnomer here, since this encapsulation configures both LLC and SNAP encapsulation on the VC. If snap encapsulation is not configured at a lower inheritance level, or another type of encapsulation is configured at a lower inheritance level, you will have to configure both snap and the protocol ppp command to ensure that PPP over ATM with LLC encapsulation is configured on your VC.

To configure IETF-compliant LLC encapsulated PPP over ATM on a PVC range, use the following commands beginning in global configuration mode:

	Command	Purpose
Step 1	Router(config)# interface atm slot/port.subinterface-number point-to-point or Router(config)# interface atm number.subinterface-number point-to-point or Router(config)# interface atm slot/port.subinterface-number multipoint or Router(config)# interface atm number.subinterface-number multipoint	Specifies an ATM point-to-point or multipoint subinterface using the appropriate format of the interface atm command.1
Step 2	Router(config-subif)# range [range-name] pvc start-vpi/start-vci end-vpi/end-vci	Creates a range of PVCs.
Step 3	Router(config-if-atm-range)# encapsulation aal5snap2	Configures LLC SNAP encapsulation on the PVC range.
Step 4	Router(config-if-atm-range)# protocol ppp virtual-template number	Configures IETF PPP over ATM LLC Encapsulation on the PVC. range

1 To determine the correct form of the interface atm command, consult your ATM network module, port adapter, or router documentation. 2 The snap encapsulation is a misnomer here, since this encapsulation configures both LLC and SNAP encapsulation on the VC. If snap encapsulation is not configured at a lower inheritance level, or another type of encapsulation is configured at a lower inheritance level, you will have to configure both snap and the protocol ppp command to ensure that PPP over ATM with LLC encapsulation is configured on your VC.

For more information about configuring an ATM PVC range, see the section "Configuring an ATM PVC Range" later in this chapter.

You can also configure IETF-compliant LLC encapsulated PPP over ATM in a VC class and apply this VC class to an ATM VC, subinterface, or interface. For information about configuring a VC class, refer to the section "Configuring VC Classes" in the chapter "Configuring ATM."

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Note Depending on whether you configure IETF-compliant LLC encapsulated PPP over ATM directly on a PVC or interface, your PVC will inherit the configuration that takes highest precedence. For a description of the inheritance hierarchy, see the protocol command in the Cisco IOS Wide-Area Networking Command Reference Guide.

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Configuring Cisco-Proprietary PPP over ATM PVCs

You can configure ATM PVCs for Cisco proprietary PPP over ATM on either point-to-point or multipoint subinterfaces. Multiple PVCs on multiple subinterfaces significantly increases the maximum number of PPP-over-ATM sessions running on a router. Remote branch offices must have Cisco proprietary PPP over ATM configured on PPP-compatible devices interconnecting directly to Cisco's ATM Switch Interface Shelf (AXIS) equipment through a leased-line connection. The shelves provide frame forwarding encapsulation and are terminated on BPX cores prior to connecting to a Cisco 7500 series router.

To configure Cisco proprietary PPP over ATM on a PVC, use the following commands starting in global configuration mode:

	Command	Purpose
Step 1	Router(config)# interface atm slot/port.subinterface-number point-to-point or Router(config)# interface atm number.subinterface-number point-to-point or Router(config)# interface atm slot/port.subinterface-number multipoint or Router(config)# interface atm number.subinterface-number multipoint	Specifies an ATM point-to-point or multipoint subinterface using the appropriate format of the interface atm command.1
Step 2	Router(config-subif)# pvc [name] vpi/vci	Configures the PVC.
Step 3	Router(config-if-atm-vc)# encapsulation aal5ciscoppp virtual-template number	Configures Cisco Proprietary PPP over ATM encapsulation on the PVC.

1 To determine the correct form of the interface atm command, consult your ATM network module, port adapter, or router documentation.

To configure Cisco proprietary PPP over ATM on a PVC range, use the following commands beginning in global configuration mode:

	Command	Purpose
Step 1	Router(config)# interface atm slot/port.subinterface-number point-to-point or Router(config)# interface atm number.subinterface-number point-to-point or Router(config)# interface atm slot/port.subinterface-number multipoint or Router(config)# interface atm number.subinterface-number multipoint	Specifies an ATM point-to-point or multipoint subinterface using the appropriate format of the interface atm command.1
Step 2	Router(config-subif)# range [range-name] pvc start-vpi/start-vci end-vpi/end-vci	Configures the PVC range.
Step 3	Router(config-if-atm-range)# encapsulation aal5ciscoppp virtual-template number	Configures Cisco-Proprietary PPP over ATM encapsulation on the PVC range.

1 To determine the correct form of the interface atm command, consult your ATM network module, port adapter, or router documentation.

For more information about configuring an ATM PVC range, see the section "Configuring an ATM PVC Range" later in this chapter.

For an example of configuring Cisco proprietary PPP over ATM, see the section "Configuring Cisco-Proprietary PPP over ATM PVCs" at the end of this chapter.

Configuring PPP over ATM SVCs

When PPP over ATM is configured over an SVC rather than a PVC, each time an end user initiates a connection to a Network Access Provider (NAP) or Network Service Provider (NSP), an ATM SVC is established using a configured ATM address. A PPP session is then established over the SVC. By using PPP, the NAPs and NSPs can authenticate users and provide suitable access to the various services being offered. Whereas PVCs require that services and destination addresses be predetermined, using PPP over ATM SVCs allows users to choose services and the quality of those services dynamically on the basis of destination address.

Figure 12 PPP over ATM SVC Terminating at an NAP

Figure 13 shows a typical network topology of PPP over ATM SVCs terminating at an NSP.

Figure 13 PPP over ATM SVC Terminating at an NSP

To configure PPP over an ATM SVC, perform the tasks in the following sections. Each task in the list is identified as optional or required.

•Configuring PPP over an ATM SVC (Required)

•Setting the ATM NSAP Address (Required)

•Verifying PPP over ATM SVCs (Optional)

Configuring PPP over an ATM SVC

To configure PPP over an ATM SVC, use the following commands beginning in global configuration mode:

	Command	Purpose
Step 1	Router(config)# interface atm slot/0 or Router(config)# interface atm slot/port-adaptor/0 or Router(config)# interface atm number or Router(config)# interface atm slot/port	Specifies an ATM interface and enters interface configuration mode. To determine the correct form of the interface atm command, consult your ATM network module, port adapter, or router documentation.
Step 2	Router(config-if)# svc [name]	Creates an ATM SVC.
Step 3	Router(config-if-atm-vc)# encapsulation aal5auto	Specifies encapsulation auto, which allows the SVC to use either aal5snap or aal5mux encapsulation types.
Step 4	Router(config-if-atm-vc)# protocol ppp virtual-template number	Specifies that PPP is established over the ATM SVC using the configuration from the specified virtual template.
Step 5	Router(config-if-atm-vc)# max vc number	Specifies the maximum number of SVCs that can be established using the current configuration.
Step 6	Router(config-if-atm-vc)# max bandwidth kbps	Specifies the total amount of bandwidth available to all SVCs in the current configuration.

Setting the ATM NSAP Address

To set the network service access point (NSAP) address for the ATM interface, use the following command in interface configuration mode:

Command	Purpose
Router(config-if)# atm nsap-address nsap-address	Sets the NSAP address for an ATM interface.

When configuring an SVC, you must use the atm nsap-address command to define the source NSAP address. It identifies a particular port on the ATM network and must be unique across the network.

Verifying PPP over ATM SVCs

To verify the configuration of PPP over ATM SVCs, use the following privileged EXEC command:

Command	Purpose
Router# show atm svc	Display sall ATM SVCs and traffic information.
Router# show atm svc ppp	Displays information about each SVC configured for PPP over ATM.

Configuring PPPoE over ATM

PPPoE over ATM provides the ability to connect a network of hosts over a simple bridging-access device to a remote access concentrator. With this model, each host utilizes its own PPPoE stack and the user is presented with a familiar user interface. Access control, billing, and type of service can be configured on a per-user, rather than a per-site, basis. Before a point-to-point connection over Ethernet can be provided, each PPP session must learn the Ethernet address of the remote peer and establish a unique session identifier. A unique session identifier is provided by the PPPoE Discovery Stage protocol.

Figure 14 shows a sample network topology using PPPoE over ATM.

Figure 14 PPPoE over ATM Sample Network Topology

PPPoE Stage Protocols

PPPoE has two distinct stage protocols. The stage protocols are listed and summarized in Table 6.

Table 6 PPPoE Stage Protocols

Stage Protocols	Description
Discovery Stage protocol	Remains stateless until a PPPoE session is established. Once the PPPoE session is established, both the host and the access concentrator must allocate the resources for a PPP virtual access interface.
PPP Session Stage protocol	Once the PPPoE session is established, sends PPPoE data as in any other PPP encapsulation.

There are four steps to the Discovery Stage:

1. Host broadcasts a PPPoE Active Discovery Initiation (PADI) packet.

2. When the access concentrator receives a PADI that it can serve, it replies by sending a PPPoE Active Discovery Offer (PADO) packet to the host.

3. Because the PADI was broadcast, the host may receive more than one PADO packet. The host looks through the PADO packets it receives and chooses one. The choice can be based on the AC name or the services offered. The host then sends a single PPPoE Active Discovery Request (PADR) packet to the access concentrator that it has chosen.

4. When the access concentrator receives a PADR packet, it prepares to begin a PPP session. It generates a unique session ID for the PPPoE session and replies to the host with a PPPoE Active Discovery Session-confirmation (PADS) packet.

When a host wishes to initiate a PPPoE session, it must first perform discovery to identify the Ethernet MAC address of the peer and establish a PPPoE session ID. Although PPP defines a peer-to-peer relationship, discovery is inherently a client/server relationship. In the discovery process, a host (the client) discovers an access concentrator (the server). Depending on the network topology, there may be more than one access concentrator with which the host can communicate. The Discovery Stage allows the host to discover all access concentrators and then select one. When discovery is completed, both the host and the selected access concentrator have the information they will use to build their point-to-point connection over Ethernet.

PPPoE over ATM Conditions and Restrictions

Note the following conditions and restrictions for PPPoE over ATM:

•PPPoE will not be supported on any other LAN interfaces, such as FDDI and Token Ring.

•Fast switching is supported. PPPoE over ATM forwarding information base (FIB) switching will be supported for IP. All other protocols will be switched over process switching.

•Bridging is supported on the ATM PVCs running PPPoE.

•PPPoE will be supported on ATM PVCs compliant with RFC 1483 only.

•Only dial-in mode will be supported. Dial-out mode will not be supported.

•2000 simultaneous PPP sessions are supported on the Cisco series 7200 with enhanced ATM port adapters and on the Cisco series 6400 platforms only, both with 128 MB of DRAM.

PPPoE over ATM Configuration Task List

See the following sections for configuration tasks for PPPoE over ATM. Each task in the list indicates if the task is optional or required.

•Configuring a Virtual Template (Optional, but recommended)

•Configuring a VPDN Group for PPPoE over ATM (Required)

•Enabling PPPoE on an ATM PVC or PVC Range (Required)

Configuring a Virtual Template

Prior to configuring the VPDN group and the ATM PVC for PPPoE over ATM, you typically configure a virtual template. To configure a virtual template, see the section "Creating and Configuring a Virtual Template" earlier in this chapter.

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Note Although Cisco Express Forwarding (CEF) switching is supported by PPPoE over ATM, fast switching, flow, and optimum switching are not; these configurations are ignored on the PPPoE-over-ATM virtual access interface. CEF is enabled by default for IP. All other protocol traffic will be processed switched.

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Configuring a VPDN Group for PPPoE over ATM

To configure the physical interface that will carry the PPPoE session and link it to the appropriate virtual template interface, use the following commands beginning in global configuration mode:

	Command	Purpose
Step 1	Router(config)# vpdn enable	Enables virtual private dial-up network (VPDN) configuration on this router.
Step 2	Router(config)# vpdn group name	Associates a VPDN group with a customer or VPDN profile.
Step 3	Router(config-vpdn)# accept dialin	Creates an accept dial-in VPDN group.
Step 4	Router(config-vpdn-acc-in)# protocol pppoe	Specifies the VPDN group to be used to establish PPPoE sessions.
Step 5	Router(config-vpdn-acc-in)# virtual-template template-number	Specifies which virtual template will be used to clone virtual access interfaces.
Step 6	Router(config-vpdn)# pppoe limit per-vc number	Specifies the maximum number of PPPoE sessions to be established over a VC.

Enabling PPPoE on an ATM PVC or PVC Range

To enable PPPoE on an ATM PVC, use the following commands beginning in global configuration mode:

	Command	Purpose
Step 1	Router(config)# interface atm slot/0.subinterface-number multipoint | point-to-point or Router(config)# interface atm number.subinterface-number multipoint | point-to-point	Specifies the ATM subinterface using the appropriate format of the interface atm command.1 A multipoint subinterface is recommended for interface conservation. A point-to-point subinterface will greatly restrict the total number of PPPoE sessions you can have up.
Step 1	Router(config-subif)# pvc [name] vpi/vci	Configures the PVC.
Step 2	Router(config-if-atm-vc)# encapsulation aal5snap	Specifies AAL5 SNAP for ATM encapsulation on the PVC.
Step 3	Router(config-if-atm-vc)# protocol pppoe	Specifies the protocol that the VPDN group will use.

1 Use the interface atm slot/0 command with the ATM Interface Processor (AIP) on Cisco 7500 series routers, any ATM port adapter on the Cisco 7200 series routers, and the 1-port ATM-25 network module on the Cisco 2600 and 3600 series routers. Use the interface atm slot/port-adapter/0 command with any ATM port adapter on the Cisco 7500 series routers. Use the interface atm number command with the NPM on the Cisco 4500 and 4700 routers. Use interface atm 0 on the Cisco MC3810.

To enable PPPoE on an ATM PVC range, use the following commands beginning in gobal configuration mode:

	Command	Purpose
Step 1	Router(config)# interface atm slot/0.subinterface-number multipoint | point-to-point or Router(config)# interface atm number.subinterface-number multipoint | point-to-point	Specifies the ATM subinterface using the appropriate format of the interface atm command.1 A multipoint subinterface is recommended for interface conservation. A point-to-point subinterface will greatly restrict the total number of PPPoE sessions you can have up.
Step 1	Router(config-subif)# range [range-name] pvc start-vpi/start-vci end-vpi/end-vci	Configures the PVC range.
Step 2	Router(config-if-atm-range)# encapsulation aal5snap	Specifies AAL5 SNAP for ATM encapsulation on the PVC range.
Step 3	Router(config-if-atm-range)# protocol pppoe	Specifies the VPDN group to be used for establishing PPPoE sessions on the PVC range.

1 Use the interface atm slot/0 command with the ATM Interface Processor (AIP) on Cisco 7500 series routers, any ATM port adapter on the Cisco 7200 series routers, and the 1-port ATM-25 network module on the Cisco 2600 and 3600 series routers. Use the interface atm slot/port-adapter/0 command with any ATM port adapter on the Cisco 7500 series routers. Use the interface atm number command with the NPM on the Cisco 4500 and 4700 routers. Use interface atm 0 on the Cisco MC3810.

Once you configure the router for PPPoE over ATM, the PPP subsystem starts and the router attempts to send a PPP configure request to the remote peer. If the peer does not respond, the router periodically goes into a "listen" state and waits for a configuration request from the peer. After a timeout (typically 45 seconds), the router again attempts to reach the remote router by sending configuration requests.

For more information about configuring an ATM PVC range, see the section "Configuring an ATM PVC Range" later in this chapter.

For an example of PPPoE over ATM, see the section "PPPoE over ATM Configuration Example" at the end of this chapter.

Configuring PPPoE over Ethernet

PPPoE over Ethernet enhances PPPoE functionality by adding direct connection to actual Ethernet and FastEthernet interfaces. PPPoE over Ethernet provides service-provider digital subscriber line (DSL) support by enabling multiple hosts on a shared Ethernet interface to open PPP sessions to multiple destinations with one or more bridging modems.

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Note Fast switching is supported. PPPoE FIB switching will be supported for IP. All other protocols will be switched over process switching.

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PPPoE over Ethernet Configuration Task List

To configure PPPoE on an Ethernet or FastEthernet interface, perform the tasks in the following sections. Each task is identified as required or optional.

•Configuring a Virtual Template (Optional, but recommended)

•Enabling PPPoE on an Ethernet Interface (Required)

•Configuring PPPoE in a VPDN Group (Required)

•Verifying PPPoE over Ethernet (Optional)

Configuring a Virtual Template

Prior to configuring the VPDN group and the interface for PPPoE, you typically configure a virtual template. To configure a virtual template, see the section "Creating and Configuring a Virtual Template" earlier in this chapter.

Enabling PPPoE on an Ethernet Interface

To enable PPPoE on an Ethernet interface, use the following commands beginning in global configuration mode:

	Command	Purpose
Step 1	Router(config)# interface ethernet number	Specifies an Ethernet interface, and enters interface configuration mode.
Step 2	Router(config-subif)# pppoe enable	Enables PPPoE and allows PPPoE sessions to be created through that subinterface.

Configuring PPPoE in a VPDN Group

To configure a VPDN group for PPPoE and to link it to the appropriate virtual template interface, use the following commands beginning in global configuration mode:

	Command	Purpose
Step 1	Router(config)# vpdn enable	Enables virtual private dial-up network (VPDN) configuration on this router.
Step 2	Router(config)# vpdn group name	Associates a VPDN group to a customer or VPDN profile.
Step 3	Router(config-vpdn)# accept dialin	Creates an accept dial-in VPDN group.
Step 4	Router(config-vpdn-acc-in)# protocol pppoe	Specifies the VPDN group to be used to establish PPPoE sessions.
Step 5	Router(config-vpdn-acc-in)# virtual-template template-number	Specifies which virtual template will be used to clone virtual access interfaces.
Step 6	Router(config-vpdn)# pppoe limit per-mac number	Specifies the maximum number of PPPoE sessions that can be sourced from a MAC address.

For an example of PPPoE over Ethernet, see the section "PPPoE over Ethernet Configuration Example" at the end of this chapter.

Verifying PPPoE over Ethernet

To verify PPPoE over Ethernet, use the following commands in EXEC mode:

Command	Purpose
Router# show vpdn	Displays information about active Level 2 Forwarding (L2F) Protocol tunnel and message identifiers in a VPDN.
Router# show vpdn session packet	Displays PPPoE session statistics.
Router# show vpdn session all	Displays PPPoE session information for each session ID.
Router# show vpdn tunnel	Displays PPPoE session count for the tunnel.

Configuring PPPoE over IEEE 802.1Q VLANs

IEEE 802.1Q encapsulation is used to interconnect a VLAN-capable router with another VLAN-capable networking device. When you configure PPPoE over IEEE 802.1Q VLANs, the packets on the 802.1Q link contain a standard Ethernet frame and the VLAN information associated with that frame.

PPPoE over IEEE 802.1Q VLANs Conditions and Restrictions

•The PPPoE over IEEE 802.1Q VLANs feature is supported on Fast Ethernet. The feature is also supported on 10 Mbps Ethernet when a 4e/8e AMDP2 Ethernet adapter on the Cisco 7200 series router is used.

•Only PPPoE dial-in is supported. PPPoE dial-out (client) will not be supported.

•PPPoE termination and bridging will not work together on the same VLAN.

•PPPoE will be disabled by default on a VLAN.

•The feature is supported on routers running Cisco IOS software. This feature is not supported on Route Switch Modules (RSMs) for Catalyst switches.

PPPoE over IEEE 802.1Q VLANs Configuration Task List

To configure PPPoE over an 802.1Q VLAN, perform the tasks in the following sections. Each task is identified as required or optional.

•Configuring a Virtual Template (Optional, but recommended)

•Enabling PPPoE on an Ethernet 802.1Q Interface (Required)

•Configuring PPPoE in a VPDN Group for an 802.1Q VLAN (Required)

•Verifying PPPoE over an IEEE 802.1Q VLAN (Optional)

Configuring a Virtual Template

Prior to configuring the VPDN group and the interface for PPPoE over 802.1Q VLANs, you typically configure a virtual template. To configure a virtual template, see the section "Creating and Configuring a Virtual Template" earlier in this chapter.

Enabling PPPoE on an Ethernet 802.1Q Interface

To enable PPPoE on an Ethernet 802.1Q encapsulated subinterface, use the following commands beginning in global configuration mode:

	Command	Purpose
Step 1	Router(config)# interface fastethernet slot/port.subinterface-number	Specifies a Fast Ethernet subinterface and enters subinterface configuration mode.
Step 2	Router(config-subif)# encapsulation dot1q vlan-id	Enables IEEE 802.1Q encapsulation on a specified subinterface in VLANs.
Step 3	Router(config-subif)# pppoe enable	Enables PPPoE and allows PPPoE sessions to be created through the specified subinterface.
Step 4	Router(config-subif)# pppoe max-session number	(Optional) Specifies the maximum number of PPPoE sessions under a VLAN.

Configuring PPPoE in a VPDN Group for an 802.1Q VLAN

To configure a VPDN group for PPPoE and to link it to the appropriate virtual template interface, use the following commands beginning in global configuration mode:

	Command	Purpose
Step 1	Router(config)# vpdn enable	Enables virtual private dialup network (VPDN) configuration on this router.
Step 2	Router(config)# vpdn group name	Associates a VPDN group to a customer or VPDN profile.
Step 3	Router(config-vpdn)# accept dialin	Creates an accept dial-in VPDN group.
Step 4	Router(config-vpdn-acc-in)# protocol pppoe	Specifies the VPDN group to be used to establish PPPoE sessions.
Step 5	Router(config-vpdn-acc-in)# v