PPPoE over VLAN Enhancements Configuration Limit Removal and ATM Support

The PPPoE over VLAN Enhancements: Configuration Limit Removal and ATM Support feature removes the requirement for each PPPoE VLAN to be created on a subinterface. Allowing more than one PPPoE VLAN to be configured on a main interface increases the number of VLANs that can be configured on a router to 4000 VLANs per interface.

Individual VLANs or a range of VLANs can be configured on an interface. You can configure a VLAN range on a main interface and at the same time configure VLANs outside the range on subinterfaces of the same interface.

The PPPoE over VLAN Enhancements: Configuration Limit Removal and ATM Support feature enables ATM PVCs to process PPPoE over VLAN packets that use bridged RFC 1483 encapsulation. This capability allows PPPoE traffic from different IEEE 802.1Q VLANs to be multiplexed over the same ATM PVC.

The figure below shows a sample network topology that implements PPPoE over VLAN on ATM PVCs. In this topology, a service provider is using an Ethernet switch to provide Ethernet service to home users and a single PVC to provide the switch with WAN access. The home users use PPPoE to access services on the network access server (NAS). Each port on the switch is assigned a separate VLAN, and the VLANs are trunked over a Fast Ethernet or Gigabit Ethernet interface that is connected to a digital subscriber line (DSL) modem acting as a bridge.

The IEEE 802.1Q VLAN-encapsulated traffic coming in from the Ethernet switch trunk is encapsulated in RFC 1483 bridged encapsulation by the DSL modem and sent across the ATM WAN to the NAS. The NAS, which is configured to support PPPoE over VLANs over ATM PVCs, will extract the PPPoE packet from the PPPoE over IEEE 802.1Q VLAN over RFC 1483 bridged encapsulation and provide PPPoE services to the user.

In the downlink, the NAS sends packets in PPPoE over IEEE 802.1Q VLAN over RFC 1483 bridged encapsulation. The DSL modem strips off the RFC 1483 encapsulation and forwards the IEEE 802.1Q VLAN packets across the trunk to the switch. The switch then sends the Ethernet packets to the port associated with the IEEE 802.1 VLAN ID.

Figure 1

Sample Network Topology for PPPoE over IEEE 802.1Q VLANs over ATM

The PPPoE over VLAN Enhancements: Configuration Limit Removal and ATM Support feature has the following benefits:

• Increases the number of VLANs that can be configured on a router to 4000 VLANs per interface by removing the requirement for each PPPoE VLAN to be configured on a subinterface.
• Provides support for PPPoE over VLANs over ATM interfaces using RFC 1483 bridged encapsulation

1.    enable

2.    configure terminal

3.    interface type number

4.   Do one of the following:

5.    pppoe enable [group group-name]

1.    enable

2.    configure terminal

3.    interface atm number . subinterface-number {multipoint | point-to-point}

4.    pvc [name] vpi / vci

5.    protocol pppovlan dot1q {vlan-id | start-vlan-id end-vlan-id} [group group-name]

1.    enable

2.    configure terminal

3.    vc-class atm name

4.    protocol pppovlan dot1q {vlan-id | start-vlan-id end-vlan-id} [group group-name]

1.    enable

2.    clear pppoe {interface type number [vc {[vpi/]vci | vc-name}] [vlan vlan-id] | rmac mac-address [sid session-id] | all}

3.    debug pppoe {data | errors | events | packets} [rmac remote-mac-address | interface type number[vc {[vpi /]vci | vc-name}] [vlan vlan-id]]

The following example shows how to configure PPPoE over a range of IEEE 802.1Q VLANs on Fast Ethernet interface 0/0. The VLAN range is configured on the main interface and therefore each VLAN will not use up a separate subinterface.

bba-group pppoe PPPOE 
 virtual-template 1 
 sessions per-mac limit 1 
interface virtual-template 1 
 ip address 10.10.10.10 255.255.255.0 
 mtu 1492 
interface fastethernet 0/0
 no ip address 
 no ip mroute-cache 
 duplex half 
 vlan-range dot1q 20 30 
  pppoe enable group PPPOE 
  exit-vlan-config 

The following example shows how to configure an ATM PVC to support PPPoE over a range of IEEE 802.1Q VLANs:

bba-group pppoe PPPOEOA
 virtual-template 1 
 sessions per-mac limit 1 
interface virtual-template 1 
 ip address 10.10.10.10 255.255.255.0 
 mtu 1492 
interface atm 4/0.10 multipoint 
 pvc 10/100 
  protocol pppovlan dot1q range 10 30 group PPPOEOA