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The PPPoA/PPPoE Autosense for ATM PVCs feature enables a router to distinguish between incoming PPP over ATM (PPPoA) and PPP over Ethernet (PPPoE) over ATM sessions and to create virtual access based on demand for both PPP types.
The Autosense of MUX/SNAP Encapsulation and PPPoA/PPPoE on ATM PVCs feature enhances PPPoA/PPPoE autosense functionality by providing autosense support on multiplexer (MUX) and Subnetwork Access Protocol (SNAP)-encapsulated ATM permanent virtual circuits (PVCs).
Do not use this feature on a router that initiates PPPoA sessions.
PPPoA does not support static IP assignments within virtual templates.
The PPPoE autosense is supported only for SNAP-encapsulated sessions.
This feature supports ATM PVCs. Switched virtual circuits (SVCs) are not supported.
PPPoA/PPPoE autosense enables a router to distinguish between incoming PPPoA and PPPoE over ATM sessions and to create virtual access based on demand for both PPP types.
The Autosense of MUX/SNAP Encapsulation on ATM PVCs feature enables the PVC encapsulation type to be autosensed by the router. The router determines the encapsulation type of a PVC by looking at the encapsulation type of the first incoming packet. If the PVC encapsulation type is changed while the PPPoA or PPPoE session on the network access server (NAS) is still up, the incoming packet is dropped, the encapsulation type is reset to autosense, and all sessions are removed from the PVC. The next incoming packet will then determine the new encapsulation type of the PVC.
The Autosense of PPPoA/PPPoE for MUX or SNAP Encapsulation feature provides resource allocation on demand. For each PVC configured for both PPPoA and PPPoE, certain resources (including one virtual-access interface) are allocated upon configuration, regardless of the existence of a PPPoA or PPPoE session on that PVC. With the Autosense of MUX/SNAP Encapsulation and PPPoA/PPPoE on ATM PVCs feature, resources are allocated for PPPoA and PPPoE sessions only when a client initiates a session, thus reducing overhead on the network access server (NAS).
This feature also saves configuration time by eliminating the need to specify the encapsulation type when ATM PVCs are being provisioned and by eliminating the need to manually provision ATM PVCs each time the encapsulation type changes.
Perform this task to configure PPPoA/PPPoE Autosense on a PVC.
| Command or Action | Purpose | |
|---|---|---|
|
Step 1 |
enable Example: |
Enables privileged EXEC mode.
|
|
Step 2 |
configure terminal Example: |
Enters global configuration mode. |
|
Step 3 |
interface atm number [. subinterface-number {multipoint | point-to-point }] Example: |
Specifies the ATM interface and optional subinterface and enters subinterface configuration mode. |
|
Step 4 |
pvc [name ] vpi / vci Example: |
Configures a PVC on the ATM interface or subinterface and enters ATM VC configuration mode. |
|
Step 5 |
encapsulation aal5autoppp virtual-template number Example: |
Configures PPPoA/PPPoE autosense on the PVC.
|
|
Step 6 |
end Example: |
Ends the session and enters privileged EXEC mode. |
 Note |
Virtual-access interfaces for PPPoE sessions are cloned from the virtual template interface specified in the virtual private dialup network (VPDN) group. |
| Command or Action | Purpose | |
|---|---|---|
|
Step 1 |
enable Example: |
Enables privileged EXEC mode.
|
|
Step 2 |
configure terminal Example: |
Enters global configuration mode. |
|
Step 3 |
vc-class atm vc-class-name Example: |
Creates and names a map class and enters VC class configuration mode. |
|
Step 4 |
encapsulation aal5autoppp virtual-template number Example: |
Configures PPPoA/PPPoE autosense.
|
|
Step 5 |
exit Example: |
Returns to global configuration mode. |
|
Step 6 |
interface atm number [. subinterface-number {multipoint | point-to-point }] Example: |
Specifies the ATM interface and enters subinterface configuration mode. |
|
Step 7 |
class-int vc-class-name Example: |
Applies the VC class to all VCs on the ATM interface or subinterface. |
|
Step 8 |
end Example: |
Ends the session and enters privileged EXEC mode. |
|
Step 9 |
show running-config Example: |
Verifies whether the PPPoA/PPPoE autosense configuration is successful. |
To troubleshoot PPP sessions establishment, use the following commands:
debug ppp authentication
debug ppp negotiation
To troubleshoot the establishment of PPP sessions that are authenticated by a RADIUS or TACACS server, use the following commands:
debug aaa authentication
debug aaa authorization
 Caution |
Use debug commands with extreme caution because they are CPU-intensive and can seriously impact your network. |
Perform this task to monitor and maintain PPPoA/PPPoE autosense for ATM PVCs. The show commands can be used in any order.
| Command or Action | Purpose | |
|---|---|---|
|
Step 1 |
enable Example: |
Enables privileged EXEC mode.
|
|
Step 2 |
show atm pvc [ppp ] Example: |
Checks that the PVC contains the PPPoA session after the client at the other end of the PVC has initiated a PPPoA session. |
|
Step 3 |
show caller Example: |
Displays caller information.
|
|
Step 4 |
show interface virtual-access interface-number Example: |
Displays information about the virtual-access interface, link control protocol, protocol states, and interface statistics.
|
|
Step 5 |
show user Example: |
Displays information about the active lines on the router. |
|
Step 6 |
show vpdn Example: |
Displays basic information about all active VPDN tunnels. |
The following example shows how to configure the NAS with PPPoA/PPPoE autosense on PVC 30/33:
! Configure PPP Autosense
!
interface atm 0/0/0.33 multipoint
pvc 30/33
encapsulation aal5autoppp virtual-template 1
protocol pppoe
!
interface virtual-template 1
ip unnumbered fastethernet 0/0/0
ip route-cache cef
!
interface fastethernet 0/0/0
ip address 10.1.1.1 255.255.255.0
!The following example shows how to configure the NAS with PPPoA/PPPoE autosense on the VC class called MyClass. The MyClass VC class applies PPPoA/PPPoE autosense to all PVCs on the ATM 0/0/0.99 interface.
! Configure PPP Autosense
!
vc-class atm MyClass
encapsulation aal5autoppp virtual-template 1
!
interface atm 0/0/0.99 multipoint
class-int MyClass
no ip directed-broadcast
pvc 20/40
pvc 30/33
protocol pppoe
!
interface virtual-template 1
ip unnumbered fastethernet 0/0/0
ip route-cache cef
!
interface fastethernet 0/0/0
ip address 10.1.1.1 255.255.255.0
!The following example shows how to handle PPPoA and PPPoE sessions separately using two virtual templates:
interface atm 0/0/0.3 multipoint
no ip directed-broadcast
class-int pppauto
!
interface atm 0/0/0.9 multipoint
ip address 10.16.40.1 255.255.0.0
no ip directed-broadcast
!
interface virtual-template 1
ip unnumbered atm 0/0/0.9
ip route-cache cef
no ip directed-broadcast
peer default ip address pool pool-1
ppp authentication pap
!
interface virtual-template 2
ip unnumbered atm 0/0/0.9
ip route-cache cef
no ip directed-broadcast
peer default ip address pool pool-2
ppp authentication chap
!
interface fastethernet 0/0/0
ip address 10.1.1.1 255.255.255.0
!
vc-class atm pppauto
encapsulation aal5autoppp virtual-template 2
!Note |
Whenever possible, configure PPPoA and PPPoE to use the same virtual template. Using separate virtual templates leads to the inefficient use of virtual access because the maximum number of virtual-access interfaces will have to be precloned twice: once for PPPoE and once for PPPoA. If PPPoA and PPPoE use the same virtual template, the maximum number of virtual-access interfaces can be precloned once and used for PPPoA and PPPoE as needed. |
The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.|
Feature Name |
Releases |
Feature Information |
|---|---|---|
|
PPPoA/PPPoE Autosense for ATM PVCs |
Cisco IOS XE Release 3.3S |
The PPPoA/PPPoE Autosense for ATM PVCs feature enables a router to distinguish between incoming PPP over ATM (PPPoA) and PPP over Ethernet (PPPoE) over ATM sessions and to create virtual access based on demand for both PPP types. |
|
Autosense of MUX/SNAP Encapsulation and PPPoA/PPPoE on ATM PVCs |
Cisco IOS XE Release 3.3S |
The Autosense of MUX/SNAP Encapsulation and PPPoA/PPPoE on ATM PVCs feature enhances PPP over ATM (PPPoA)/PPP over Ethernet (PPPoE) autosense functionality by providing autosense support on MUX- and SNAP-encapsulated ATM permanent virtual circuits (PVCs). The following command was introduced or modified: encapsulation aal5autoppp virtual-template . |
cloning --Creating and configuring a virtual-access interface by applying a specific virtual template interface. The template is the source of the generic user information and router-dependent information. The result of cloning is a virtual-access interface configured with all the commands in the template.
LCP --Link Control Protocol. Protocol that establishes, configures, and tests data-link connections for use by PPP.
NAS --network access server. A device providing local network access to users across a remote access network such as the public switched telephone network (PSTN).
PPP --Point-to-Point Protocol. A protocol that encapsulates network layer protocol information over point-to-point links. PPP is defined in RFC 1661.
PPPoA --PPP over ATM.
PPPoE --PPP over Ethernet.
precloning --Cloning a specified number of virtual-access interfaces from a virtual template at system startup or when the command is configured.
PVC --permanent virtual circuit (or connection). Virtual circuit that is permanently established. PVCs save bandwidth associated with circuit establishment and teardown in situations where certain virtual circuits must exist all the time. In ATM terminology, called a permanent virtual connection.
VC --virtual channel. Logical circuit created to ensure reliable communication between two network devices. A VC is defined by a VPI/VCI pair and can be either permanent (PVC) or switched (SVC).
virtual-access interface --Instance of a unique virtual interface that is created dynamically and exists temporarily. Virtual-access interfaces can be created and configured differently by different applications, such as virtual profiles and virtual private dialup networks. Virtual-access interfaces are cloned from virtual template interfaces.
virtual template interface --A logical interface configured with generic configuration information for a specific purpose or configuration common to specific users, plus router-dependent information. The template takes the form of a list of Cisco IOS interface commands that are applied to virtual-access interfaces, as needed.
VPDN --virtual private dialup network. A system that permits dial-in networks to exist remotely from home networks, while giving the appearance of being directly connected.
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