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In Cisco IOS Release 12.0(1)T, you configured the IETF-compliant PPP over ATM feature to enable IETF-compliant PPP over ATM with VC multiplexed encapsulation. Now, with the IETF PPP over ATM LLC Encapsulation feature in Cisco IOS Release 12.0(2)T, you can configure IETF-compliant PPP over ATM with LLC encapsulation. Both of these features comply with the IETF document titled PPP over AAL5 (RFC 2364).
IETF PPP over ATM LLC Encapsulation 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 interworking.
By configuring IETF PPP over ATM LLC Encapsulation, you also enable a VC to carry multiprotocol traffic. For example, a VC will carry both PPP and IPX traffic simultaneously, and an LLC or LLC/SNAP header will differentiate between the PPP and IPX traffic.
Figure 1 shows Frame Relay to ATM interworking.
The IETF PPP over ATM LLC Encapsulation feature allows you to configure ATM to Frame Relay service interworking and enable a VC to carry multiprotocol traffic.
Asynchronous Transfer Mode (ATM)---International standard for cell relay in which multiple service types (such as voice, video, or data) are conveyed in fixed-length (53-byte) cells. Fixed-length cells allow cell processing to occur in hardware, thereby reducing transit delays. ATM is designed to take advantage of high-speed transmission media such as E3, SONET, and T3.
command line interface (CLI)---Interface that allows the user to interact with the operating system by entering commands and optional arguments. The UNIX operating system and DOS provide CLIs.
Internet Engineering Task Force (IETF)---Task force consisting of over 80 working groups responsible for developing Internet standards. The IETF operates under the auspices of the Internet Society (ISOC).
Internetwork Packet Exchange (IPX)---NetWare network layer (Layer 3) protocol used for transferring data from servers to workstations. IPX is similar to IP and XNS.
Logical Link Control (LLC)---Higher of the two data link layer sublayers defined by the IEEE. The LLC sublayer handles error control, flow control, framing, and MAC-sublayer addressing. The most prevalent LLC protocol is IEEE 802.2, which includes both connectionless and connection-oriented variants.
permanent virtual circuit (PVC)---Virtual circuit that is permanently established. PVCs save bandwidth associated with circuit establishment and tear down in situations where certain virtual circuits must exist all the time. In ATM terminology, it is also called a permanent virtual connection.
Point-to-Point Protocol (PPP)---Successor to SLIP that provides router-to-router and host-to-network connections over synchronous and asynchronous circuits. Whereas SLIP was designed to work with IP, PPP was designed to work with several network layer protocols, such as IP, IPX, and ARA. PPP also has built-in security mechanisms, such as CHAP and PAP. PPP relies on two protocols: LCP and NCP.
Subnetwork Access Protocol (SNAP)---Internet protocol that operates between a network entity in the subnetwork and a network entity in the end system. SNAP specifies a standard method of encapsulating IP datagrams and ARP messages on IEEE networks. The SNAP entity in the end system makes use of the services of the subnetwork and performs three key functions: data transfer, connection management, and QoS selection.
switched virtual circuit (SVC)---Virtual circuit that is dynamically established on demand and is torn down when transmission is complete. SVCs are used in situations where data transmission is sporadic. In ATM terminology, it is also called a switched virtual connection.
virtual circuit (VC)---Logical circuit created to ensure reliable communication between two network devices. A virtual circuit is defined by a VPI/VCI pair, and can be either permanent (PVC) or switched (SVC). Virtual circuits are used in Frame Relay and X.25. In ATM terminology, a virtual circuit is also called a virtual channel.
The following restrictions apply to this feature for Cisco IOS Release 12.0(2)T:
IETF PPP over ATM LLC Encapsulation is supported on these platforms:
None
To configure IETF PPP over ATM LLC Encapsulation, use the following commands starting in global configuration mode:
| Step | Command | Purpose | ||
|---|---|---|---|---|
| interface atm slot/0.subinterface-number multipoint or interface atm number.subinterface-number multipoint | Specify an ATM multipoint subinterface using the appropriate format of the interface atm command.1 | ||
| pvc [name] vpi/vci | Configure the PVC. | ||
| encapsulation aal5snap2 | Configure LLC SNAP encapsulation. | ||
| protocol ppp virtual-template number | Configure IETF PPP over ATM LLC Encapsulation. |
You can also configure IETF PPP over ATM LLC Encapsulation 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 "Configure VC Classes" in the chapter "Configuring ATM" of the Wide-Area Networking Configuration Guide for Cisco IOS Release 12.0.
You can only configure IETF PPP over ATM LLC Encapsulation using the new ATM CLI. For general information about configuring PVCs using the new ATM CLI, see the chapter "Configuring ATM" in the Wide-Area Networking Configuration Guide for Cisco IOS Release 12.0.
For information about IETF-compliant PPP over ATM with VC multiplexed encapsulation, refer to the document called IETF-Compliant PPP over ATM for Cisco IOS Release 12.0(1)T. For information about Cisco's proprietary PPP over ATM, refer to the same document as well as to the section "Configure PPP over ATM" in the chapter "Configuring ATM" of the Wide-Area Networking Configuration Guide for Cisco IOS Release 12.0.
This section provides the following examples for configuring IETF PPP over ATM LLC Encapsulation:
This example configures IETF PPP over ATM LLC Encapsulation in the VC class called ppp-default. The VC class specifies virtual template 1 from which to spawn PPP interfaces, aal5snap encapsulation (the default), and a UBR class traffic type at 256 kbps. When ppp-default is configured on interface 0.1, PVC 0/70 inherits these properties. PVC 0/80 overrides virtual template 1 in the VC class and uses virtual template 2 instead. PVC 0/90 also overrides virtual template 1 and uses virtual template 3 instead. In addition, PVC 0/90 uses a VC multiplexed encapsulation and a UBR class traffic type at 500 kbps.
Router(config)# interface atm 0.1 multipoint Router(config-if)# class ppp-default ! Router(config-if)# pvc 0/70 Router(config-if-atm-vc)# exit ! Router(config-if)# pvc 0/80 Router(config-if-atm-vc)# protocol ppp virtual-template 2 Router(config-if-atm-vc)# exit ! Router(config-if)# pvc 0/90 Router(config-if-atm-vc)# encapsulation aal5mux ppp virtual-template 3 Router(config-if-atm-vc)# ubr 500 Router(config-if-atm-vc)# exit Router(config-if)# exit ! Router(config)# vc-class atm ppp-default Router(config-vc-class)# protocol ppp virtual-template 1 Router(config-vc-class)# ubr 256 Router(config-vc-class)# exit Router(config)#
This example illustrates how you can use inheritance to override a virtual template configuration for aal5mux ppp or aal5ciscoppp encapsulations. For PVC 5/505, since the encapsulation at that level is aal5ciscoppp virtual template 1, as specified in the VC class called muxppp, the protocol ppp virtual-template 2 command overrides only the virtual-template configuration.
Router(config)# interface atm 2/0 Router(config-if)# class muxppp ! Router(config-if)# pvc 5/505 Router(config-if-atm-vc)# protocol ppp virtual-template 2 Router(config-if-atm-vc)# exit ! Router(config)# vc-class muxppp Router(config-vc-class)# encapsulation aal5ciscoppp virtual-template 1 Router(config-vc-class)# exit Router(config)#
This example shows you how to limit the configuration of a particular LLC encapsulated protocol to a particular VC. First, we see that the VC class called ppp is configured with IETF PPP over ATM with LLC encapsulation and virtual template 1. This VC class is then applied to ATM interface 1/0/0. By configuring aal5snap encapsulation by itself on PVC 0/32, you disable IETF PPP over ATM with LLC encapsulation on this particular PVC; PVC 0/32 will only carry IP.
Router(config)# interface atm 1/0/0 Router(config-if)# class ppp Router(config-if)# exit ! Router(config)# interface atm 1/0/0.100 point-to-point Router(config-if)# description IP only VC Router(config-if)# ip address 10.1.1.1 255.255.255.0 Router(config-if)# pvc 0/32 Router(config-if-atm-vc)# encapsulation aal5snap Router(config-if-atm-vc)# exit Router(config-if)# exit ! Router(config)# vc-class atm ppp Router(config-vc-class)# encapsulation aal5snap Router(config-vc-class)# protocol ppp virtual-template 1 Router(config-vc-class)# exit Router(config)#
This section describes the modified protocol command. In Cisco IOS Release 12.0(2)T, you can configure this command for IETF-compliant PPP over ATM LLC encapsulation.
Use the protocol command in the appropriate command mode to do one or more of the following:
Use the no form of this command to remove a static map, disable Inverse ARP, or remove PPP over ATM with LLC encapsulation.
protocol protocol {protocol-address | inarp} [[no] broadcast] [virtual-template number]
protocol | Choose one of the following keywords: aarp---AppleTalk ARP apollo---Apollo domain appletalk---AppleTalk arp---IP ARP bridge---bridging bstun---block serial tunnel cdp---Cisco Discovery Protocol clns---ISO CLNS clns_es---ISO CLNS end system clns_is---ISO CLNS intermediate system cmns---ISO CMNS compressedtcp---Compressed TCP decnet---DECnet decnet_node---DECnet node decnet_prime_router---DECnet prime router decnet_router-l1---DECnet router L1 |
| decnet_router-l2---DECnet router L2 dlsw---data link switching ip---IP ipx---Novell IPX llc2---llc2 pad---PAD links ppp---encapsulation keyword for IETF-compliant PPP over ATM with LLC encapsulation qllc---Qualified Logical Link Control protocol rsrb---remote source-route bridging snapshot---snapshot routing support stun---serial tunnel vines---Banyan VINES xns---Xerox Network Systems protocol |
protocol-address | Destination address that is being mapped to a PVC. |
inarp | (Only valid for IP and IPX protocols on PVCs) Use this keyword to enable Inverse ARP on an ATM PVC. If you specify a protocol-address instead of inarp, Inverse ARP is automatically disabled for that protocol. |
[no] broadcast | (Optional) broadcast indicates that this map entry is used when the corresponding protocol sends broadcast packets to the interface-. For example, IGRP updates. Pseudobroadcasting is supported. The broadcast keyword of the protocol command takes precedence if you previously configured the broadcast command on the ATM PVC or SVC. |
virtual-template number | (Optional. You will only use these keywords and argument when you specify ppp encapsulation for the protocol argument.) Specifies which virtual template number to use. |
Inverse ARP is enabled for IP and IPX if the protocol is running on the interface and no static map is configured.
Interface-ATM-VC configuration (for an ATM PVC or SVC)
VC-class configuration (for a VC class)
This command first appeared in Cisco IOS Release 11.3 T.
This command allows you to configure IETF-compliant PPP over ATM with LLC encapsulation starting with Cisco IOS Release 12.0(2)T.
If the protocol command is not explicitly configured on an ATM PVC or SVC, the VC inherits the following default configuration (listed in order of next highest precedence):
Although you may assign an explicit network layer address to a virtual-template interface, we recommend that you consider two other procedures. One procedure is to use AAA to assign an address to the virtual-access interface created from the virtual template, instead of configuring any network-layer address on the virtual template. The other procedure is to use an unnumbered IP address on the virtual template.
When you use virtual profiles in PPP over ATM, fast-switching is supported.
It is currently not possible to disable a virtual access on an individual basis. To achieve a similar effect, either delete the relevant RADIUS user entries or deconfigure the VC associated with the virtual access.
The following example creates a static map on a VC, indicates that 192.68.34.237 is connected to this VC, and sends ATM pseudobroadcasts:
protocol ip 192.68.34.237 broadcast
The following example enables Inverse ARP for IPX and does not send ATM pseudobroadcasts:
protocol ipx inarp no broadcast
The following example removes a static map from a VC and restores the default behavior for Inverse ARP (Refer to the "Default" section described above):
no protocol ip 192.68.34.237
The following example configure IETF PPP over ATM with LLC encapsulation on an ATM PVC.
interface atm 0.1 multipoint pvc 0/99 encapsulation aal5snap protocol ppp virtual-template 1
This example illustrates how you can use inheritance to override a virtual template configuration for aal5mux ppp or aal5ciscoppp encapsulations. For PVC 5/505, since the encapsulation at that level is aal5ciscoppp virtual template 1, as specified in the VC class called muxppp, the protocol ppp virtual-template 2 command overrides only the virtual-template configuration.
interface atm 2/0 class muxppp ! pvc 5/505 protocol ppp virtual-template 2 ! vc-class muxppp encapsulation aal5ciscoppp virtual-template 1
Posted: Thu Mar 4 16:18:22 PST 1999
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