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This chapter describes how to configure an Asynchronous Transfer Mode (ATM) interface in the Cisco 7000 series routers and Cisco 4500 routers, and how to configure a serial interface for ATM access in other routers.
For routers that will use a serial interface for ATM access through an ATM data service unit (ADSU), the chapter explains the steps necessary to enable Asynchronous Transfer Mode-Data Exchange Interface (ATM-DXI) encapsulation, select a multiprotocol encapsulation method using ATM-DXI, and set up a permanent virtual circuit (PVC) for the selected encapsulation.
For Cisco 7000 routers that have an ATM Interface Processor (AIP), the chapter explains the steps necessary to configure the AIP, PVCs, and switched virtual circuits (SVCs).
For Cisco 4500 routers that have an ATM network processor module (NPM), this chapter explains the steps necessary to configure the ATM, PVCs, and SVCs.
For a complete description of the commands in this chapter, refer to the "ATM Commands" chapter of the Router Products Command Reference publication. For background information about ATM, see the Internetworking Technology Overview publication.
ATM is a cell-switching and multiplexing technology designed to combine the benefits of circuit switching (constant transmission delay and guaranteed capacity) with those of packet switching (flexibility and efficiency for intermittent traffic).
Cisco provides ATM access in two ways, depending on the hardware available in the router:
In routers outside the Cisco 4500 and the Cisco 7000 series, a serial interface can be configured for multiprotocol encapsulation over ATM-DXI, as specified by RFC 1483. This standard describes two methods of transporting multiprotocol connectionless network interconnect traffic over an ATM network. One method allows multiplexing of multiple protocols over a single PVC. The other method uses different virtual circuits to carry different protocols. Our implementation supports transport of AppleTalk, Banyan VINES, IP, and Novell IPX traffic.
In routers outside the Cisco 4500 and the Cisco 7000 series, an ATM data service unit (ADSU) is required to provide the ATM interface to the network, to compute the DXI Frame Address (DFA) from the virtual path identifier (VPI) and virtual channel identifier (VCI) values defined for the protocol or protocols carried on the PVC, to convert outgoing packets into ATM cells, and to reassemble incoming ATM cells into packets.
Cisco's AIP provides a single ATM network interface for the Cisco 7000 series router. Network interfaces for the Cisco 7000 reside on modular interface processors, which provide a direct connection between the high-speed Cisco Extended Bus (CxBus) and the external networks. The maximum number of AIPs that the Cisco 7000 supports depends on the bandwidth configured. The total bandwidth through all the AIPs in the system should be limited to 200 Mbps full duplex (two TAXI interfaces, or one SONET and one E3, or one SONET and one lightly used SONET, five E3s, or four T3s).
Cisco's network processor module (NPM) provides a single ATM interface for the Cisco 4500 routers. PLIMs that support SONET/SDH 155 mbps are available for both single-mode and multimode fiber. A single NPM can be installed in the Cisco 4500 router.
For a complete description of the Cisco 7000 and AIP, refer to the Cisco 7000 Hardware Installation and Maintenance publication. The AIP is compatible with any Cisco 7000 that is running Cisco Internetwork Operating System (Cisco IOS) Release 10 or later. For a complete description of the Cisco 4500 and the NPM, refer to the Cisco 4000 Series Hardware Installation and Maintenance manual and the Installing NPMs in the Cisco 4000 Series manual.
ATM is a connection-oriented environment. All traffic to or from an ATM network is prefaced with a virtual path identifier (VPI) and virtual channel identifier (VCI). A VPI/VCI pair is considered a single virtual circuit. Each virtual circuit is a private connection to another node on the ATM network. Each virtual circuit is treated as a point-to-point mechanism to another router or host and is capable of supporting bidirectional traffic.
Each ATM node is required to establish a separate connection to every other node in the ATM network that it wishes to communicate with. All such connections are established using a PVC or an SVC with an ATM signaling mechanism. This signaling is based on the ATM Forum UNI Specification V3.0.
Each virtual circuit is considered a complete and separate link to a destination node. Users can encapsulate data as they see fit across the connection. The ATM network disregards the contents of the data. The only requirement is that data be sent to the AIP card in a manner that follows the specific ATM adaptation layer (AAL) format.
An AAL defines the conversion of user information into cells. That is, an AAL segments upper-layer information into cells at the transmitter and reassembles the cells at the receiver. AAL1 and AAL2 handle isochronous traffic, such as voice and video, and are not relevant to the router. AAL3/4 and AAL5 support data communications; that is, they segment and reassemble packets. Starting with Release 10.2, Cisco supports both AAL3/4 and AAL5 on the Cisco 7000 series. Starting with Release 10.3(4), Cisco supports AAL5 on the Cisco 4500.
An ATM connection is simply used to transfer raw bits of information to a destination router/host. The ATM router takes the common part convergence sublayer (CPCS) frame, carves it up into 53-byte cells and sends these cells to the destination router or host for reassembly. Forty-eight bytes of each cell are used for the CPCS data; the remaining 5 bytes are used for cell routing. The 5-byte cell header contains the destination VPI/VCI, payload type, cell loss priority (CLP), and header error control.
The ATM network is actually considered a local-area network (LAN) with high bandwidth availability. Each end node in the ATM network is a host on a specific subnet. All end nodes wishing to communicate with each other must be within the same subnet in the network.
Unlike a LAN, which is connectionless, ATM requires certain features to provide a LAN environment to the users. One such feature is broadcast capability. Protocols wishing to broadcast packets to all stations in a subnet must be allowed to do so with a single call to Layer 2. In order to support broadcasting, the router allows the user to specify a particular virtual circuit as a broadcast virtual circuit. When the protocol passes a packet with a broadcast address to the drivers, the packet is duplicated and sent to each virtual circuit marked as a broadcast virtual circuit. This method is known as pseudobroadcasting.
This section provides an overview of the ATM features, interfaces, microcode, and virtual circuits available on the Cisco 7000.
The AIP supports the following features:
Process-switched bridging over ATM supports AAL3/4-SMDS encapsulated packets only. All frames that originate at or are forwarded by the router are sent as 802.3 bridge frames without Frame Check Sequence (FCS) (RFC 1483 bridge frame formats with 0x0007 in the PID field of the SNAP header). You can enable process-switched bridging for Switched Multimegabit Data Service (SMDS) as described later in this chapter.
Fast-switched transparent bridging over ATM supports AAL5-SNAP encapsulated packets only. All bridged AAL5-SNAP encapsulated packets are fast switched. Fast-switched transparent bridging supports Ethernet, FDDI, and Token Ring packets sent in AAL5-SNAP encapsulation over ATM. You can enable fast-switched bridging for AAL5-SNAP as described later in this chapter.
All ATM interfaces are full duplex. You must use the appropriate ATM interface cable to connect the AIP with an external ATM network. Refer to the Asynchronous Transfer Mode Interface Processor (AIP) Installation and Configuration publication for descriptions of ATM connectors.
The AIP provides an interface to ATM switching fabrics for transmitting and receiving data at rates of up to 155 Mbps bidirectionally; the actual rate is determined by the physical layer interface module (PLIM). The PLIM contains the interface to the ATM cable. The AIP can support PLIMs that connect to the following physical layers:
For wide-area networking, ATM is currently being standardized for use in Broadband Integrated Services Digital Networks (BISDNs) by the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) and the American National Standards Institute (ANSI). BISDN supports rates from E3 (34 Mbps) to multiple gigabits per second (gbps).
The AIP microcode is a software image that provides card-specific software instructions. An onboard ROM component contains the default AIP microcode. The Cisco 7000 supports downloadable microcode, which enables you to upgrade microcode versions by loading new microcode images onto the Route Processor (RP), storing them in Flash memory, and instructing the AIP to load an image from Flash memory instead of the default ROM image. You can store multiple images for an interface type and instruct the system to load any one of them or the default ROM image with a configuration command. All processor modules of the same type will load the same microcode image from either the default ROM image or from a single image stored in Flash memory.
Although multiple microcode versions for a specific interface type can be stored concurrently in Flash memory, only one image can load at startup. The show controller cxbus command displays the currently loaded and running microcode version for the switch processor (SP) and for each IP. The show running-config command shows the current system instructions for loading microcode at startup.
For a complete description of microcode and downloading procedures, refer to the Asynchronous Transfer Mode Interface Processor (AIP) Installation and Configuration publication.
A virtual circuit is a connection between remote hosts and routers. A virtual circuit is established for each ATM end node with which the router communicates. The characteristics of the virtual circuit are established when the virtual circuit is created and include the following:
Each virtual circuit supports the following router functions:
By default, fast switching is enabled on all AIP interfaces. These switching features can be turned off with interface configuration commands. Autonomous switching must be explicitly enabled per interface.
This section provides an overview of the ATM features, interfaces, and virtual circuits available on the Cisco 4500.
The NPM supports the following features:
An ATM adaptation layer (AAL) defines the conversion of user information into cells. That is, it segments upper-layer information into cells at the transmitter and reassembles them at the receiver. AAL1 and AAL2 handle isochronous traffic, such as voice and video, and are not relevant to the router. AAL3/4 and AAL5 support data communications; that is, they segment and reassemble packets. Release 11.0 supports AAL5 on the Cisco 4500.
All ATM interfaces are full duplex. You must use the appropriate ATM interface cable to connect the NPM with an external ATM network. Refer to the Cisco 4000 Series Hardware Installation and Maintenance manual and the Installing NPMs in the Cisco 4000 Series manual for descriptions of ATM connectors.
The NPM provides an interface to ATM switching fabrics for transmitting and receiving data at rates of up to 155 Mbps bidirectionally; the actual rate is determined by the physical layer interface module (PLIM). The PLIM contains the interface to the ATM cable. The NPM can support PLIMs that connect to the following physical layers:
For wide-area networking, ATM is currently being standardized for use in Broadband Integrated Services Digital Networks (BISDNs) by the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) and the American National Standards Institute (ANSI). BISDN supports rates from E3 (34 Mbps) to multiple gigabits per second (gbps).
A virtual circuit is a point-to-point connection between remote hosts and routers. A virtual circuit is established for each ATM end node with which the router communicates. The characteristics of the virtual circuit are established when the virtual circuit is created and include the following:
Each virtual circuit supports the following router functions:
Our routers provide ATM access in two ways, depending on the hardware available in the router:
In routers other than the Cisco 7000 series, a serial interface can be configured for multiprotocol encapsulation over ATM-DXI, as specified by RFC 1483. ATM-DXI encapsulation allows a DCE and a DTE to cooperate to provide a User-Network Interface for ATM networks. At the ADSU, the DXI header is stripped off, and the protocol data is segmented into cells for transport over the ATM network.
RFC 1483 describes two methods of transporting multiprotocol connectionless network interconnect traffic over an ATM network. One method allows multiplexing of multiple protocols over a single PVC. The other method uses different virtual circuits to carry different protocols. Our implementation of RFC 1483 supports both methods and supports transport of Apollo Domain, AppleTalk, Banyan VINES, DECnet, IP, Novell IPX, ISO CLNS, and XNS traffic.
In routers other than the Cisco 7000 series, an ADSU is required to provide the ATM interface to the network, convert outgoing packets into ATM cells, and reassemble incoming ATM cells into packets.
To configure ATM access over a serial interface on routers outside the Cisco 7000 series, complete the tasks in the following sections. The first four tasks are required.
Step 2 Enable ATM-DXI Encapsulation
Step 3 Set Up the ATM-DXI PVC
Step 4 Map Protocol Addresses to the ATM-DXI PVC
Step 5 Monitor and Maintain the ATM-DXI Serial Interface
To begin configuring the serial interface for ATM access, enable the serial interface by performing the following steps beginning in global configuration mode:
| 1This command is documented in the "AppleTalk Commands" chapter of the Router Products Command Reference publication.
2This command is documented in the "IP Commands" chapter of the Router Products Command Reference publication. 3This command is documented in the "Novell IPX Commands" chapter of the Router Products Command Reference publication. |
The supported protocols are Apollo Domain, AppleTalk, Banyan VINES, DECnet, IP, Novell IPX, ISO CLNS, and XNS.
For information about the addressing requirements of a protocol, see the relevant protocol chapter of this publication.
To enable ATM-DXI encapsulation on a serial or HSSI interface, perform the following task in interface configuration mode:
An ATM-DXI PVC can be defined to carry one protocol, multiple protocols as described by RFC 1490, or multiple protocols as described by RFC 1483.
To set up the ATM-DXI PVC, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
The MUX option defines the PVC to carry one protocol only; each protocol must be carried over a different PVC. The NLPID option is multiprotocol encapsulation, compatible with RFC 1490; this option is provided for backward compatibility with default setting in earlier versions of the Cisco IOS. The SNAP option is LLC/SNAP multiprotocol encapsulation, compatible with RFC 1483; SNAP is the current default option.
Note The default encapsulation was NLPID in software earlier than Release 10.3. In this release, the default encapsulation is SNAP. Select the nlpid option now if you had previously selected the default.
This section describes how to map protocol addresses to the VCI and the VPI of a PVC that can carry multiprotocol traffic. The protocol addresses belong to the host at the other end of the link. To map a protocol address to an ATM-DXI PVC, complete the following task in interface configuration mode:
| Task | Command |
|---|---|
Repeat this task for each protocol to be carried on the PVC.
The supported protocols are Apollo Domain, AppleTalk, Banyan VINES, DECnet, IP, Novell IPX, ISO CLNS, and XNS.
For an example of configuring a serial interface for ATM, see the "ATM Access over a Serial Interface Example" section later in this chapter.
After configuring the serial interface for ATM, you can display the status of the interface, the ATM-DXI PVC, or the ATM-DXI map. To display interface, PVC, or map information, complete the following tasks in EXEC mode:
| Task | Command |
|---|---|
To configure ATM on the AIP in Cisco 7000 series routers, complete the tasks in the following sections. The first task is required, and then you must configure at least one PVC or SVC. The virtual circuit options you configure must match in three places: on the router, on the ATM switch, and at the remote end of the PVC or SVC connection.
See the "Cisco 7000 ATM Configuration Examples" section for configuration examples.
This section describes how to begin configuring the AIP. The Cisco 7000 identifies an interface address by its slot number (slots 0 to 4) and port number in the format slot/port. Because each AIP contains a single ATM interface, the port number is always 0. For example, the slot/port address of an ATM interface on an AIP installed in slot 1 is 1/0.
To begin to configure the AIP, start the following task in privileged EXEC mode:
| 1This command is documented in the "System Image, Microcode Image, and Configuration File Load Commands" chapter of the Router Products Command Reference publication.
2This command is documented in the "Interface Commands" chapter of the Router Products Command Reference publication. 3This command is documented in the "IP Commands" chapter of the Router Products Command Reference publication. |
To enable the AIP, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Change the shutdown state to up and enable the ATM interface, thereby starting the SAR operation on the interface. |
| 1This command is documented in the "Interface Commands" chapter of the Router Products Command Reference publication. |
The no shutdown command passes an enable command to the AIP, which then begins segmentation and reassembly (SAR) operations. It also causes the AIP to configure itself based on the previous configuration commands sent.
You can customize the AIP. The features you can customize have default values that will most likely suit your environment and probably need not be changed. However, you might need to enter configuration commands, depending upon the requirements for your system configuration and the protocols you plan to route on the interface. Perform the task in the following sections if you need to customize the AIP:
A rate queue defines the speed at which individual virtual circuits will transmit data to the remote end. You can configure permanent rate queues, allow the software to set up dynamic rate queues, or some combination of the two. The software dynamically creates rate queues when an atm pvc command specifies a peak/average rate that does not match any user-configured rate queue. The software will dynamically create all rate queues if you have not configured any.
The Cisco IOS software automatically creates rate queues as necessary to satisfy the requests of atm pvc commands. The peak rate for a VCD is set to the maximum that the PLIM will allow, and the average rate is set equal to the peak rate; then a rate queue is dynamically created for the peak rate of the VCD.
If dynamic rate queues do not satisfy your traffic shaping needs, you can configure permanent rate queues.
See the "Dynamic Rate Queue Examples (Cisco 7000)" section for examples of different rate queues created in response to atm pvc commands.
The AIP supports up to eight different peak rates. The peak rate is the maximum rate, in kilobits per second, at which a virtual circuit can transmit. Once attached to this rate queue, the virtual circuit is assumed to have its peak rate set to that of the rate queue. The rate queues are broken into a high priority (0 through 3) and low priority (4 through 7) bank.
You can configure each permanent rate queue independently to a portion of the overall bandwidth available on the ATM link. The combined bandwidths of all rate queues should not exceed the total bandwidth available. A warning message is displayed if you attempt to configure the combined rate queues beyond what is available to the AIP. The total bandwidth depends on the PLIM (see the "AIP Interface Types" section).
To set a permanent rate queue, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Configure a permanent rate queue, which defines the maximum speed at which an individual virtual circuit transmits data to a remote ATM host. |
Each interface has a default maximum packet size or maximum transmission unit (MTU) size. On the AIP, this number defaults to 4470 bytes; the maximum is 9188 bytes. To set the maximum MTU size, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
| 1This command is documented in the "Interface Commands" chapter of the Router Products Command Reference publication. |
The default SONET PLIM is STS-3C.To set the SONET PLIM to STM-1, perform the following task in interface configuration mode:
To loop all packets back to the AIP instead of the network, perform the following task in interface configuration mode:
The exception queue is used for reporting ATM events, such as CRC errors. By default, it holds 32 entries; the range is 8 to 256. It is unlikely you will need to configure the exception-queue length; if you do, perform the following task in interface configuration mode:
By default, the ATM interface allows the maximum of 4096 virtual circuits. However, you can configure a lower number, thereby limiting the number of virtual circuits on which the AIP allows segmentation and reassembly to occur. Limiting the number of virtual circuits does not affect the VPI/VCI of each virtual circuit.
To set the maximum number of virtual circuits supported (including PVCs and SVCs), perform the following task in interface configuration mode:
Message identifier (MID) numbers are used by receiving devices to reassemble cells from multiple sources into packets.
To ensure that the message identifiers will be unique at the receiving end and, therefore, that messages can be reassembled correctly, you can limit the number of message identifiers allowed on a virtual circuit and assign different ranges of message identifiers to different PVCs.
To limit the number of message identifier numbers allowed on each virtual circuit and to assign different ranges of message identifiers to different PVCs, complete the following tasks in interface configuration mode:
The maximum number of message identifiers per virtual circuit is set at 16 by default, and may take only the values 16, 32, 64, 128, 256, 512, or 1024.
The default value for both midlow and midhigh is zero.
The raw queue is used for raw ATM cells, which include operation and maintenance (OAM) and Interim Local Management Interface (ILMI) cells. ILMI is a means of passing information to the router including information about virtual connections and addresses.
The raw-queue size is in the range of 8 to 256 cells; the default is 32 cells. To set the raw-queue size, perform the following task in interface configuration mode:
The number of receive buffers determines the maximum number of reassemblies that the AIP can perform simultaneously. The number of buffers defaults to 256, although it can be in the range from 0 to 512. To set the number of receive buffers, perform the following task in interface configuration mode:
The number of transmit buffers determines the maximum number of fragmentations that the AIP can perform simultaneously. The number of buffers defaults to 256, although it can be in the range from 0 to 512. To set the number of transmit buffers, perform the following task in interface configuration mode:
By default, the AIP supports 1024 VCIs per VPI. This value can be in the range of 1 to 4096.This value controls the memory allocation in the AIP to deal with the VCI table. It defines only the maximum number of VCIs to support per VPI; it does not bound the VCI numbers.
To set the maximum number of VCIs to support per VPI, perform the following task in interface configuration mode:
The VP filter allows you to specify which VPI or range of VPIs will be used for AAL3/4 processing. The default value of the AIP's VP filter register is 0x7B. To set the AIP VP filter register, perform the following task in interface configuration mode:
By default, the AIP expects the ATM switch to provide transmit clocking. To specify that the AIP generate the transmit clock internally for SONET and E3 PLIM operation, perform the following task in interface configuration mode:
If you are going to use a permanent virtual circuit (PVC), the PVC must be configured into both the router and the ATM switch. PVCs remain active until the circuit is removed from either configuration.
All virtual circuit characteristics listed in the section "Virtual Circuits" earlier in this chapter apply to these PVCs. When a PVC is configured, all the configuration options are passed on to the AIP. These PVCs are writable into the nonvolatile RAM (NVRAM) as part of the RP configuration and are used when the RP image is reloaded.
Some ATM switches might have point-to-multipoint PVCs that do the equivalent of broadcasting. If a point-to-multipoint PVC exists, then that PVC can be used as the sole broadcast PVC for all multicast requests.
To configure a PVC, you must perform the tasks in the following sections:
To create a PVC on the AIP interface, perform the following task in interface configuration mode:
When you create a PVC, you create a virtual circuit descriptor (VCD) and attach it to the VPI and VCI. A VCD is an AIP-specific mechanism that identifies to the AIP which VPI/VCI to use for a particular packet. The AIP requires this feature to manage the packets, for transmission. The number chosen for the VCD is independent of the VPI/VCI used.
When you create a PVC, you also specify the AAL and encapsulation. A rate queue is used that matches the peak and average rate selections, which are specified in kilobits per second. Omitting a peak and average value causes the PVC to be connected to the highest bandwidth rate queue available. In this case, the peak and average values are equal.
See examples of PVC configurations in the section "Cisco 7000 ATM Configuration Examples" at the end of this chapter.
The ATM interface supports a static mapping scheme that identifies the ATM address of remote hosts or routers. This address is specified as a virtual circuit descriptor (VCD) for a PVC (or an NSAP address for SVC operation). This section describes how to map a PVC to an address, which is a required task if you are configuring a PVC.
You enter mapping commands as groups. You first create a map list and then associate it with an interface. Begin the following tasks in global configuration mode:
| 1This command is documented in the "Interface Commands" chapter of the Router Products Command Reference publication. |
A map list can contain multiple map entries, as steps 2 and 3 in the preceding task table illustrate. The broadcast keyword specifies that this map entry is to be used when the corresponding protocol wants to send broadcast packets to the interface (for example, any network routing protocol updates). If you do not specify broadcast, the ATM software is prevented from sending routing protocol updates to the remote hosts.
Step 5 illustrates that when the map list is complete, the list is then associated with an ATM interface by using the same name argument.
You can create multiple map lists, but only one map list can be associated with an interface. Different map lists can be associated with different interfaces. See the examples at the end of this chapter.
ATM switched virtual circuit (SVC) service operates much like X.25 SVC service, although ATM allows much higher throughput. Virtual circuits are created and released dynamically, providing user bandwidth on demand. This service requires a signaling protocol between the router and the switch.
The ATM signaling software provides a method of dynamically establishing, maintaining, and clearing ATM connections at the User-Network Interface (UNI). The ATM signaling software conforms to ATM Forum UNI 3.0.
In UNI mode, the user is the router and the network is an ATM switch. This is an important distinction. The Cisco router does not perform ATM-level routing; the ATM switch does the ATM routing. The router is used primarily as a LAN interconnection device. The router is viewed as the user at the end of the circuit, and the ATM switch is viewed as the network.
Figure 7-1 illustrates the router position in a basic ATM environment. The router is used primarily to interconnect LANs via an ATM network. The workstation connected directly to the destination ATM switch illustrates that you can connect not only routers to ATM switches, but also any computer with an ATM interface that conforms to ATM Forum UNI specification.
You must complete the tasks in the following sections if you are going to use SVCs:
The tasks in the following sections are optional SVC tasks for customizing your network. These tasks are considered advanced; the default values are almost always adequate. You should not have to perform these tasks unless you really need to customize your particular SVC connection.
Unlike X.25 service, which uses in-band signaling (connection establishment done on the same circuit as data transfer), ATM uses out-of-band signaling. This means that one dedicated PVC exists between the router and the ATM switch, over which all SVC call establishment and call termination requests flow. After the call is established, data transfer occurs over the SVC, from router to router. The signaling that accomplishes the call setup and tear down is called Layer 3 signaling or Q.2931 protocol.
The out-of-band signaling method means that an SVC requires that a PVC be configured. Figure 7-2 illustrates a signaling PVC from the source router to the ATM switch used to set up two SVCs. This is a fully meshed network; workstations A, B, and C all can communicate with each other.
To configure the signaling PVC for all SVC connections, perform the following task in interface configuration mode:
See the section "SVCs in a Fully Meshed Network Example (Cisco 7000)" at the end of this chapter for a sample ATM signaling configuration.
Every ATM interface involved with signaling must be configured with an NSAP address. The NSAP address is the ATM address of the interface and must be unique across the network.
ATM NSAP addresses have a fixed length of 40 hexadecimal digits. You must configure the complete address in hexadecimal format; that is, each digit entered represents a hexadecimal digit. To represent the complete NSAP address, you must enter 40 hexadecimal digits in the following format:
Note All ATM NSAP addresses must be entered in the dotted hexadecimal format shown, which conforms to the UNI specification.
There is no default NSAP address for the interface, which is why you must configure the NSAP address for SVCs. To set the ATM interface's source NSAP address, perform the following task in interface configuration mode:
The following example assigns NSAP address AB.CDEF.01.234567.890A.BCDE.F012.3456.7890.1234.12 to ATM interface 4/0:
You can display the ATM address for the interface by executing the show interface atm slot /0 command.
The tasks in this section are optional and advanced. The ATM signaling software can specify to the AIP card and the ATM switch a limit on how much traffic the source router will be sending. It provides this information in the form of traffic parameters. (These parameters have default values.) The ATM switch in turn sends these parameters as requested by the source to the ATM destination node. If the destination cannot provide such capacity levels, the call may fail (for Cisco 7000 series behavior, see the per-interface atm sig-traffic-shaping strict command in the Router Products Command Reference). There is a single attempt to match traffic parameters.
This section describes how to change traffic values to customize your SVC connection. The individual tasks that separately specify peak, sustainable, or burst values for an SVC are analogous to the peak, average, and burst values defined when you create a PVC. Valid values for the peak rate on the AIP are between 130 kbps and the PLIM rate. The valid values for the average rate are fractions of the peak rate—the peak rate divided by a number between 1 and 64. When the average rate is below one-half the peak rate, the average rate defaults to the next available fraction. The valid range for the maximum burst size is between 32 cells and 2016 cells. Values between 32 and 2016 will round up to the next multiple of 32 cells.
Forward commands apply to the flow of cells from the source router to the destination router. Backward commands apply to the flow of cells from the destination router to the source router.
Most of the SVC traffic parameters include the concept of cell loss priority (CLP). CLP defines two levels of cell importance:
Figure 7-3 illustrates a source and a destination router implementing traffic settings that correspond end-to-end. The value for the forward command at the source router corresponds to the value for the backward command at the destination router.
To change the traffic parameters, perform one or more of the following tasks in map-class configuration mode:
The Service Specific Connection Oriented Protocol (SSCOP) resides in the service specific convergence sublayer (SSCS) of the ATM adaptation layer (AAL). SSCOP is used to transfer variable-length service data units (SDUs) between users of SSCOP. SSCOP provides for the recovery of lost or corrupted SDUs.
Note The tasks in this section customize the SSCOP feature to a particular network or environment and are optional. The features have default values and will be valid in most installations. Before customizing these features, you should have a good understanding of SSCOP and the network involved.
The poll timer controls the maximum time between transmission of a POLL PDU when SD or SDP PDUs are queued for transmission or are outstanding pending acknowledgments. To change the poll timer from the default value of 10 seconds, perform the following task in interface configuration mode:
The keepalive timer controls the maximum time between transmission of a POLL PDU when no SD or SDP PDUs are queued for transmission or are outstanding pending acknowledgments. To change the keepalive timer from the default value of 30 seconds, perform the following task in interface configuration mode:
The connection control timer determines the time between transmission of BGN, END, or RS PDUs as long as an acknowledgment has not been received. Connection control performs the establishment, release, and resynchronization of an SSCOP connection.
To change the connection control timer from the default value of 10 seconds, perform the following task in interface configuration mode:
To change the retry count of the connection control timer from the default value of 10, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Set the number of times that SSCOP will retry to transmit BGN, END, or RS PDUs when they have not been acknowledged. |
A transmit window controls how many packets can be transmitted before an acknowledgment is required. To change the transmitter's window from the default value of 7, perform the following task in interface configuration mode:
A receive window controls how many packets can be received before an acknowledgment is required. To change the receiver's window from the default value of 7, perform the following task in interface configuration mode:
Since the AIP does not perform packet-level accounting on a per-VC basis, the interface does not close an idle SVC automatically. You must perform this task in EXEC mode if you want to close a particular SVC:
You can specify that an SVC be established on an ATM interface using only signaled traffic parameters. When you configure strict traffic-shaping on the router ATM interface, an SVC is established only if traffic shaping can be provided for the transmit cell flow per the signaled traffic parameters. If such shaping cannot be provided, the SVC is released.
If you do not configure strict traffic-shaping on the router ATM interface, an attempt is made to establish an SVC with traffic shaping for the transmit cell flow per the signaled traffic parameters. If such shaping cannot be provided, the SVC is installed with default shaping parameters; that is, it behaves as though a PVC were created without specifying traffic parameters.
To specify that an SVC be established on an ATM interface using only signaled traffic parameters, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Specify that an SVC be established on an ATM interface using only signaled traffic parameters. |
An AAL defines the conversion of user information into cells. That is, it segments upper-layer information into cells at the transmitter and reassembles them at the receiver. AAL1 and AAL2 handle isochronous traffic, such as voice and video, and are not relevant to the router. AAL3/4 and AAL5 support data communications; that is, they segment and reassemble packets. Release 10.2 supports both AAL3/4 and AAL5.
Our implementation of the AAL3/4 encapsulates each AAL3/4 packet in an SMDS header and trailer. This feature supports both unicast and multicast addressing, and provides subinterfaces for multiple AAL3/4 connections over the same physical interface.
Note Each subinterface configured to support AAL3/4 is allowed only one SMDS E.164 unicast address and one E.164 multicast address. The multicast address is used for all broadcast operations. In addition, only one virtual circuit is allowed on each subinterface that is being used for AAL3/4 processing, and it must be an AAL3/4 virtual circuit.
Support for AAL3/4 on an ATM interface requires static mapping of all protocols except IP. However, dynamic routing of IP can coexist with static mapping of other protocols on the same ATM interface.
To configure an ATM interface for SMDS networks, perform the following tasks in interface configuration mode:
The VP filter provides a mechanism for specifying which VPIs (or a range of VPIs) will be used for AAL3/4 processing during datagram reassembly. All other VPIs are mapped to AAL5 processing. For more information about the way the command works and the effect of selecting specific values, refer to the Router Products Command Reference publication.
After configuring the ATM interface for SMDS networks, configure the interface for standard protocol configurations, as needed. For more information about protocol configuration, refer to the relevant chapters of this manual.
For examples of configuring an ATM interface for AAL3/4 support, see the "PVC Examples with AAL3/4 and SMDS Encapsulation" section later in this chapter.
Our implementation of bridging over ATM allows the spanning tree for an interface to support both of two different types of MAC addresses: E.164 addresses for AAL 3/4-SMDS, and virtual circuit descriptors (VCDs) for AAL5 LLC-SNAP.
Our bridging implementation supports only IEEE 802.3 frame formats. The router can accept IEEE 802.3 frames with Frame Check Sequence (FCS) or without FCS. When the router receives frames with FCS (RFC 1483 bridge frame formats with 0x0001 in the PID field of the SNAP header), it strips off the FCS and forwards the frame as necessary. All frames that originate or are forwarded by the router are sent as 802.3 bridge frames without FCS (RFC bridge frame formats with 0x0007 in the PID field of the SNAP header).
This implementation performs process-level switching; it does not support fast bridging.
Note This feature works only on AAL3/4-SMDS encapsulations and AAL5-LLC/SNAP PVCs. AAL5-MUX and AAL5-NLPID bridging is not yet supported. It also does not operate in a switched virtual circuit environment.
To configure transparent bridging for AAL3/4 SMDS subinterfaces, complete the following steps beginning in interface configuration mode.
| Task | Command |
|---|---|
| Step 1. Specify an AIP interface. | |
| Step 2. Assign a source IP address and subnet mask to the interface. | |
| Step 3. Enable an AAL3/4 (SMDS) subinterface. | |
| Step 4. Configure a VP filter for the affected ATM subinterface. | |
| Step 5. Provide an SMDS E.164 unicast address for the subinterface. | |
| Step 6. Provide an SMDS E.164 multicast address. | |
| Step 7. Create an AAL3/4 PVC. | |
| Step 8. Assign the interface to a bridge group. | |
| Step 9. Return to global configuration mode. | |
| Step 10. Define the type of spanning tree protocol as DEC. | bridge group protocol dec2 |
| 1This command is documented in the "IP Commands" chapter of the Router Products Command Reference publication.
2This command is documented in the "Transparent Bridging Commands" chapter of the Router Products Command Reference publication. |
No other configuration steps are required. All spanning tree updates will be sent to the multicast E.164 address specified in Step 6. Routers on the remote end will learn the unicast address of this router from the packets this router sends to them.
For an example of transparent bridging for an SMDS interface, see the "PVC with AAL3/4 and SMDS Encapsulation Examples (Cisco 7000)" section.
To configure transparent bridging for LLC/SNAP PVCs, compete the following steps beginning in interface configuration mode:
| Task | Command |
|---|---|
| Step 1. Specify an AIP interface. | |
| Step 2. Assign a source IP address and subnet mask to the interface. | |
| Step 3. Create one or more PVCs using AAL5-SNAP encapsulation. | |
| Step 4. Assign the interface to a bridge group. | |
| Step 5. Return to global configuration mode. | |
| Step 6. Define the type of spanning tree protocol as DEC. | bridge group protocol dec2 |
| 1This command is documented in the "IP Commands" chapter of the Router Products Command Reference publication.
2This command is documented in the "Transparent Bridging Commands" chapter of the Router Products Command Reference publication. |
No other configuration is required. Spanning tree updates will be broadcast to all AAL5-SNAP virtual circuits that exist on the ATM interface. Only the AAL5-SNAP virtual circuits on the specific subinterface will receive the updates. The router will not send spanning tree updates to AAL5-MUX and AAL5-NLPID virtual circuits.
For an example of transparent bridging for an AAL5-SNAP PVC, see the "Transparent Bridging on an AAL5-SNAP PVC Example (Cisco 7000)" section.
To configure ATM in Cisco 4500 routers, complete the tasks in the following sections. The first task is required, and then you must configure at least one PVC or SVC. The virtual circuit options you configure must match in three places: on the router, on the ATM switch, and at the remote end of the PVC or SVC connection. The remaining tasks are optional.
See the "Cisco 4500 ATM Configuration Examples" section for configuration examples.
This section describes how to begin configuring the NPM. The Cisco 4500 identifies an interface address by its unit number.
To begin to configure the NPM, start the following task in privileged EXEC mode:
| 1This command is documented in the "System Image, Microcode Image, and Configuration File Load Commands" chapter of the Router Products Command Reference publication.
2This command is documented in the "Interface Commands" chapter of the Router Products Command Reference publication. 3This command is documented in the "IP Commands" chapter of the Router Products Command Reference publication. |
To enable the ATM interface, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Change the shutdown state to up and enable the ATM interface, thereby starting the SAR operation on the interface. |
| 1This command is documented in the "Interface Commands" chapter of the Router Products Command Reference publication. |
The no shutdown command passes an enable command to the NPM, which then begins segmentation and reassembly (SAR) operations. It also causes the NPM to configure itself based on the previous configuration commands sent.
If you are going to use a permanent virtual circuit (PVC), the PVC must be configured into both the router and the ATM switch. PVCs remain active until the circuit is removed from either configuration.
All virtual circuit characteristics listed in the section "Virtual Circuits" earlier in this chapter apply to these PVCs. When a PVC is configured, all the configuration options are passed on to the NPM. These PVCs are writable into the nonvolatile RAM (NVRAM) as part of the Route Processor (RP) configuration and are used when the RP image is reloaded.
Some ATM switches might have point-to-multipoint PVCs that do the equivalent of broadcasting. If a point-to-multipoint PVC exists, then that PVC can be used as the sole broadcast PVC for all multicast requests.
To configure a PVC, perform the tasks in the following sections. The first two tasks are required; the third task is optional:
To create a PVC on the AIP interface, perform the following task in interface configuration mode:
When you create a PVC, you create a virtual circuit descriptor (VCD) and attach it to the VPI and VCI. A VCD is an NPM-specific mechanism that identifies to the NPM which VPI/VCI to use for a particular packet. The NPM requires this feature to manage the packets, for transmission. The number chosen for the VCD is independent of the VPI/VCI used.
When you create a PVC, you also specify the AAL and encapsulation. A rate queue is used that matches the peak and average rate selections, which are specified in kilobits per second. Omitting a peak and average value causes the PVC to be connected to the highest bandwidth rate queue available. In this case, the peak and average values are equal.
See examples of PVC configurations on the Cisco 4500 in the section "Cisco 4500 ATM Configuration Examples" at the end of this chapter.
The ATM interface supports a static mapping scheme that identifies the ATM address of remote hosts or routers. This address is specified as a virtual circuit descriptor (VCD) for a PVC (or an NSAP address for SVC operation). This section describes how to map a PVC to an address, which is a required task if you are configuring a PVC.
You enter mapping commands as groups. You first create a map list and then associate it with an interface. Begin the following tasks in global configuration mode
| 1This command is documented in the "Interface Commands" chapter of the Router Products Command Reference publication. |
A map list can contain multiple map entries, as Steps 2 and 3 in the preceding task table illustrate. The broadcast keyword specifies that this map entry is to be used when the corresponding protocol must send broadcast packets to the interface (for example, any network routing protocol updates). If you do not specify broadcast, the ATM software is prevented from sending routing protocol updates to the remote host.
Step 5 illustrates that when the map list is complete, the list is then associated with an ATM interface by using the same name argument.
You can create multiple map lists, but you can associate only one map list with an interface. Different map lists can be associated with different interfaces. See the examples at the end of this chapter.
You can optionally configure the PVC to send OAM F5 loopback cells to verify connectivity on the virtual circuit. The remote end must respond by echoing back such cells.
To configure the transmission of OAM F5 loopback cells, add the oam keyword to the atm pvc command, as shown in the following task:
| Task | Command |
|---|---|
Configure transmission of OAM F5 cells on the PVC, specifying how often OAM F5 cells should be sent. |
atm pvc vcd vpi vci aal-encap [[midlow midhigh] |
ATM switched virtual circuit (SVC) service operates much like X.25 SVC service, although ATM allows much higher throughput. Virtual circuits are created and released dynamically, providing user bandwidth on demand. This service requires a signaling protocol between the router and the switch.
The ATM signaling software provides a method of dynamically establishing, maintaining, and clearing ATM connections at the User-Network Interface (UNI). The ATM signaling software conforms to ATM Forum UNI 3.0.
In UNI mode, the user is the router and the network is an ATM switch. This is an important distinction. The Cisco router does not perform ATM-level call routing; the ATM switch does the ATM call routing. The router routes packets through the resulting circuit. The router is viewed as the user and the LAN interconnection device at the end of the circuit, and the ATM switch is viewed as the network.
Figure 7-4 illustrates the router position in a basic ATM environment. The router is used primarily to interconnect LANs via an ATM network. The workstation connected directly to the destination ATM switch illustrates that you can connect not only routers to ATM switches, but also any computer with an ATM interface that conforms to ATM Forum UNI specification.
You must complete the tasks in the following sections if you are going to use SVCs:
The tasks in the following sections are optional SVC tasks for customizing your network. These tasks are considered advanced; the default values are almost always adequate. You should not have to perform these tasks unless you need to customize your particular SVC connection.
Unlike X.25 service, which uses in-band signaling (connection establishment done on the same circuit as data transfer), ATM uses out-of-band signaling. This means that one dedicated PVC exists between the router and the ATM switch, over which all SVC call establishment and call termination requests flow. After the call is established, data transfer occurs over the SVC, from router to router. The signaling that accomplishes the call setup and teardown is called Layer 3 signaling or Q.2931 protocol.
For out-of-band signaling, a signaling PVC must be configured before any SVCs can be set up. Figure 7-5 illustrates a signaling PVC from the source router to the ATM switch used to set up two SVCs. This is a fully meshed network; workstations A, B, and C all can communicate with each other.
To configure the signaling PVC for all SVC connections, perform the following task in interface configuration mode:
The VPI and VCI values must be configured consistently with the local switch. The standard value of VPI is 0; the standard value of VCI is 5.
See the section "SVCs in a Fully Meshed Network Example (Cisco 4500)" at the end of this chapter for a sample ATM signaling configuration.
Every ATM interface involved with signaling must be configured with an NSAP address. The NSAP address is the ATM address of the interface and must be unique across the network.
ATM NSAP addresses have a fixed length of 40 hexadecimal digits. You must configure the complete address in hexadecimal format; that is, each digit entered represents a hexadecimal digit. To represent the complete NSAP address, you must enter 40 hexadecimal digits in the following format:
Note All ATM NSAP addresses must be entered in the dotted hexadecimal format shown, which conforms to the UNI specification.
Because the interface has no default NSAP address, you must configure the NSAP address for SVCs. To set the ATM interface's source NSAP address, perform the following task in interface configuration mode:
The following example assigns NSAP address AB.CDEF.01.234567.890A.BCDE.F012.3456.7890.1234.12 to ATM interface 4/0:
You can display the ATM address for the interface by executing the show interface atm number command.
The tasks in this section are optional and advanced. The ATM signaling software can specify to the AIP card and the ATM switch a limit on how much traffic the source router will be sending. It provides this information in the form of traffic parameters. (These parameters have default values.) The ATM switch in turn sends these parameters as requested by the source to the ATM destination node. If the destination cannot provide such capacity levels, the call may fail (for Cisco 4500 series behavior, see the per-interface atm sig-traffic-shaping strict command in the Router Products Command Reference). There is a single attempt to match traffic parameters.
This section describes how to change traffic values to customize your SVC connection. The individual tasks that separately specify peak, sustainable, or burst values for an SVC are analogous to the peak, average, and burst values defined when you create a PVC. The valid values for the average rate are fractions of the peak rate—the peak rate divided by a number between 1 and 64. When the average rate is below one-half the peak rate, the average rate defaults to the next available fraction. The valid range for the maximum burst size is between 32 cells and 2016 cells. Values between 32 and 2016 will round up to the next multiple of 32 cells.
Forward commands apply to the flow of cells from the source router to the destination router. Backward commands apply to the flow of cells from the destination router to the source router.
Most of the SVC traffic parameters include the concept of cell loss priority (CLP). CLP defines two levels of cell importance:
Figure 7-6 illustrates a source and a destination router implementing traffic settings that correspond end-to-end. The value for the forward command at the source router corresponds to the value for the backward command at the destination router.
To change the traffic values from their default values, perform one or more of the following tasks in map-class configuration mode:
The Service Specific Connection Oriented Protocol (SSCOP) resides in the service specific convergence sublayer (SSCS) of the ATM adaptation layer (AAL). SSCOP is used to transfer variable-length service data units (SDUs) between users of SSCOP. SSCOP provides for the recovery of lost or corrupted SDUs.
Note The tasks in this section customize the SSCOP feature to a particular network or environment and are optional. The features have default values andare valid in most installations. Before customizing these features, you should have a good understanding of SSCOP and the network involved.
The poll timer controls the maximum time between transmission of a POLL PDU when SD or SDP PDUs are queued for transmission or are outstanding pending acknowledgments. To change the poll timer from the default value of 10 seconds, perform the following task in interface configuration mode:
The keepalive timer controls the maximum time between transmission of a POLL PDU when no SD or SDP PDUs are queued for transmission or are outstanding pending acknowledgments. To change the keepalive timer from the default value of 30 seconds, perform the following task in interface configuration mode:
The connection control timer determines the time between transmission of BGN, END, or RS PDUs as long as an acknowledgment has not been received. Connection control performs the establishment, release, and resynchronization of an SSCOP connection.
To change the connection control timer from the default value of 10 seconds, perform the following task in interface configuration mode:
To change the retry count of the connection control timer from the default value of 10, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Set the number of times that SSCOP will retry to transmit BGN, END, or RS PDUs when they have not been acknowledged. |
A transmit window controls how many packets can be transmitted before an acknowledgment is required. To change the transmitter's window from the default value of 7, perform the following task in interface configuration mode:
A receive window controls how many packets can be received before an acknowledgment is required. To change the receiver's window from the default value of 7, perform the following task in interface configuration mode:
You can disconnect an idle SVC by completing the following task in EXEC mode:
You can specify that an SVC be established on an ATM interface using only signaled traffic parameters. When you configure strict traffic-shaping on the router ATM interface, an SVC is established only if traffic shaping can be provided for the transmit cell flow per the signaled traffic parameters. If such shaping cannot be provided, the SVC is released.
If you do not configure strict traffic-shaping on the router ATM interface, an attempt is made to establish an SVC with traffic shaping for the transmit cell flow per the signaled traffic parameters. If such shaping cannot be provided, the SVC is installed with default shaping parameters; that is, it behaves as though a PVC were created without specifying traffic parameters.
To specify that an SVC be established on an ATM interface using only signaled traffic parameters, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Specify that an SVC be established on an ATM interface using only signaled traffic parameters. |
You can customize the ATM interface on the Cisco 4500. The features you can customize have default values that will most likely suit your environment and probably need not be changed. However, you might need to enter configuration commands, depending upon the requirements for your system configuration and the protocols you plan to route on the interface. Perform the task in the following sections if you need to customize the NPM:
A rate queue defines the speed at which individual virtual circuits will transmit data to the remote end. You can configure permanent rate queues, allow the software to set up dynamic rate queues, or some combination of the two. The software dynamically creates rate queues when an atm pvc command specifies a peak/average rate that does not match any user-configured rate queue. The software dynamically creates all rate queues if you have not configured any.
The Cisco IOS software automatically creates rate queues as necessary to satisfy the requests of atm pvc commands. The peak rate for a VCD is set to the maximum that the PLIM will allow, and the average rate is set equal to the peak rate; then a rate queue is dynamically created for the peak rate of the VCD.
If dynamic rate queues do not satisfy your traffic shaping needs, you can configure permanent rate queues.
See the "Dynamic Rate Queue Examples (Cisco 4500)" section for examples of different rate queues created in response to atm pvc commands.
The NPM supports up to four different peak rates. The peak rate is the maximum rate, in kilobits per second, at which a virtual circuit can transmit. Once attached to this rate queue, the virtual circuit is assumed to have its peak rate set to that of the rate queue.
You can configure each permanent rate queue independently to a portion of the overall bandwidth available on the ATM link. The combined bandwidths of all rate queues should not exceed the total bandwidth available. A warning message is displayed if you attempt to configure the combined rate queues beyond what is available to the NPM. The total bandwidth depends on the PLIM (see the "NPM ATM Interface Types" section).
To set a permanent rate queue, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Configure a permanent rate queue, which defines the maximum speed at which an individual virtual circuit transmits data to a remote ATM host. |
Each interface has a default maximum packet size or maximum transmission unit (MTU) size. On the NPM, this number defaults to 4470 bytes; the maximum is 9188 bytes. To set the maximum MTU size, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
| 1This command is documented in the "Interface Commands" chapter of the Router Products Command Reference publication. |
The default SONET PLIM is STS-3C.To set the SONET PLIM to STM-1, perform the following task in interface configuration mode:
To loop all packets back to the NPM instead of the network, perform the following task in interface configuration mode:
To loop the incoming network packets back to the network, perform the following task in interface configuration mode:
By default, the NPM supports 1024 VCIs per VPI. This value can be any power of 2 in the range from 32 to 8192.This value controls the memory allocation in the NPM to deal with the VCI table.
To set the maximum number of VCIs to support per VPI, perform the following task in interface configuration mode:
The product of VC* VP is fixed at 8192; the number of virtual circuits supported per virtual path will decrease in proportion to an increase in the number of virtual paths.
By default, the NPM expects the ATM switch to provide transmit clocking. To specify that the AIP generate the transmit clock internally for SONET and E3 PLIM operation, perform the following task in interface configuration mode:
Our implementation of transparent bridging over ATM on hte Cisco 4500 allows the spanning tree for an interface to support virtual circuit descriptors (VCDs) for AAL5 LLC-SNAP as MAC addresses.
If the relevant interface or subinterface is explicitly put into a bridge group, as described in this section, AAL5-SNAP encapsulated bridge packets on a PVC are fast-switched.
Our bridging implementation supports IEEE 802.3 frame formats and IEEE 802.10 frame formats. The router can accept IEEE 802.3 frames with Frame Check Sequence (FCS) or without FCS. When the router receives frames with FCS (RFC 1483 bridge frame formats with 0x0001 in the PID field of the SNAP header), it strips off the FCS and forwards the frame as necessary. All IEEE 802.3 frames that originate or are forwarded by the router are sent as 802.3 bridge frames without FCS (bridge frame formats with 0x0007 in the PID field of the SNAP header).
Note Transparent bridging for ATM on the Cisco 4500 works only on AAL5-LLC/SNAP PVCs (fast-switched). AAL3/4-SMDS, AAL5-MUX, and AAL5-NLPID bridging is not yet supported on the Cisco 4500.Transparent bridging for ATM also does not operate in a switched virtual circuit environment.
To configure transparent bridging for LLC/SNAP PVCs, compete the following steps beginning in interface configuration mode:
| Task | Command |
|---|---|
| Step 1. Specify an AIP interface and, optionally, a subinterface. | |
| Step 2. Assign a source IP address and subnet mask to the interface, if needed. | |
| Step 3. Create one or more PVCs using AAL5-SNAP encapsulation. | |
| Step 4. Assign the interface to a bridge group. | |
| Step 5. Return to global configuration mode. | |
| Step 6. Define the type of spanning tree protocol as DEC. | bridge group protocol dec3 |
| 1This command is documented in the "Interface Commands" chapter of the Router Products Command Reference publication.
2This command is documented in the "IP Commands" chapter of the Router Products Command Reference publication. 3This command is documented in the "Transparent Bridging Commands" chapter of the Router Products Command Reference publication. |
No other configuration is required. Spanning tree updates are broadcast to all AAL5-SNAP virtual circuits that exist on the ATM interface. Only the AAL5-SNAP virtual circuits on the specific subinterface receive the updates. The router does not send spanning tree updates to AAL5-MUX and AAL5-NLPID virtual circuits.
For an example of transparent bridging for an AAL5-SNAP PVC, see the "Transparent Bridging on an AAL5-SNAP PVC Example (Cisco 4500)" section.
After configuring the new interface, you can display its status. You can also display the current state of the ATM network and connected virtual circuits. To show current virtual circuits and traffic information, perform the following tasks in EXEC mode:
| 1This command is documented in the "Interface Commands" chapter of the Router Products Command Reference publication. |
The example in this section illustrates how to configure a serial interface for ATM access.
In the following example, serial interface 0 is configured for ATM-DXI with MUX encapsulation. Because MUX encapsulation is used, only one protocol is carried on the PVC. This protocol is explicitly identified by a dxi map command, which also identifies the protocol address of the remote node. This PVC can carry IP broadcast traffic.
The examples in the following sections illustrate how to configure an ATM interface on the Cisco 7000:
The following example creates PVC 5 on ATM interface 3/0. It uses LLC/SNAP encapsulation over AAL5. The interface is at IP address 1.1.1.1 with 1.1.1.5 at the other end of the connection. The static map list named atm declares that the next node is a broadcast point for multicast packets from IP.
The following example is of a typical ATM configuration for a PVC:
Figure 7-7 illustrates a fully meshed network. The configurations for Routers A, B, and C follow the figure. In this example, the routers are configured to use PVCs. Fully meshed indicates that any workstation can communicate with any other workstation. Note that the two map-list statements configured in Router A identify the ATM addresses of Routers B and C. The two map-list statements in Router B identify the ATM addresses of Routers A and C. The two map list statements in Router C identify the ATM addresses of Routers A and B.
The following example is also a configuration for the fully meshed network shown in Figure 7-7, but this example uses SVCs. PVC 1 is the signaling PVC.
The following example provides a minimal configuration of an ATM interface to support AAL3/4 and SMDS encapsulation; no protocol configuration is shown:
The following example shows how IP dynamic routing might coexist with static routing of another protocol.
This example shows that IP configured is dynamically routed, but that AppleTalk is statically routed. An AppleTalk remote host is configured at address 10.2 and is associated with SMDS address c140.8111.1111.
AAL3/4 associates a protocol address with an SMDS address, as shown in the last line of this example. In contrast, AAL5 static maps associate a protocol address with a PVC number.
Both of the following examples assume that no permanent rate queues have been configured. The software dynamically creates rate queues when an atm pvc command specifies a peak/average rate that does not match any user-configured rate queue.
In the following example, the software sets the peak rate for VCD 1 to the maximum that the PLIM will allow and sets the average rate to the peak rate. Then it creates a rate queue for the peak rate of this VCD.
In the following example, the software creates a 100-Mbps rate queue and assigns VCD 2 to that rate queue with an average rate of 50 Mbps and a burst size of 64 cells.
In the following example, three AAL5-SNAP PVCs are created on the same ATM interface. The router will broadcast all spanning tree updates to these AAL5-SNAP PVCs. No other virtual circuits will receive spanning tree updates.
In the following example, the router will send all spanning tree updates to the multicast address e111.1111.1111.1111. Routers receiving packets from this router will learn its unicast SMDS address, c111.1111.1111.1111, by examining the packets.
The examples in the following sections illustrate how to configure an ATM interface on the Cisco 4500:
The following example creates PVC 5 on ATM interface 0. It uses LLC/SNAP encapsulation over AAL5. The interface is at IP address 1.1.1.1 with 1.1.1.5 at the other end of the connection. The static map list named atm declares that the next node is a broadcast point for multicast packets from IP.
The following example is of a typical ATM configuration for a PVC:
Figure 7-7 illustrates a fully meshed network. The configurations for Routers A, B, and C follow the figure. In this example, the routers are configured to use PVCs. Fully meshed indicates that any workstation can communicate with any other workstation. Note that the two map-list statements configured in Router A identify the ATM addresses of Routers B and C. The two map-list statements in Router B identify the ATM addresses of Routers A and C. The two map list statements in Router C identify the ATM addresses of Routers A and B.
The following example is also a configuration for the fully meshed network shown in Figure 7-7, but this example uses SVCs. PVC 1 is the signaling PVC.
Both of the following examples assume that no permanent rate queues have been configured. The software dynamically creates rate queues when an atm pvc command specifies a peak/average rate that does not match any user-configured rate queue.
In the following example, the software sets the peak rate for VCD 1 to the maximum that the PLIM will allow and sets the average rate to the peak rate. Then it creates a rate queue for the peak rate of this VCD.
In the following example, the software creates a 100-Mbps rate queue and assigns VCD 2 to that rate queue with an average rate of 50 Mbps and a burst size of 64 cells.
In the following example, three AAL5-SNAP PVCs are created on the same ATM interface. The router will broadcast all spanning tree updates to these AAL5-SNAP PVCs. No other virtual circuits will receive spanning tree updates.
Posted: Wed Jul 2 23:44:22 PDT 2003
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