Table Of Contents

ATM Network Interfaces

Configuration of Interface Types

ATM Network Interfaces Example

UNI Interfaces

NNI Interfaces

IISP Interfaces

ATM Network Interfaces

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This chapter provides descriptions of the various ATM network interface types you can configure on the ATM switch router, along with their applications. An overview of the configuration for each type is also included.

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Note The information in this chapter is applicable to the Catalyst 8540 MSR, Catalyst 8510 MSR, and LightStream 1010 ATM switch routers. For detailed configuration information, refer to the ATM Switch Router Software Configuration Guide and the ATM Switch Router Command Reference publication.

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This chapter includes the following sections:

• Configuration of Interface Types

• ATM Network Interfaces Example

• UNI Interfaces

• NNI Interfaces

• IISP Interfaces

Configuration of Interface Types

When your ATM switch router is initially powered on, without any previous configuration, Integrated Local Management Interface (ILMI) autoconfiguration senses the peer interface type and appropriately configures the interface on the ATM switch router. The following ATM interface parameters are automatically configured on the physical ports:

•ATM network interface (UNI, NNI)

•Interface type (private, public)

•UNI version (3.0, 3.1, 4.0)

•UNI side (network, user)

Explicitly configuring interfaces is the alternative to ILMI autoconfiguration. You can accept the default ATM interface configuration or override it.

ATM Network Interfaces Example

The example network shown in Figure 3-1 illustrates some standard ATM interface configurations. The subsequent sections of this chapter explain the various interface types shown here.

Figure 3-1 Example Network Configuration

The network configuration in Figure 3-1 shows three campus buildings (finance, engineering, and headquarters) connected by an ATM backbone of private NNI links. A public UNI link using a VP tunnel connects through the WAN to a remote sales office.

UNI Interfaces

The UNI specification defines communications between ATM end systems (such as workstations and routers) and ATM switches in private ATM networks. Figure 3-2 shows a private UNI interface between the ATM switch router (HB-1) in the headquarters building and a router with an ATM interface (HB-1) in the same building.

Figure 3-2 Private UNI Example

The UNI interface in Figure 3-2 has the following attributes:

•Type—The interface is a private one, as it is between two devices in the same private network.

•Side—The ATM switch router end of the interface is the network side; the router end is the user side.

•Version—The UNI version could be 3.0, 3.1, or 4.0.

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Tips When connecting with non-Cisco equipment, you should verify that the UNI version is the same on both ends of a connection. Version negotiation can occasionally fail with nonstandard switches.

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Configuration Overview

Configuring an interface as UNI allows the interface to do UNI signaling, used in setting up switched connections. You only need to manually configure a UNI interface when you need to change the autoconfigured values. Configuring the UNI interface requires the following steps:

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Step 1 Disable autoconfiguration on the interface.

Because autoconfiguration negotiates the UNI parameters for the interface, this feature must be disabled before performing manual configuration.

Step 2 Configure the UNI side, type, and version on the interface.

The user side is the device with the ATM network interface, such as a router or workstation; the network side is the ATM switch. The type and version must be the same on both ends. For a description of the features supported in each of the UNI versions, see the "ATM Signaling Protocols—UNI and NNI" section.

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NNI Interfaces

The Network-Network Interface (NNI) specification defines communications between two ATM switches in a private ATM network. Figure 3-3 shows a private NNI interface from the ATM switch router (HB-1) in the headquarters building to the ATM switch router (EB-1) in the engineering building.

Figure 3-3 Private NNI Example

The NNI interface in Figure 3-3 is a private one, because it connects devices within a private network. The concept of public and private NNIs is, however, useful only for description purposes. It is not a part of the actual configuration. Also, because NNI interfaces connect two ATM switches, both sides are network.

Configuration Overview

Configuring an interface as NNI allows the interface to do NNI signaling for route discovery and topology analysis. You only need to configure an NNI interface when you must change it from its autoconfigured default. Configuring an NNI interface requires the following steps:

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Step 1 Disable autoconfiguration on the interface.

Step 2 Specify the interface as NNI.

Step 3 Modify the maximum VPI bits configuration (optional).

The default VPI bit space for NNI interfaces is 8, which allows a maximum of 255 VPIs. On some platforms you can increase the VPI bit space to 12, for a total of 4095 VPIs. See the "VPI/VCI Ranges for SVCs" section.

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IISP Interfaces

The Interim Interswitch Signaling Protocol (IISP) defines a static routing protocol for use between ATM switches. IISP was designed as an interim routing protocol prior to PNNI and now provides support for switched virtual connections (SVCs) on switches that do not support PNNI.

Figure 3-4 shows an IISP between the ATM switch router (SB-1) in the remote sales office and the ATM switch router (SB-1) in the same office.

Figure 3-4 IISP Network Segment Example

The IISP interface in Figure 3-4 has the following attributes:

•Side—Because both ATM switches are within a private network, one arbitrarily takes the role of the user side, while the other takes the network side.

•Version—The UNI version could be 3.0, 3.1, or 4.0.

Configuration Overview

You only need to configure an IISP interface when you want to do static routing rather than the autoconfigured PNNI protocol that runs by default over NNI interfaces. Configuring an IISP interface requires the following steps:

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Step 1 Disable autoconfiguration on the interface.

Step 2 Configure the interface as IISP and specify the UNI side and version.

Because there is no ILMI on IISP interfaces, these parameters must be manually configured. One interface is the user side, while the other is the network side. The versions should match on both devices.

Step 3 Configure the ATM route address prefix.

Specify the 13-byte address prefix of the destination interface for the static route.

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For further information on IISP configuration, see Chapter 7, "ATM Routing with IISP and PNNI."