Table of Contents

Configuring LAN Emulation

This chapter describes LAN emulation (LANE) and how to configure it on the ATM switch router.

Note   This chapter provides advanced configuration instructions for the Catalyst 8540 MSR, Catalyst 8510 MSR, and LightStream 1010 ATM switch routers. For an overview of LANE architecture and operation, refer to the Guide to ATM Technology. For complete descriptions of the commands mentioned in this chapter, refer to the ATM Switch Router Command Reference publication. For a detailed description of LANE and its components, refer to Cisco  IOS Switching Services Configuration Guide: Virtual LANs.

This chapter contains the following sections:

LANE Functionality and Requirements

LANE uses ATM as a backbone to interconnect existing legacy LANs. In doing so, LANE allows legacy LAN users to take advantage of ATM's benefits without requiring modifications to end station hardware or software.

Multiple emulated LANs (ELANs), which are logically separated, can share the same physical ATM network and the same physical ATM interface. LANE makes an ATM interface look like one or more separate Ethernet or Token Ring interfaces.

LANE services provide connectivity between ATM-attached devices and LAN-attached devices. Two primary applications for the LANE protocol are as follows:

Figure 13-1 illustrates the various connections LANE provides.

Refer to the Guide to ATM Technology for the following background topics on LANE:

LANE Router and Switch Router Requirements

You must manually configure Q.2931 over Signaling ATM Adaptation Layer (QSAAL) and ILMI signalling PVCs on routers and edge LAN switch routers to run LANE. However, these signalling permanent virtual channels (PVCs) are automatically configured on the ATM switch router.

Note   The Catalyst 8510 MSR and LightStream 1010 processor and port adapters can be installed in slots 9 through 13 of the Catalyst 5500 switch. In this case, no physical connection is required between the ATM port adapter and the LANE card if the ATM Fabric Integration Module is used.

At least one ATM switch router is required to run LANE. For example, you cannot run LANE on routers connected back-to-back.

LANE Configuration Tasks

Before you begin to configure LANE, you must decide whether you want to set up one or multiple emulated LANs. If you set up multiple emulated LANs, you must also decide where the servers and clients will be located, and whether to restrict the clients that can belong to each emulated LAN. The procedure for configuring bridged emulated LANs is the same as for any other LAN.

To configure LANE, complete the tasks in the following sections:

An ATM cloud can contain multiple configuration servers.

Every ELAN must have at least a LAN emulation server/broadcast-and unknown server (LES/BUS) pair, the maximum is 10. Every LANE cloud (one or multiple ELANs) must have at least one LAN emulation configuration server (LECS).

You can configure some emulated LANs with unrestricted membership and some emulated LANs with restricted membership. You can also configure a default emulated LAN, which must have unrestricted membership.

After LANE is configured, you can monitor and maintain the components, as described in the "Monitoring and Maintaining the LANE Components" section.

Creating a LANE Plan and Worksheet

Draw up a plan and a worksheet for your LANE scenario, containing the following information and leaving spaces for the ATM address of each LANE component on each subinterface of each participating router or switch router:

The last three items in this list are very important; they determine how you set up each emulated LAN in the configuration server database.

Automatic ATM Addressing and Address Templates for LANE Components

The ATM switch router automatically assigns ATM addresses to LANE components using the scheme described in the Guide to ATM Technology. You can also override the automatic address assignments using an ATM address template.

You can use ATM address templates in many LANE commands that assign ATM addresses to LANE components or that link client ATM addresses to emulated LANs. Using templates can greatly simplify the use of these commands.

Note   E.164-format ATM addresses do not support the use of LANE ATM address templates.

LANE ATM address templates can use two types of wildcards: an asterisk (*) to match any single character, and an ellipsis (...) to match any number of leading or trailing characters.

In LANE, a prefix template explicitly matches the prefix but uses wildcards for the end station interface (ESI) and selector fields. An ESI template explicitly matches the ESI field but uses wildcards for the prefix and selector fields. Table 13-1 shows how the values of unspecified digits are determined when an ATM address template is used.

Rules for Assigning Components to Interfaces and Subinterfaces

The following rules apply to assigning LANE components to the major ATM interface and its subinterfaces:

The assignment of any other component to the major interface is identical to assigning that component to the 0 subinterface.

Example LANE Plan and Worksheet

This section is an example of the LANE plan and worksheet that would be created for the example network configuration described in the "Default Configuration for a Single Emulated LAN" section.

Note   This example configures LANE on the route processor interface (ATM 0), rather than an ATM router module interface. For LANE client configuration examples on ATM router module interfaces, see "Configuring LECs on ATM Router Module Interfaces (Catalyst 8540 MSR)" section.

Figure 13-2 shows the single emulated LAN example network.

The following information describes the LANE plan in Figure 13-2:

Continue with the following sections to start configuring LANE on your ATM network.

Displaying LANE Default Addresses

To make configuration easier, you should display the LANE default addresses for each router or switch router that is running any of the LESs or services and write down the displayed addresses on your worksheet.

To display the default LANE addresses, use the following EXEC command:

Example

The following example displays the default LANE addresses:

Entering the ATM Address of the Configuration Server

You must enter the configuration server ATM address into the ATM switch routers and save it permanently, so that the value is not lost when the device is reset or powered off. The configuration server address can be specified for all of the ATM switch routers, or per port.

To enter the configuration server addresses for all of the ATM switch routers, perform the following steps in global configuration mode:

For examples of these commands, see the "LANE Configuration Examples" section.

Setting Up the Configuration Server Database

After you have determined all LESs, BUSs, and LECS on all ATM subinterfaces on all routers and switch routers that will participate in LANE, and have displayed their ATM addresses, you can use the information to populate the configuration server's database.

You can set up a default emulated LAN, whether or not you set up any other emulated LANs. You can also set up some emulated LANs with restricted membership and others with unrestricted membership.

To set up the LANE database, complete the tasks in the following subsections as appropriate for your emulated LAN plan and scenario. To set up fault-tolerant operation, see the "Configuring Fault-Tolerant Operation" section.

Setting Up the Database for the Default Emulated LAN Only

When you configure a router as the LECS for one default emulated LAN, you provide the following information:

When you set up a database of only a default unrestricted emulated LAN, you do not have to specify where the LANE clients are located. That is, when you set up the configuration servers database for a single default emulated LAN, you do not have to provide any database entries that link the ATM addresses of any clients with the emulated LAN name.

To set up the LECS for the default emulated LAN, perform the following steps, beginning in global configuration mode:

In Step 2, enter the ATM address of the server for the specified emulated LAN, as noted in your worksheet and obtained in the "Displaying LANE Default Addresses" section. You can have any number of servers per emulated LAN for fault tolerance. Entry order determines priority: the first entry has the highest priority unless you override it with the index option.

If you are setting up only a default emulated LAN, the elan-name value in Step 2 is the same as the default emulated LAN name you provide in Step 4.

To set up fault-tolerant operation, see the "Configuring Fault-Tolerant Operation" section.

For examples of these commands, see the "LANE Configuration Examples" section.

Setting Up the Database for Unrestricted-Membership Emulated LANs

When you set up a database for unrestricted emulated LANs, you create database entries that link the name of each emulated LAN to the ATM address of its server.

However, you can choose not to specify the locations of the LANE clients. That is, when you set up the configuration server database, you do not have to provide any database entries that link the ATM addresses or media access control (MAC) addresses of any clients with the emulated LAN name.

To configure a router or switch router as the LECS for multiple emulated LANs with unrestricted membership, perform the following steps, beginning in global configuration mode:

In Steps 2 and 4, enter the ATM address of the server for the specified emulated LAN, as noted in your worksheet and obtained in the "Displaying LANE Default Addresses" section.

To set up fault-tolerant operation, see the "Configuring Fault-Tolerant Operation" section.

For examples of these commands, see the "LANE Configuration Examples" section.

Setting Up the Database for Restricted-Membership Emulated LANs

When you set up the database for restricted-membership emulated LANs, you create database entries that link the name of each emulated LAN to the ATM address of its server. However, you also must specify where the LANE clients are located. That is, for each restricted-membership emulated LAN, you provide a database entry that explicitly links the ATM address or MAC address of each client of that emulated LAN with the name of that emulated LAN.

When clients for the same restricted-membership emulated LAN are located in multiple routers, each client's ATM address or MAC address must be linked explicitly with the name of the emulated LAN. As a result, you must configure as many client entries (See Step 7 in the following procedure) as you have clients for emulated LANs in all the routers. Each client will have a different ATM address in the database entries.

To set up the configuration server for emulated LANs with restricted membership, perform the following steps, beginning in global configuration mode:

To set up fault-tolerant operation, see the "Configuring Fault-Tolerant Operation" section.

Enabling the Configuration Server

After you create the database entries appropriate to the type and to the membership conditions of the emulated LANs, you enable the configuration server on the selected ATM interface, router, or switch router, and specify that the configuration server's ATM address is to be computed automatically.

To enable the configuration server, perform the following steps, beginning in global configuration mode:

For examples of these commands, see the "LANE Configuration Examples" section.

Note   Since the 12.0(1a)W5(5b) release of the system software, addressing the interface on the Catalyst 8510 MSR and LightStream 1010 processor card has changed. The ATM interface is now called atm0, and the Ethernet interface is now called ethernet0. The old formats (atm 2/0/0 and ethernet 2/0/0) are still supported.

Setting Up LESs and Clients

For each device that participates in LANE, set up the necessary servers and clients for each emulated LAN; then display and record the server and client ATM addresses. Be sure to keep track of the router or switch router interface where the LECS will be located.

For one default emulated LAN, you must set up one set of servers: one as a primary server and the rest as backup servers for the same emulated LAN. For multiple emulated LANs, you can set up servers for another emulated LAN on a different subinterface or on the same interface of this router or switch router, or you can place the servers on a different router.

When you set up a server and BUS on a router, you can combine them with a client on the same subinterface, a client on a different subinterface, or no client at all on the router.

Where you put the clients is important, because any router with clients for multiple emulated LANs can route frames between those emulated LANs.

Note   For Token Ring LANE environments that source-route bridge IP traffic to the ATM switch routers, multiring must be configured to enable Routing Information Field (RIF) packets. For an example, see the "Default Configuration for a Token Ring ELAN with IP Source Routing (Catalyst 8510 MSR and LightStream 1010)" section 13-31.

Setting Up the Server, BUS, and a Client on a Subinterface

To set up the server, BUS, and (optionally) clients for an emulated LAN, perform the following steps, beginning in global configuration mode:

If the emulated LAN in Step 2 will have restricted membership, consider carefully whether you want to specify its name here. You will specify the name in the LECS's database when it is set up. However, if you link the client to an emulated LAN, and by some mistake it does not match the database entry linking the client to an emulated LAN, this client will not be allowed to join this or any other emulated LAN.

If you do decide to include the name of the emulated LAN linked to the client in Step 3 and later want to associate that client with a different emulated LAN, make the change in the configuration server's database before you make the change for the client on this subinterface.

Each emulated LAN is a separate subnetwork. In Step 4, make sure that the clients of the same emulated LAN are assigned protocol addresses on the same subnetwork, and that clients of different emulated LANs are assigned protocol addresses on different subnetworks.

For examples of these commands, see the "LANE Configuration Examples" section.

Setting Up a Client on a Subinterface

On any given router or switch router, you can set up one client for one emulated LAN or multiple clients for multiple emulated LANs without a server and BUS. You can set up a client for a given emulated LAN on any routers you select to participate in that emulated LAN. Any router with clients for multiple emulated LANs can route packets among those emulated LANs.

To set up a client for an emulated LAN, perform the following steps, beginning in global configuration mode:

Note   To route traffic between an emulated LAN and a Fast Ethernet (FE) or Gigabit Ethernet (GE) interface, you must configure the LANE client on an ATM router module interface rather than a route processor interface.

Each emulated LAN is a separate subnetwork. In Step 2, make sure that the clients of the same emulated LAN are assigned protocol addresses on the same subnetwork, and that clients of different emulated LANs are assigned protocol addresses on different subnetworks.

Note   For Token Ring LANE environments that source-route bridge IP traffic to the ATM switch routers, multiring must be configured to enable Routing Information Field (RIF) packets. For an example, see the "Default Configuration for a Token Ring ELAN with IP Source Routing (Catalyst 8510 MSR and LightStream 1010)" section.

Example (Catalyst 8540 MSR)

The following example shows how to configure a client for emulated LAN on an ATM router module subinterface:

For additional examples of these commands, see the "LANE Configuration Examples" section.

Configuring a LAN Emulation Client on the ATM Switch Router

This section explains how to configure a LANE client connection from the ATM switch router in the headquarters building to the route processor interface (or optional ATM router module interface on the Catalyst 8540 MSR) of the ATM switch router.

Note   This connection can be used for switch router management only.

A route processor (or optional ATM router module interface) configured as a LANE client allows you to configure the ATM switch router from a remote host.

Configuring an Ethernet LANE Client

To configure the route processor interface (or optional ATM router module interface on the Catalyst 8540 MSR) as an Ethernet LANE client on the ATM switch router, perform the following steps, beginning in global configuration mode:

Note   To route traffic between an emulated LAN and a Fast Ethernet (FE) or Gigabit Ethernet (GE) interface, you must configure the LANE client on an ATM router module interface rather than a route processor interface.

Example

The following example shows how to specify the LANE configuration server (LECS) address and configure a LANE client on the route processor interface to emulate an Ethernet connection using the automatic ATM address assignment:

For additional examples of these commands, see the "LANE Configuration Examples" section. For LANE client configuration examples on ATM router module interfaces, see "Configuring LECs on ATM Router Module Interfaces (Catalyst 8540 MSR)" section.

Configuring Fault-Tolerant Operation

The LANE simple server redundancy feature creates fault tolerance using standard LANE protocols and mechanisms. If a failure occurs on the LECS or on the LES/BUS, the emulated LAN can continue to operate using the services of a backup LES. This protocol is called the Simple Server Redundancy Protocol (SSRP).

For a detailed description of SSRP for LANE, refer to the Guide to ATM Technology.

Enabling Redundant LECSs and LES/BUSs

To enable fault tolerance, you enable multiple, redundant, and standby LECSs and multiple, redundant, and standby LES/BUSs. This allows the connected LANE components to obtain the global list of LECS addresses. Our LANE continues to operate seamlessly with other vendors' LANE components, but fault tolerance is not effective when other vendors' LANE components are present.

To configure multiple LES/BUSs for emulated LANs on the routers or switch routers, perform the following steps, beginning in global configuration mode:

Server redundancy guards against the failure of the hardware on which LES components are running. This includes all the ATM interface cards in our routers and Catalyst switches. Fault tolerance is not effective for ATM network or switch router failures.

Caution   For server redundancy to work correctly, all ATM switch routers must have identical lists of the global LECS addresses, in the identical priority order. The operating LECSs must use exactly the same configuration database.

Load the configuration table data using the configure network command. This method minimizes errors and enables the database to be maintained centrally in one place.

For examples of these commands, see the "LANE Configuration Examples" section.

Implementation Considerations

For important considerations when implementing SSRP, refer to the LANE discussion in the Guide to ATM Technology.

Caution   You can override the LECS address on any subinterface by using the lane auto-config-atm-address, lane fixed-config-atm-address, and lane config-atm-address commands. When you perform an override using one of these commands, however, fault-tolerant operation cannot be guaranteed. To avoid affecting the fault-tolerant operation, do not override any LECS, LES, or BUS addresses.

Monitoring and Maintaining the LANE Components

After configuring LANE components on an interface or any of its subinterfaces, on a specified subinterface, or on an emulated LAN, you can display their status. To show LANE information, use the following EXEC commands:

LANE Configuration Examples

The examples in the following sections illustrate how to configure LANE for the following cases:

All examples use the automatic ATM address assignment method described in the "Automatic ATM Addressing and Address Templates for LANE Components" section.

These examples show the LANE configurations, not the process of determining the ATM addresses and entering them.

Note   For LANE client configuration examples on ATM router module interfaces, see "Configuring LECs on ATM Router Module Interfaces (Catalyst 8540 MSR)" section.

Default Configuration for a Single Emulated LAN

The following examples show how to configure one Cisco 7505 router, one ATM switch, and one Catalyst 5500 switch for a single emulated LAN. Configurations for both Ethernet and Token Ring emulated LANs are shown.

The ATM switch contains the LECS, LES, BUS, and an LEC. The router and Catalyst 5500 switch each contain an LEC for the emulated LAN. This example uses all LANE default settings. For example, it does not explicitly set ATM addresses for the different LANE components that are colocated on the ATM switch. Membership in this emulated LAN is not restricted (see Figure 13-3).

Ethernet Example

ATM Switch