ATM is a cell-switching and multiplexing technology that combines the benefits of circuit switching (constant transmission delay and guaranteed capacity) with those of packet switching (flexibility and efficiency for intermittent traffic). Like X.25 and Frame Relay, ATM defines the interface between the user equipment (such as workstations and routers) and the network (referred to as the User-Network Interface [UNI]).

Token Ring LANE allows Token Ring LAN users to take advantage of the benefits of ATM without modifying end-station hardware or software. ATM uses connection-oriented service with point-to-point signalling or multicast signalling between source and destination devices. However, Token Ring LANs use connectionless service. Messages are broadcast to all devices on the network. With Token Ring LANE, routers and switches emulate the connectionless service of a Token Ring LAN for the end stations.

By using Token Ring LANE, you can scale your networks to larger sizes while preserving your investment in LAN technology.

Note	The Catalyst 5000 series Cisco IOS Token Ring LANE software does not support Ethernet LANE or RFC 1483 permanent virtual connections (PVCs).

LANE defines emulated LANs (ELANs). An ELAN consists of the following components:

• LANE client (LEC)--A LEC emulates a LAN interface to higher-layer protocols and applications. It forwards data to other LANE components and performs LANE address resolution functions. Each LEC is a member of only one ELAN. However, a switch or a Catalyst ATM module can include LECs for multiple ELANs; there is one LEC for each ELAN of which it is a member.

If a switch has LECs for multiple ELANs, the switch can route traffic between ELANs.

• LANE server (LES)--The LES is the control center for an ELAN. It provides joining, address resolution, and address registration services to the LECs in that ELAN. LECs can register destination unicast and multicast MAC address with the LES. The LES also handles LANE Address Resolution Protocol (LE_ARP) requests and responses and maintains a list of route descriptors that is used to support source-route bridging (SRB) over ELANs. The route descriptors are used to determine the ATM address of the next hop in the frame’s routing information field (RIF).

There is one LES per ELAN.

• LANE broadcast and unknown server (BUS)--The BUS floods unknown destination traffic and forwards multicast and broadcast traffic to LECs within an ELAN.

One combined LES and BUS is required for each ELAN.

• LANE Configuration Server (LECS)--The LECS contains the database that determines which ELAN a device belongs to (each LECS can have a different database). Each LEC contacts the LECS once to determine which ELAN it should join. The LECS returns the ATM address of the LES for that ELAN.

One LECS is required for each ATM LANE switch cloud.

The LECS database can have the following types of entries:

• • ELAN name, ATM address of LES pairs
  • ELAN name and the ring number of the ELAN (local-seg-id)
  • LEC MAC address, ELAN name pairs
  • LEC ATM template, ELAN name pairs
  • Default ELAN name

Note	An ELAN name must be unique on an interface. If two interfaces participate in LANE, the second interface may be in a different switch cloud.

The server assigns individual LECs to particular ELANs by directing them to the LES for the ELAN. The LECS maintains a database of LEC and server ATM or MAC addresses and their ELANs. A LECS can serve multiple ELANs.

• Fast Simple Server Redundancy Protocol (FSSRP)--Token Ring LANE relies on three servers: LECS, LES, and BUS. If any one of these servers fails, the ELAN cannot fully function.

Cisco has developed a fault tolerant mechanism known as Simple Server Redundancy Protocol (SSRP) that eliminates these single points of failure. Although there is only one LES per ELAN, SSRP allows you to configure redundant servers. You can configure servers to act as backup servers that become active if a master server fails. The priority levels for the servers determine which servers have precedence.

FSSRP is an enhancement to the SSRP. With FSSRP, LECs no longer need to go down whenever there is a change in the master LES. This uninterrupted service is achieved by connecting the LECs simultaneously to more than one LES/BUS (up to four) so that if the master LES goes down, the backup LESs are immediately available. With the basic SSRP, the LEC must go down and completely recycle before coming back up. This operation is accomplished by keeping the control connections open to all of the active LESs and BUSs in the ELAN. Although this method uses more virtual circuits (VCs), the main benefits are the transparency and speed in the switchover.

Note	ELAN components coexist on one or more Cisco routers or Catalyst switches that contain an ATM module. On Cisco routers or Catalyst switches the LES and the BUS are combined into a single entity.

Use the session mod_num line configuration command to open a session to the ATM module from the Catalyst 5000 family switch in which the module is installed.

This example shows how to create a session to an ATM module installed in slot 5 of the Catalyst 5000 switch:

Console> (enable) session 5
Trying ATM-5...
Connected to ATM-5.
Escape character is '^]'.

ATM>

After opening the session, you see the ATM> prompt. You then have direct access only to the ATM module with which you have established a session.

Note	The ATM module uses a subset of Cisco IOS software. Generally, Cisco IOS software works the same on the ATM module as it does on routers.

To configure the ATM module, you must use the ATM configuration mode in the Cisco IOS software. To enter global configuration mode, enter the configure EXEC command at the privileged EXEC prompt (ATM#). You see the following message, which asks you to specify the terminal, the NVRAM, or a file stored on a network server as the source of configuration commands:

Configuring from terminal, memory, or network [terminal]?

If you specify terminal, the run-time configuration is used. You can then save the run-time configuration into the NVRAM. If you specify memory, the run-time configuration is updated from the NVRAM. If you specify network, the run-time configuration is updated from a file in a server on the network.

Note	You cannot configure from the network.

The ATM module accepts one configuration command per line. You can enter as many configuration commands as you want.

You can add comments to a configuration file describing the commands you have entered. Precede a comment with an exclamation point (!) or pound sign (#). Comments are not stored in NVRAM or in the active copy of the configuration file. In other words, comments do not appear when you list the active configuration with the write terminal EXEC command or list the configuration in NVRAM with the show configuration EXEC command. Comments are stripped out of the configuration file when it is loaded to the ATM module.

Before you begin to configure Token Ring LANE, you must decide whether you want to set up one or multiple ELANs. If you set up multiple ELANs, you must also decide where the servers and LECs will be located, and whether to restrict the clients that can belong to each ELAN. Bridged ELANs are configured just like any other LAN, in terms of commands and outputs. Once you have made those decisions, you can configure Token Ring LANE.

Before implementing Token Ring LANE, it might help you to begin by drawing up a plan and a worksheet for your own LANE scenario, showing the following information and leaving space to note the ATM address of each LANE component on each subinterface for each participating switch:

• Catalyst 5000 series switch interface where the LECS will be located.

• Catalyst 5000 series switch interface and subinterface where the LES/BUS for each ELAN will be located. For fault-tolerant operation, multiple servers can be on each ELAN.

• Catalyst 5000 series switch ATM modules, subinterfaces, and VLANs where the LECs for each ELAN will be located.

• Name of the default ELAN (optional). The default Token Ring ELAN is the same as the default TrCRF (1003). You can use the default Token Ring ELAN (trcrf-default) or configure a new one.

• Names of the ELANs that will have unrestricted membership.

• Names of the ELANs that will have restricted membership.

• Local segment ID for the ELAN. The local segment ID must be identical to the ring number of the TrCRF.

Note	The last three items in the list above are important because they determine how you set up each ELAN in the LECS database.

1.    ATM# configure terminal

2.    ATM(config)# interface atm>elanname

3.    ATM(config-if)# lane client tokenring>elanname

4.    ATM(config-if)# Ctrl-Z

5.    ATM(config)# write memory

In the following example, the ATM module is configured from the terminal. The interface atm 0 interface configuration command designates that ATM interface 0 is to be configured. The lane client tokenring command links TrCRF 10 to the ELAN named trcrf-10. The Ctrl-Z command quits configuration mode. The write memory command loads the configuration changes into NVRAM on the ATM module.

ATM# configure terminal
ATM (config)# interface atm 0
ATM (config-subif)# lane client tokenring 10 trcrf-10
ATM (config-subif)# Ctrl-Z
ATM# write memory

NVRAM stores the current configuration information in text format as configuration commands, recording only nondefault settings. The ATM module software performs a memory checksum to guard against corrupted data.

As part of its startup sequence, the ATM module startup software always checks for configuration information in NVRAM. If NVRAM holds valid configuration commands, the ATM module executes the commands automatically at startup. If the ATM module detects a problem with its NVRAM or the configuration it contains, the module goes into default configuration. Problems can include a bad checksum for the information in NVRAM or the absence of critical configuration information.

To configure the ATM module from NVRAM, reexecute the configuration commands in privileged EXEC mode:

ATM(config)# configure memory

Before you configure LANE components on a Catalyst 5000 series switch ATM module, you must configure the Cisco LightStream 1010 switch with the ATM address prefix to be used by all LANE components in the switch cloud.

Note	On the Cisco LightStream 1010 switch, the ATM address prefix is called the node ID. Prefixes must be 26 digits long. If you provide fewer than 26 digits, zeros are added to the right of the specified value to fill it to 26 digits. LANE prefixes must start with 39 or 47.

Note	If you do not save the configured value permanently, it will be lost when the switch is reset or powered off.

To display the current prefix on the Cisco LightStream 1010 switch, use the show network EXEC command.

To set the ATM address prefix, use the following commands on the Cisco LightStream 1010 switch beginning in global configuration mode:

1.    Switch(config)# atm address {atm_address | prefix... }

2.    Switch(config)# exit

3.    Switch# copy running-config startup-config

1.    ATM(config)# interface atmslot/port

2.    ATM(config)# atm pvcvcd vpi vci qsaal

3.    ATM(config)# atm pvcvcd vpi vciilmi

You can display the LANE default addresses to make configuration easier. Complete this task for each router that participates in LANE. This command displays default addresses for all ATM interfaces present on the router. Write down the displayed addresses on your worksheet.

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

Router# show lane default-atm-addresses

1.    Switch(config)# atm lecs-address-default address1 [address2... ]

2.    Router(config)# exit

3.    Switch# copy running-config startup-config

The LECS database contains LANE configuration information, including ELAN name-to-LES/BUS ATM address mappings, LEC address-to-ELAN name mappings, and the name of the default ELAN, if specified. You must configure at least one LECS database in the LANE network.

When configuring the LECS database, remember the following guidelines:

• You can configure redundant LECSs. Redundant LECSs should be configured on different devices in the LANE network. If you configure more than one LECS, make sure that all databases with the same name are identical.

• You can specify one default ELAN in the database. The LECS assigns any client that does not request a specific ELAN to the default ELAN.

• ELANs are either restricted or unrestricted. The LECS assigns a client to an unrestricted ELAN if the client specifies that particular ELAN in its configuration. However, the LECS only assigns a client to a restricted ELAN if the client is specified in the LECS’s database as belonging to that ELAN. The default ELAN should have unrestricted membership.

• If you are configuring fault tolerance, you can have any number of servers per ELAN. Priority is determined by entry order; the first entry has the highest priority unless you override it with the index option.

When setting up the LECS database remember that the following are requirements when configuring LECs:

• The VLAN name must match the ELAN name.

• The ring number defined when configuring the VLAN must match the local segment ID.

The set vlan interface configuration command assumes that any ring number you enter is in hexadecimal. Therefore, 12 is stored as the hexadecimal value 0x12. The name elan_name local-seg-id segment_numberLANE database configuration command assumes that any value you enter for the local-seg-id is in decimal unless you enter it explicitly in hexadecimal. For example, to define a TrCRF with a ring number of 12 you could enter the set vlan 12 name crf12 type trcrf ring 12 parent 100 interface configuration command or the set vlan 12 name crf12 type trcrf ring 0x12 parent 100 interface configuration command.

When defining a corresponding LEC, you could enter the name crf12 local-seg-id 0x12 or name crf12 local-seg-id 18 LANE database configuration command because 18 is the decimal equivalent of 0x12.

To set up the database, complete the tasks in the following sections as appropriate for your ELAN plan and scenario:

1.    ATM(config)# interface atmnumber

2.    ATM(config-if)# lane config auto-config-atm-address

3.    ATM(config-if)# lane config databasedatabase-name

4.    ATM(config-if)# exit

5.    ATM# copy running-config startup-config

For each Catalyst 5000 series switch ATM module that will participate in LANE, set up the necessary servers and clients for each ELAN and then display and record the server and client ATM addresses. Be sure to keep track of the switch ATM interface where the LECS will eventually be located.

If you will have only one default ELAN, you only need to set up one server. If you will have multiple ELANs, you can set up the server for another ELAN on a different subinterface on the same interface of this switch, or you can place it on a different switch.

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

Depending on where your clients and servers are located, perform one of the following tasks for each LANE subinterface:

The LANE protocol does not specify where any of the ELAN server entities should be located, but for the purpose of reliability and performance, Cisco implements these server components on its routers and LAN switches.

With Phase I LANE, only one LECS, capable of serving multiple ELANs, and only one LES per ELAN could exist for an ATM cloud. The Phase I LANE protocol did not allow for multiple LESs within an ELAN. Therefore, these components represented both single points of failure and potential bottlenecks for LANE service.

LANE LES/BUS and LECS redundancy corrects these limitations by allowing you to configure redundant LES/BUSs so that the LECs in an ELAN can automatically switch to a backup LES if the primary LES fails. The priority of the LES/BUS pairs is established by the order in which they are entered in the LECS database. LANE LES/BUS and LECS redundancy is always enabled. You can use this redundancy feature by configuring multiple servers.

LES/BUS and LECS redundancy works only with Cisco LECS and LES combinations. Third-party LANE server components continue to interoperate with the LECS and LES/BUS function of Cisco routers and switches, but cannot take advantage of the redundancy features.

The following servers are single points of failure in the ATM LANE system:

• LECS (configuration server)

• LES (ELAN server)

• BUS

LES/BUS and LECS redundancy eliminates these single points of failure.

Once you have set up the LECs on the subinterfaces of an ATM module, you can display their ATM addresses by using the following command in privileged EXEC mode:

Router# show lane

The command output shows all the subinterfaces configured for LANE. For each subinterface, the command displays and labels the ATM addresses that belong to the LES, BUS, and the LEC.

When you look at each ATM address, confirm the following items:

• The prefix is the one you set up on the switch.

• The end-system identifier field reflects the base address of the pool of MAC addresses assigned to the ATM interface plus a value that represents the specific LANE component.

• The selector byte is the same number as the subinterface (converted to hexadecimal).

Enter the show lane EXEC command on each Catalyst 5000 series switch to verify the LANE setup before you set up the LECs on the next Catalyst 5000 series switch. Print the display or make a note of these ATM addresses so that you can use it when you set up the LECS database. At this point in the configuration process, the LECs are not normally operational.

After configuring LANE components on an interface or any of its subinterfaces, you can display their status on a specified subinterface or on an ELAN. To show LANE information, issue the following commands in privileged EXEC mode:

Router# show lane [interface atm 0 [subinterface-number
 | name elan-name
]] [brief]

Router# show lane bus [interface atm 0 [subinterface-number
] | name elan-name
] [brief]

Router# show lane client [interface atm 0 [subinterface-number
] | name elan-name
] [brief]

Router# show lane config [interface atm 0]

Router# show lane database [database-name
]

Router# show lane le-arp [interface atm 0 [subinterface-number
] | name elan-name
]

Router# show lane server [interface atm 0 [subinterface-number
] | name elan-name
] [brief]

Note	For descriptions of the output displayed by the commands listed above, see the description of the command documented in the Cisco IOS Switching Services Command Reference .

For the example in the "Token Ring LANE Configuration Example," the following assumptions apply:

• Catalyst 5000 series switches with the ATM modules installed are running ATM software Release 4.9b or later.

• Catalyst 5000 series switch 1 runs the LES/BUS and LECS on interface atm0 and the LEC on interface atm0.1.

• Catalyst 5000 series switch 2 runs LEC on interface atm0.1.

• The ATM module is installed in slot 4 of both Catalyst 5000 series switches.

• You can change the ELAN name by entering the set vlan vlan_num [name vlan_name] command.

• The ELAN on the switches is essentially a new TrCRF. The ELAN name is crf112 and the VLAN ID is 112.

• The parent TrBRF to the TrCRF 112 is brf400 (VLAN ID 400).

1.    At the enable prompt, enter the following command:

2.    To verify the configuration of the new VLAN, enter the show vlancommand.

Console> (enable) set vlan 112 name crf112 type trcrf ring 112 parent 400 mode srb

Console> (enable) show vlan 112
VLAN Name                             Status    Mod/Ports, Vlans
---- -------------------------------- --------- ----------------------------
112  crf112                           active
VLAN Type  SAID       MTU   Parent RingNo BrdgNo Stp  BrdgMode Trans1 Trans2
---- ----- ---------- ----- ------ ------ ------ ---- -------- ------ ------
112  trcrf 100112     4472  400    0x112  -      -    srb      0      0
VLAN AREHops STEHops Backup CRF
---- ------- ------- ----------
112  7       7       off
Console> (enable)

1.    Set up the prefix of the ATM NSAP address for the switch.

2.    Start a session to the ATM module by entering the session 4 interface configuration command. You see the following display:

3.    Obtain the addresses of the LES/BUS for later use by entering the enable router configuration command (to enable configuration mode) and the show lane default-atm-addresses EXEC command at the ATM prompt. You see the following display:

4.    Using the LECS address obtained in Step 3, set the address of the default LECS in the LightStream 1010 switch by entering the configure terminal and atm lecs-address-default commands on the console of the LightStream 1010 switch. You see the following display:

5.    Save the configuration to NVRAM by entering the write memory command, as follows:

6.    Start a LES/BUS pair on Catalyst 5000 series switch 1 by entering the interface atm0 and the lane server-bus tokenring commands in global configuration mode. On the console of Catalyst 5000 series switch 1, enter the following commands:

7.    Save the configuration in NVRAM entering the write memory command, as follows:

8.    Set up the LECS database on the Catalyst 5000 series switch 1.

9.    Save the configuration in NVRAM by entering the write memory command, as follows:

10.    Start and bind the LECS on the Catalyst 5000 series switch 1 by entering the interface atm0, the lane config database database_name interface configuration command, and the lane config auto-config-atm-address interface configuration commands at the ATM prompt. You see the following display:

11.    Save the configuration in NVRAM by entering the write memory command, as follows:

12.    Start the LEC on the Catalyst 5000 series switches 1 and 2 by entering the interface atm0.1 command and the lane client tokenring 112 crf112 interface configuration command in configuration mode on the consoles of switches 1 and 2. The interface on which the LEC is configured is atm0.1. The ELAN name is default, and it is configured to emulate Token Ring. You see the following display:

13.    Save the configuration in NVRAM by entering the write memory command, as follows:

Console> session 4
Trying ATM-4...
Connected to ATM-4.
Escape character is '^]'.
ATM>

ATM> enable
ATM#
ATM# show lane default-atm-addresses interface atm0
interface ATM0:
LANE Client:        47.0091810000000061705b7701.00400BFF0010.**
LANE Server:        47.0091810000000061705b7701.00400BFF0011.**
LANE Bus:           47.0091810000000061705b7701.00400BFF0012.**
LANE Config Server: 47.0091810000000061705b7701.00400BFF0013.00
ATM#

Switch> enable
Switch#
Switch# configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Switch(config)# atm lecs-address-default 47.0091810000000061705b7701.00400BFF0013.00 1
Switch(config)# end
Switch#

ATM# write memory

ATM# configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
ATM(config)# interface atm0
ATM(config-subif)# lane server-bus tokenring crf112
ATM(config-subif)# end
ATM#

ATM# write memory

ATM# config terminal
Enter configuration commands, one per line.  End with CNTL/Z.
ATM(config)# lane database test
ATM(lane-config-database)# name trcf-default server-atm-address
                             47.0091810000000061705b7701.00400BFF0011.00
ATM (lane-config-database) name crf112 local-seg-id 0x112
ATM(lane-config-database)# default-name crf112
ATM(lane-config-database)# exit
ATM#

ATM# write memory

ATM# configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
ATM(config)# interface atm0
ATM(config-if)# lane config database test
ATM(config-if)# lane config auto-config-atm-address
ATM(config-if)# end
ATM#

ATM# write memory

ATM# configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
ATM(config)# interface atm0.1
ATM(config-subif)# lane client tokenring 112 crf112
ATM(config-subif)# end
ATM#

ATM# write memory