Table of Contents

Cisco's Implementation of SMDS

SMDS Addresses
SMDS Hardware Requirements

SMDS Configuration Task List
Enable SMDS on the Interface

Set SMDS Encapsulation
Specify the SMDS Address
Establish Address Mapping
Map a Multicast Address to an SMDS Address
Enable ARP
Enable Broadcast ARP Messages

Customize Your SMDS Network

Configure Specific Protocols

ARP and IP
DECnet
CLNS
XNS and IPX
AppleTalk
Banyan VINES

Enable Transparent Bridging
Configure SMDS Subinterfaces for Multiple Logical IP Subnetworks
Reenable the Data Exchange Interface Version 3.2 with Heartbeat Support
Configure Pseudobroadcasting
Enable IP Fast Switching

Monitor the SMDS Connection
SMDS Configuration Examples

Typical Multiprotocol Configuration Example
Remote Peer on the Same Network Example
AppleTalk Configuration Examples

Nonextended Appletalk Network Example
Extended AppleTalk Network Example

MultiLIS over SMDS Example
Pseudobroadcasting Example

Configuring SMDS

The Switched Multimegabit Data Service (SMDS) is a wide-area networking service offered by some Regional Bell Operating Companies (RBOCs) and by MCI. This chapter describes the configuration tasks for the SMDS packet-switched software. For a complete description of the commands mentioned in this chapter, refer to the "SMDS Commands" chapter in the Router Products Command Reference publication. For historical background and a technical overview of SMDS, see the Internetworking Technology Overview publication.

Cisco's Implementation of SMDS

Cisco's implementation of the SMDS protocol is based on cell relay technology as defined in the Bellcore Technical advisories, which are based on the IEEE 802.6 standard. We provide an interface to an SMDS network using DS-1 or DS-3 high-speed transmission facilities. Connection to the network is made through a device called an SDSU—an SMDS Channel Service Unit/Digital Service Unit (CSU/DSU) developed jointly by Cisco Systems and Kentrox. The SDSU attaches to a Cisco router through a serial port. On the other side, the SDSU terminates the line.

Cisco's implementation of SMDS supports the IP, DECnet, AppleTalk, XNS, Novell IPX, Banyan VINES, and OSI internetworking protocols, and transparent bridging.

Routing of AppleTalk, DECnet, IP, and ISO CLNS is fully dynamic; that is, the routing tables are determined and updated dynamically. Routing of the other supported protocols requires that you establish a static routing table of SMDS neighbors in a user group. Once this is set up, all interconnected routers provide dynamic routing.

Cisco's SMDS implementation includes multiple logical IP subnet (MultiLIS) support as defined by RFC 1209. This RFC describes routing IP over an SMDS cloud where each connection is considered a host on one specific private network and points to cases where traffic must transit from network to network.

Cisco's implementation of SMDS also provides the Data Exchange Interface (DXI) Version 3.2 with heartbeat. The heartbeat mechanism periodically generates a heartbeat poll frame.

When a multicast address is not available to a destination, pseudobroadcasting can be enabled to broadcast packets to those destinations using a unicast address.

SMDS Addresses

All addresses for SMDS service are assigned by the service provider and can be assigned to individuals and groups.

SMDS Hardware Requirements

You need the following hardware, equipment, and special software to configure SMDS:

• CSC-MCI or CSC-SCI serial interface controller card, or HSSI interface (chassis-based systems), or the serial port on an IGS router.
  
  

  To operate on CSC-SCI or CSC-MCI cards, SMDS requires that the appropriate microcode version be installed. Version numbers are 1.2 (or later) for CSC-SCI and 1.7 (or later) for CSC-MCI.

• SDSU device.
  
  
• Packet-switched software option with the system software.
  
  

Figure 11-1 illustrates the connections between the different components.

SMDS Configuration Task List

Before you can begin the configuration tasks, you must have already obtained your SMDS addresses from your service provider. You need two types of addresses:

• The group address for broadcasts
  
  
• The SMDS hardware (individual) address for each router that will interface directly into the SMDS network (that is, customer premises equipment).
  
  

There are basic steps that you must perform to enable SMDS. In addition, you can customize SMDS for your particular network needs and monitor SMDS connections. Perform the tasks in the following sections:

• Enable SMDS on the Interface
  
  
• Customize Your SMDS Network
  
  
• Monitor the SMDS Connection
  
  

See the examples at the end of this chapter for ideas of how to configure SMDS on your network.

Enable SMDS on the Interface

You must perform the tasks in the following sections to enable SMDS:

• Set SMDS Encapsulation
  
  
• Specify the SMDS Address
  
  
• Establish Address Mapping
  
  
• Map a Multicast Address to an SMDS Address
  
  
• Enable ARP
  
  
• Enable Broadcast ARP Messages
  
  

Set SMDS Encapsulation

To set SMDS encapsulation at the interface level, perform the following task in interface configuration mode:

For examples of enabling SMDS encapsulation, see any of the examples in the section "SMDS Configuration Examples" later in this chapter.

Specify the SMDS Address

To specify the SMDS individual address for a particular interface, perform the following task in interface configuration mode:

Establish Address Mapping

Routing tables are configured dynamically when AppleTalk Phase II, DECnet, IP, and ISO CLNS routing are configured. However, you can configure static mapping for these protocols, if needed. For any other protocol, you must configure a static map between an individual SMDS address and a higher-level protocol address. To establish address mapping, perform the following task in interface configuration mode:

The supported protocols and the keywords to enable them are as follows:

• AppleTalk—appletalk
  
  
• Banyan VINES—vines
  
  
• DECnet—decnet
  
  
• IP—ip
  
  
• ISO CLNS—clns
  
  
• Novell IPX—ipx
  
  
• XNS—xns
  
  

For examples of establishing address mapping, see any of the examples in the section "SMDS Configuration Examples" later in this chapter.

Map a Multicast Address to an SMDS Address

You can map an SMDS group address to a broadcast or multicast address used by a higher-level protocol. If you map an SMDS group address to a broadcast or multicast address used by higher-level protocol, the broadcast keyword does not need to be specified in the smds static-map command, and the router will not need to replicate each broadcast address.

• AppleTalk—appletalk
  
  
• AppleTalk ARP address—aarp
  
  
• Banyan VINES—vines
  
  
• Bridging—bridge
  
  
• DECnet—decnet
  
  
• DECnet multicast address for all Level 1 routers—decnet_router-L1
  
  
• DECnet multicast address for all Level 2 routers—decnet_router-L2
  
  
• DECnet multicast address for all end systems—decnet_node
  
  
• IP—ip
  
  
• ISO CLNS—clns
  
  
• Multicast address for all CLNS intermediate systems—clns_is
  
  
• Multicast address for all CLNS end systems—clns_es
  
  
• Novell IPX—ipx
  
  
• XNS—xns
  
  

Enable ARP

When you enable the Address Resolution Protocol (ARP), you can choose to enable either a dynamic ARP cache or one built statically. To enable ARP, perform one of the following tasks in global configuration mode:

An SMDS network can be thought of in much the same way as an X.25 cloud. The premises equipment (in this case our router) represents the edge of the cloud. The service provider enables communication across the cloud. However, proper configuration is needed for communication to occur. This configuration will differ between protocol families.

Enable Broadcast ARP Messages

When an ARP server is present in the network, you can enable broadcast ARP messages that are sent to all ARP SMDS addresses or to all IP SMDS multicast addresses when ARP addresses are not present. To enable broadcast ARP messages, perform the following task in interface configuration mode:

Customize Your SMDS Network

Perform the tasks in the following sections, as appropriate, for your network:

• Configure Specific Protocols
  
  
• Enable Transparent Bridging
  
  
• Configure SMDS Subinterfaces for Multiple Logical IP Subnetworks
  
  
• Reenable the Data Exchange Interface Version 3.2 with Heartbeat Support
  
  
• Configure Pseudobroadcasting
  
  
• Enable IP Fast Switching
  
  

Configure Specific Protocols

Some protocol families are dynamically routed. For IP and CLNS, routing is fully dynamic, and no action on your part is needed to map higher-level protocol addresses to SMDS addresses. But for the other supported protocols, you must make a static entry for each router to communicate with all other peer routers. The static entries only need to be made for those routers that are SMDS remote peers. Nothing additional needs to be done to assure communication with other nodes behind the peer routers.

For an example of how to configure specific protocols, see the section "Typical Multiprotocol Configuration Example" later in this chapter.

Table 11-1 lists protocol families and the multicasts that are needed.

ARP and IP

For both IP and ARP, the multicast address must be configured and ARP must be enabled. ARP multicast is required for only ARP servers; the IP multicast is used for ARPs and routing updates.

DECnet

Static maps must be configured for DECnet. In addition, a separate smds multicast command is needed for DECNET, DECNET_NODE, DECNET_ROUTER-L1, and DECNET_ROUTER-L2.

CLNS

Multicasts must be configured for CLNS_ES and CLNS_IS. No static maps are necessary. ESHs, ISHs, and Router hello packets are sent to the multicast address, and neighbor entries are created automatically.

XNS and IPX

For XNS and IPX, the multicast address must be configured.

AppleTalk

The SMDS cloud must be treated by all AppleTalk routers connected to it as either extended or nonextended. The network types cannot be mixed on the same SMDS cloud. Instead, all AppleTalk routers on an SMDS cloud must agree about the network type: extended or nonextended.

If any router in the SMDS cloud uses Cisco IOS Release 10.3(3) (or earlier), use a nonextended AppleTalk configuration for the SMDS cloud. To use nonextended AppleTalk, use the appletalk address command and configure static maps.

If all routers in the SMDS cloud use Cisco IOS Release 10.3(4) (or later), you can use extended AppleTalk to support dynamic AARP for SMDS addresses. To use extended AppleTalk, use the appletalk cable-range command.

For an example of how to configure AppleTalk, see the section "AppleTalk Configuration Examples" later in this chapter.

Banyan VINES

For Banyan VINES, the multicast address must be configured. Also note that VINES only works with static maps.

Enable Transparent Bridging

You can enable transparent bridging of packets across an SMDS network. The first step is to assign the interface to the bridge group using the bridge-group command. To enable transparent bridging, perform the following task in interface configuration mode:

Configure SMDS Subinterfaces for Multiple Logical IP Subnetworks

Multiple logical IP subnets (MultiLIS) are supported as defined by RFC 1209. This RFC describes routing IP over an SMDS cloud where each connection is considered a host on one specific private network and describes cases where traffic must transit from network to network.

The MultiLIS solution allows a single SMDS interface to be treated as multiple logical IP subnets and to support routing of packets from one network to the next without using intervening routers. When MultiLIS is enabled, the router performs routing between the subnets using IP addresses on an SMDS interface. Each supported subnet has an IP address, a unicast SMDS E.164 address, and a multicast SMDS E.164 address configured on the SMDS interface. Broadcast packets are duplicated and transmitted to all IP networks on the specified SMDS interface and use the associated multicast SMDS address for the network.

To configure a router to have multipoint subinterfaces for multiple logical IP subnets, perform the following tasks in interface configuration mode:

For an example of how to configure MultiLIS, see the "MultiLIS over SMDS Example" section later in this chapter.

Reenable the Data Exchange Interface Version 3.2 with Heartbeat Support

By default, SMDS provides the Data Exchange Interface (DXI) Version 3.2 heartbeat process as specified in the SIG-TS-001/1991 standard. If you find you must reenable the DXI heartbeat, perform the following task in interface configuration mode:

Configure Pseudobroadcasting

Some hosts do not support multicast E.164 addresses. This is a problem in IP where frequent broadcast packets are sent, because routing updates are generally broadcast. IP and ARP depend on the use of multicast addresses to determine a route to a destination IP address. A mechanism was needed to artificially support the use of broadcast where multicast E.164 addresses do not exist; the result is that a multicast address is not available to a destination, pseudobroadcasting can be enabled to broadcast packets to those destinations using a unicast address.

Enable IP Fast Switching

SMDS fast switching of IP packets provides faster packet transfer on serial links with speeds above 56 Kbps. Use fast switching if you use high-speed, packet-switched, datagram-based WAN technologies such as Frame Relay offered by service providers.

By default, SMDS fast switching is enabled.

To reenable fast switching, perform the following tasks.

Monitor the SMDS Connection

To monitor the SMDS connection, perform one or more of the following tasks in EXEC mode:

SMDS Configuration Examples

The following section provides typical configuration file examples you can use as models for your network configurations:

• Typical Multiprotocol Configuration Example
  
  
• Remote Peer on the Same Network Example
  
  
• AppleTalk Configuration Examples
  
  
• MultiLIS over SMDS Example
  
  
• Pseudobroadcasting Example
  
  

Typical Multiprotocol Configuration Example

The following example is a typical interface configured for IP, DECnet, ISO CLNS, Novell IPX, XNS, and AppleTalk. DECnet needs to be configured globally and at the interface level.

Remote Peer on the Same Network Example

The following example illustrates a remote peer on the same SMDS network. DECnet needs to be configured globally and at the interface level.

AppleTalk Configuration Examples

The following two sections provide basic examples of configuration for a nonextended AppleTalk network and for an extended AppleTalk network.

Nonextended Appletalk Network Example

The following example configures SMDS for a nonextended AppleTalk network. When SMDS is configured for a nonextended AppleTalk network, SMDS static maps are required. Dynamic AppleTalk Address Resolution Protocol (AARP) is not supported on the multicast channel.

Extended AppleTalk Network Example

If all AppleTalk routers on the SMDS cloud are running Release 10.2(6) or 10.3(3) software or newer, you can use an AppleTalk extended network. This is done using the appletalk cable-range interface command.

When SMDS is configured for an extended AppleTalk network, SMDS static maps are not required and not used. Dynamic AARP is supported on the multicast channel.

MultiLIS over SMDS Example

In the following example, Routers A, B, and C are connected to an SMDS cloud (see Figure 11-2).

Router A knows about two IP networks and can communicate with Routers B and C directly. Router B can communicate with Router A directly, and with Router C via Router A. Router C can communicate with Router A directly and with Router B via Router A. Notice that a packet destined to Router B from Router C must make two hops on the cloud through the same interface on Router A. This issue was considered when the MultiLIS proposal was made and deemed not to be a critical one. It is also a nonstandard configuration.

Pseudobroadcasting Example

In the following example, an ARP broadcast from Router A is sent to multicast address E180.0999.9999.FFFF to Router B and to unicast address C120.1234.5678.FFFF to Router C. The reply from Router C uses the unicast address C120.1111.2222.FFFF for the return reply if it is the target of the ARP request. IGRP broadcast updates follow the same rules.

Configuration for Router A

Configuration for Router B

Configuration for Router C

Posted: Mon Oct 21 11:12:24 PDT 2002
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