Cisco IOS Wide-Area Networking Configuration Guide, Release 12.4T
Configuring SMDS
Downloads: This chapterpdf (PDF - 228.0KB) The complete bookPDF (PDF - 6.69MB) | Feedback

Configuring SMDS

Table Of Contents

Configuring SMDS

Finding Feature Information

Contents

Prerequisites for SMDS

Information About SMDS

SMDS Hardware Requirements

SMDS Addresses

Customizing the SMDS Network

Configuring Specific Protocols

Transparent Bridging over SMDS

SMDS Subinterfaces for Multiple Logical IP Subnetworks

Reenabling Data Exchange Interface Version 3.2 with Heartbeat Support

Pseudobroadcasting

Fast Switching

SMDS Configuration Task List

Enabling SMDS on the Interface

Setting SMDS Encapsulation

Specifying the SMDS Address

Establishing Address Mapping

Mapping a Multicast Address to an SMDS Address

Enabling ARP

Enabling Broadcast ARP Messages

Enabling Dynamic Address Mapping for IPX over SMDS

Customizing Your SMDS Network

Enabling Transparent Bridging over SMDS

Configuring SMDS Subinterfaces for Multiple Logical IP Subnetworks

Reenabling Data Exchange Interface Version 3.2 with Heartbeat Support

Configuring Pseudobroadcasting

Enabling Fast Switching

Monitoring the SMDS Connection

SMDS Configuration Examples

Typical Multiprotocol Configuration Example

Remote Peer on the Same Network Example

IPX Dynamic Address Mapping Example

AppleTalk Configuration Examples

Extended AppleTalk Network Example

Nonextended Appletalk Network Example

Multiple Logical IP Subnetworks over SMDS Example

Pseudobroadcasting Example

Feature Information for SMDS


Configuring SMDS


Last Updated: August 16, 2010

The Switched Multimegabit Data Service (SMDS) is a WAN service offered by a variety of service providers.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the "Feature Information for SMDS" section.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Contents

Information About SMDS

Prerequisites for SMDS

SMDS Configuration Task List

SMDS Configuration Examples

Feature Information for SMDS

Prerequisites for SMDS

You must have already obtained your SMDS addresses from your service provider. You need the following two types of addresses:

The group address for broadcasts

The SMDS hardware (individual) address for each router that interfaces directly into the SMDS network (that is, customer premises equipment)

Information About SMDS

SMDS Hardware Requirements

SMDS Addresses

Customizing the SMDS Network

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 a HSSI interface on chassis-based systems, or the serial port on a 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.

EIA/TIA-449 or V.35 applique

SMDS data service unit (SDSU) device

Figure 1 illustrates the connections among the components.

Figure 1 Typical SMDS Configuration

SMDS Addresses

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

You must enter addresses in the Cisco SMDS configuration software using an E prefix for multicast addresses and a C prefix for unicast addresses.

Cisco IOS software expects the addresses to be entered in E.164 format, which is 64 bits (15-digit addressing). The first 4 bits are the address type, and the remaining 60 bits are the address. If the first 4 bits are 1100 (0xC), the address is a unicast SMDS address, which is the address of an individual SMDS host. If the first 4 bits are 1110 (0xE), the address is a multicast SMDS address, which is used to broadcast a packet to multiple end points. The 60 bits of the address are in binary-coded decimal (BCD) format. Each 4 bits of the address field presents a single telephone number digit, allowing for up to 15 digits. At a minimum, you must specify at least 11 digits (44 bits). Unused bits at the end of this field are filled with ones.


Note The arp smds command supports 48-bit addresses only (C or E followed by 11 digits). The addresses must be entered in dotted notation—for example, C141.5556.1414.


An example of a 15-digit E.164 address follows:

C14155561313FFFF

Note Older versions of Cisco IOS software supported 48-bit SMDS addresses. If, when using the current version of the software, you write the configuration to NVRAM, the full 64-bit SMDS address is written. Older versions of the software will no longer be able to read the new SMDS configuration from NVRAM. However, the current version of the software can read previous versions of the configuration in NVRAM.


The addresses can be entered with periods in a manner similar to Ethernet-style notation, or simply as a string of digits.

The following is an example of an individual address entered in Ethernet-style notation:

C141.5555.1212.FFFF
 
   

The following is an example of a group address:

E180.0999.9999.FFFF
 
   

An SMDS network can be thought of in much the same way as an X.25 cloud. The premises equipment (in this case Cisco routers) 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 from one protocol family to another.

One major difference between protocol families is dynamic versus static routing among the routers (called remote peers) on the periphery of the cloud. For IP, routing across the SMDS cloud is fully dynamic. No action on the user's part is needed to map higher-level protocol addresses to SMDS addresses. Both IP and ARP can be configured and a dynamic ARP routing table enabled.


Note The arp smds command requires 12-digit dotted-notation SMDS addresses—for example, C141.5678.9012.


Customizing the SMDS Network

Configuring Specific Protocols

Transparent Bridging over SMDS

SMDS Subinterfaces for Multiple Logical IP Subnetworks

Reenabling Data Exchange Interface Version 3.2 with Heartbeat Support

Pseudobroadcasting

Fast Switching

Configuring 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 need to be made only 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 1 lists protocol families and the multicasts that are needed.

Table 1 Protocol Families and Types of Multicasts Needed

Protocol Family
Multicasts Needed

IP

IP

DECnet

DECNET, DECNET_NODE, DECNET_ROUTER-L1, DECNET_ROUTER-L2

CLNS

CLNS, CLNS_ES,CLNS_IS

Novell IPX

IPX

XNS

XNS

AppleTalk

APPLETALK, AARP

Banyan VINES

VINES


Configuring ARP and IP

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

Configuring 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.

Configuring CLNS

Multicasts must be configured for CLNS_ES and CLNS_IS. No static maps are necessary. End system hello (ESH), intermediate system hello (ISH), and router hello packets are sent to the multicast address, and neighbor entries are created automatically.

Configuring IPX

For Novell IPX, the multicast address must be configured. A static map entry can be made for each remote peer, or you can use the smds glean command to dynamically map addresses. Static map entries override any dynamic map entries.

Routing Information Protocol (RIP) routing packets, Service Advertisement Protocol (SAP) packets, NetBIOS Name Lookups, directed broadcasts, and traffic to the helper addresses (if that helper address is a broadcast address) are sent to the SMDS IPX multicast address.

Configuring XNS

For XNS, the multicast address must be configured, and a static map entry must be made for each remote peer. Only RIP, directed broadcasts, and helper traffic are sent to the XNS multicast address.

Configuring 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 information on the appletalk address and appletalk cable-range commands, refer to the Cisco IOS AppleTalk and Novell IPX Command Reference.

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

Configuring Banyan VINES

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

Transparent Bridging over SMDS

You can enable transparent bridging for SMDS encapsulated serial and HSSI interfaces. Cisco's implementation of IEEE 802.6i transparent bridging for SMDS supports 802.3, 802.5, and FDDI frame formats. The router can accept frames with or without frame check sequence (FCS).

Fast-switched transparent bridging is the default and is not configurable. If a packet cannot be fast switched, it will be process switched.

For more information about bridge groups and the bridge-group command, see the "Configuring Transparent Bridging" chapter in the Cisco IOS Bridging and IBM Networking Configuration Guide.

SMDS Subinterfaces for Multiple Logical IP Subnetworks

Multiple logical IP subnetworks are supported as defined by RFC 1209. This RFC explains 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.

This solution allows a single SMDS interface to be treated as multiple logical IP subnetworks and to support routing of packets from one network to the next without using intervening routers. When multiple logical IP subnetworks are enabled, the router performs routing between the subnetworks using IP addresses on an SMDS interface. Each supported subnetwork 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.

Only routers that require knowledge of multiple IP networks need to be configured with multipoint subinterfaces that correspond to different networks.

Reenabling 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. The DXI mechanism encapsulates SMDS packets in a DXI frame before they are transmitted. The heartbeat mechanism automatically generates a heartbeat poll frame every 10 seconds. The Interim Local Management Interface (ILMI) is not supported. See the Cisco IOS Wide-Area Networking Command Reference for more information about DXI 3.2.


Note If you are running serial lines back-to-back, disable keepalive on SMDS interfaces. Otherwise, DXI declares the link down.


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

Fast Switching

SMDS fast switching of IP, IPX, and AppleTalk 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.

SMDS Configuration Task List

Enabling SMDS on the Interface

Customizing Your SMDS Network

Monitoring the SMDS Connection

Enabling SMDS on the Interface

Setting SMDS Encapsulation

Specifying the SMDS Address

Establishing Address Mapping

Mapping a Multicast Address to an SMDS Address

Enabling ARP

Enabling Broadcast ARP Messages

Enabling Dynamic Address Mapping for IPX over SMDS

Setting SMDS Encapsulation

To set SMDS encapsulation at the interface level, use the following command in interface configuration mode:

Command
Purpose

Router(config-if)# encapsulation smds

Enables SMDS on the interface.


Specifying the SMDS Address

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

Command
Purpose

Router(config-if)# smds address smds-address

Enters an individual address provided by the SMDS service provider.


Establishing Address Mapping

Routing tables are configured dynamically when DECnet, extended AppleTalk, IP, IPX, and ISO CLNS routing are configured. However, you can configure static mapping for these protocols, if needed. For other protocols, you must configure a static map between an individual SMDS address and a higher-level protocol address.

To establish address mapping, use the following command in interface configuration mode:

Command
Purpose

Router(config-if)# smds static-map protocol protocol-address smds-address [broadcast]

Defines static entries for those routers that are SMDS remote peers.

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


Mapping 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 do so, you need not specify the broadcast keyword in the smds static-map command, and the Cisco IOS software need not replicate each broadcast address.

To map an SMDS group address to a multicast address, use the following command in interface configuration mode:

Command
Purpose

Router(config-if)# smds multicast protocol smds-address

Maps an SMDS group address to a multicast address used by a higher-level protocol. The protocols supported and the keywords to enable them are as follows:

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

Note Bridging is not a protocol, but the bridge keyword is valid for providing a map to a multicast address.


Enabling 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, use one of the following commands in the specified configuration mode:

Command
Purpose

Router(config-if)# smds enable-arp

Enables ARP and dynamic address resolution (interface).

Router(config)# arp ip-address smds-address smds

Enables ARP with a static entry for the remote router (global).


Enabling 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, use the following commands in interface configuration mode:

 
Command
Purpose

Step 1 

Router(config-if)# smds enable-arp

Enables ARP and dynamic address resolution.

Step 2 

Router(config-if)# smds multicast arp smds-address [ip-address mask]

Enables broadcast ARP messages.

Enabling Dynamic Address Mapping for IPX over SMDS

To enable dynamic address mapping for IPX on an SMDS interface, use the following command in interface configuration mode:

Command
Purpose

Router(config-if)# smds glean ipx [timeout-value] [broadcast]

Enables dynamic address mapping for IPX.


Customizing Your SMDS Network

Configuring Specific Protocols

Enabling Transparent Bridging over SMDS

Configuring SMDS Subinterfaces for Multiple Logical IP Subnetworks

Reenabling Data Exchange Interface Version 3.2 with Heartbeat Support

Configuring Pseudobroadcasting

Enabling Fast Switching

Enabling Transparent Bridging over SMDS

To enable transparent bridging, use the following commands beginning in global configuration mode:

 
Command
Purpose

Step 1 

Router(config)# interface type number

Specifies a serial or HSSI interface.

Step 2 

Router(config-if)# encapsulation smds

Configures SMDS encapsulation on the serial interface.

Step 3 

Router(config-if)# bridge-group bridge-group

Associates the interface with a bridge group.

Step 4 

Router(config-if)# smds multicast bridge smds-address

Configures bridging across SMDS.

Configuring SMDS Subinterfaces for Multiple Logical IP Subnetworks

To configure the Cisco IOS software to have multipoint subinterfaces for multiple logical IP subnetworks, use the following commands beginning in global configuration mode:

 
Command
Purpose

Step 1 

Router(config)# interface serial interface.subinterface multipoint

Router(config)# interface serial slot/port.subinterface multipoint

(for Cisco 7000 series routers1 )

Defines a logical subinterface for each IP network.

Step 2 

Router(config-if)# ip address ip-address mask

Configures the subinterface as an IP network.

Step 3 

Router(config-if)# smds address smds-address

Assigns unicast SMDS E.164 address to the subinterface.

Step 4 

Router(config-if)# smds multicast protocol smds-address

Assigns multicast SMDS E.164 address for each protocol supported on the subinterface.

Step 5 

Router(config-if)# smds enable-arp

Enables ARP on the subinterface, if required by the protocol.

1 Beginning in Cisco IOS Release 11.3, all commands supported on the Cisco 7500 series are also supported on the Cisco 7000 series.

Reenabling Data Exchange Interface Version 3.2 with Heartbeat Support

To reenable the DXI heartbeat, use the following command in interface configuration mode:

Command
Purpose

Router(config-if)# smds dxi

Enables DXI 3.2.


Configuring Pseudobroadcasting

To configure pseudobroadcasting, use the following command in interface configuration mode:

Command
Purpose

Router(config-if)# smds static-map protocol protocol-address smds-address broadcast

Configures pseudobroadcasting.


For an example of how to configure pseudobroadcasting, see the section "Pseudobroadcasting Example" later in this chapter.

Enabling Fast Switching

To re-enable fast switching, use the following commands beginning in global configuration mode:

 
Command
Purpose

Step 1 

Router(config)# interface type number

Defines and enters interface configuration mode.

Step 2 

Router(config-if)# encapsulation smds

Sets SMDS encapsulation.

Step 3 

Router(config-if)# ip route-cache

Enables the interface for IP fast switching.

Step 4 

Router(config-if)# ipx route-cache

Enables the interface for IPX fast switching.

Step 5 

Router(config-if)# appletalk route-cache

Enables the interface for AppleTalk fast switching.

Monitoring the SMDS Connection

To monitor the SMDS connection, use one or more of the following commands in EXEC mode:

Command
Purpose

Router# show arp

Monitors ARP activity.

Router# show smds addresses

Displays the individual addresses and the interface with which they are associated.

Router# show smds map

Displays all SMDS addresses that are mapped to higher-level protocol addresses.

Router# show smds traffic

Displays packet traffic activity.


SMDS Configuration Examples

Typical Multiprotocol Configuration Example

Remote Peer on the Same Network Example

IPX Dynamic Address Mapping Example

AppleTalk Configuration Examples

Multiple Logical IP Subnetworks 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.

interface serial 4
 ip address 1.1.1.2 255.0.0.0
 decnet cost 4
 appletalk address 92.1
 appletalk zone smds
 clns router igrp FOO
 ipx net 1a
 xns net 17
 encapsulation SMDS
! SMDS configuration follows
 smds address c120.1580.4721
 smds static-map APPLETALK 92.2 c120.1580.4592
 smds static-map APPLETALK 92.3 c120.1580.4593
 smds static-map APPLETALK 92.4 c120.1580.4594
 smds static-map NOVELL 1a.0c00.0102.23ca c120.1580.4792
 smds static-map XNS 17.0c00.0102.23ca c120.1580.4792
 smds static-map NOVELL 1a.0c00.0102.23dd c120.1580.4728
 smds static-map XNS 17.0c00.0102.23aa c120.1580.4727
 smds multicast NOVELL e180.0999.9999
 smds multicast XNS e180.0999.9999
 smds multicast ARP e180.0999.9999
 smds multicast IP e180.0999.9999
 smds multicast APPLETALK e180.0999.9999
 smds multicast AARP e180.0999.9999
 smds multicast CLNS_IS e180.0999.9990
 smds multicast CLNS_ES e180.0999.9990
 smds multicast DECNET_ROUTER e180.0999.9992
 smds multicast DECNET_NODE e180.0999.9992
 smds multicast DECNET e180.0999.9992
 smds enable-arp

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.

interface serial 0
 ip address 1.1.1.1 255.0.0.0
 decnet cost 4
 appletalk address 92.2
 appletalk zone smds
 clns router igrp FOO
 ipx net 1a
 xns net 17
 encapsulation SMDS
! SMDS configuration follows
 smds address c120.1580.4792
 smds static-map APPLETALK 92.1 c120.1580.4721
 smds static-map APPLETALK 92.3 c120.1580.4593
 smds static-map APPLETALK 92.4 c120.1580.4594
 smds static-map NOVELL 1a.0c00.0102.23cb c120.1580.4721
 smds static-map XNS 17.0c00.0102.23cb c120.1580.4721
 smds static-map NOVELL 1a.0c00.0102.23dd c120.1580.4728
 smds static-map XNS 17.0c00.0102.23aa c120.1580.4727
 smds multicast NOVELL e180.0999.9999
 smds multicast XNS e180.0999.9999
 smds multicast IP e180.0999.9999
 smds multicast APPLETALK e180.0999.9999
 smds multicast AARP e180.0999.9999
 smds multicast CLNS_IS e180.0999.9990
 smds multicast CLNS_ES e180.0999.9990
 smds multicast DECNET_ROUTER e180.0999.9992
 smds multicast DECNET_NODE e180.0999.9992
 smds multicast DECNET e180.0999.9992
 smds enable-arp

IPX Dynamic Address Mapping Example

The following example enables dynamic address mapping for IPX on interface serial 0 and sets the time to live (TTL) to 14 minutes.

interface serial 0
 encapsulation smds
 smds address c141.5797.1313
 smds multicast ipx e180.0999.9999
 smds glean ipx 14

AppleTalk Configuration Examples

The following two sections provide basic examples of configuration for an extended AppleTalk network and for a nonextended AppleTalk network. For more information on AppleTalk commands, refer to the Cisco IOS AppleTalk and Novell IPX Command Reference.

Extended AppleTalk Network Example

If all AppleTalk routers on the SMDS cloud are running Cisco IOS Release 10.3(4) or later releases, you can use an AppleTalk extended network. To do so, use 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.

interface Serial0
 ip address 192.168.200.1 255.255.255.0
 encapsulation smds
 appletalk cable-range 10-10
 appletalk zone SMDS
 smds address c151.0988.1923
 smds static-map ip 192.168.200.2 c151.0988.8770
 smds multicast APPLETALK e151.0988.2232
 smds multicast AARP e151.0988.2232
 smds multicast IP e151.0988.2232
 smds multicast ARP e151.0988.2232
 smds enable-arp

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 and the appletalk address command is used. Dynamic AppleTalk Address Resolution Protocol (AARP) is not supported on the multicast channel.

interface Serial0
 ip address 192.168.200.1 255.255.255.0
 encapsulation smds
 appletalk address 10.1
 appletalk zone SMDS
 smds address c151.0988.1923
 smds static-map ip 192.168.200.2 c151.0988.8770
 smds static-map appletalk 10.2 c151.0988.8770
 smds multicast APPLETALK e151.0988.2232
 smds multicast IP e151.0988.2232
 smds multicast ARP e151.0988.2232
 smds enable-arp

Multiple Logical IP Subnetworks over SMDS Example

In the following example, routers A, B, and C are connected to an SMDS cloud by means of two logical subnetworks labeled 1 and 2, as shown in Figure 2.

Router A recognizes two IP networks and can communicate with Routers B and C directly. Router B can communicate with router A directly, and with router C through router A. Router C can communicate with router A directly and with router B through 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. Notice also that this configuration is nonstandard. This issue was considered when the multiple logical IP subnetworks proposal was made, and was deemed not to be critical.

Figure 2 Multiple Logical IP Subnetworks Configuration

The following example shows all routers as Cisco 7200 routers, but they can be other platforms.

Configuration for Router A

interface serial 2/0 
 encapsulation smds
!
interface serial 2/0.1 multipoint
 smds addr c111.3333.3333
 ip address 2.2.2.1 255.0.0.0
 smds multicast ip e122.2222.2222
 smds enable-arp 
 smds multicast ARP e122.2222.2222

Configuration for Router B

interface serial 4/0
 encapsulation smds
 smds address c111.2222.2222
 ip address 1.1.1.3 255.0.0.0
 smds multicast ip e180.0999.9999
 smds enable-arp

Configuration for Router C

interface serial 1/0
 encapsulation smds
 smds address c111.4444.4444
 ip address 2.2.2.2 255.0.0.0
 smds multicast ip e122.2222.2222
 smds enable-arp

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

interface s 0
 encapsulation smds
 smds address c120.1111.2222
 ip address 172.20.1.30 255.255.255.0
 smds multicast ip e180.0999.9999
 smds static-map ip 172.20.1.10 c120.1234.5678 broadcast
 smds enable-arp

Configuration for Router B

interface s 4
 smds address c120.9999.8888
 ip address 172.20.1.20
 smds multicast ip e180.0999.9999
 smds enable-arp

Configuration for Router C

interface serial 2
 smds address c120.1234.5678
 ip address 172.20.1.10
 smds static-map ip 172.20.1.30 c120.1111.2222 broadcast
 smds enable-arp 
 
   

Feature Information for SMDS

Table 2 lists the features in this module and provides links to specific configuration information.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.


Note Table 2 lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.


Table 2 Feature Information for <Phrase Based on Module Title> 

Feature Name
Releases
Feature Information

Switched Multimegabit Data Service (SMDS)

11.2(1)
15.0(1)S

The Switched Multimegabit Data Service (SMDS) is a WAN service offered by a variety of service providers.

The following sections provide information about this feature:

Information About SMDS

SMDS Configuration Task List