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Configuring SMDS

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 Wide-Area Networking Command Reference.

SMDS Hardware Requirements

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

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.

Figure 41 illustrates the connections between the different components.


Figure 41: 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 Previous 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. Previous 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

For additional technical references about SMDS, see the "References and Recommended Readings" appendix in the Configuration Fundamentals Command Reference.

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:

You must perform basic steps 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:

See the "SMDS Configuration Examples" section 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

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

Task Command
Enable SMDS on the interface. encapsulation smds

For examples of enabling SMDS encapsulation, see 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:

Task Command
Enter an individual address provided by the SMDS service provider. smds address smds-address

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

Establish 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, perform the following task in interface configuration mode:

Task Command
Define static entries for those routers that are SMDS remote peers. smds static-map protocol protocol-address smds-address [broadcast]

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

For examples of establishing address mapping, see 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 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, perform the following task in interface configuration mode:

Task Command
Map an SMDS group address to a multicast address used by a higher-level protocol. smds multicast protocol smds-address

The protocols supported and the keywords to enable them are as follows. Note that bridging is not a protocol, but the bridge keyword is valid for providing a map to a multicast address.

For examples of mapping to a multicast address, see the examples in the section "SMDS Configuration Examples" later in this chapter.

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:

Task Command
Enable ARP and dynamic address resolution. smds enable-arp
Enable ARP with a static entry for the remote router. arp ip-address smds-address smds

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 between protocol families.

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.

See the section "Configure Specific Protocols" later in this chapter for more information about configuring higher-level protocols.

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 tasks in interface configuration mode:

Task Command
Enable ARP and dynamic address resolution. smds enable-arp
Enable broadcast ARP messages. smds multicast arp smds-address [ip-address mask]

For an example of how to enable broadcast ARP messages, see the section "Typical Multiprotocol Configuration Example" later in this chapter.

Enable Dynamic Address Mapping for IPX over SMDS

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

Task Command
Enable dynamic address mapping for IPX. smds glean ipx [timeout-value] [broadcast]

For an example of how to enable dynamic address mapping for IPX over SMDS, see the section "IPX Dynamic Address Mapping Example" later in this chapter.

Customize Your SMDS Network

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

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 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 6 lists protocol families and the multicasts that are needed.


Table 6: 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

Configure 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.

Configure 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.

Configure 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.

Configure 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.

Configure 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.

Configure 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 Network Protocols Command Reference, Part 2.

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

Configure Banyan VINES

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

Enable 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.

To enable transparent bridging, perform the following tasks in interface configuration mode:

Task Command
Step 1 Specify a serial or HSSI interface. interface type number1
Step 2 Configure SMDS encapsulation on the serial interface. encapsulation smds
Step 3 Associate the interface with a bridge group. bridge-group bridge-group2
Step 4 Configure bridging across SMDS. smds multicast bridge smds-address

1 This command is documented in the "Interface Commands" chapter in the Configuration Fundamentals Command Reference.
2 This command is documented in the "Transparent Bridging Commands" chapter in the Bridging and IBM Networking Command Reference.

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

Configure 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.

To configure the Cisco IOS software to have multipoint subinterfaces for multiple logical IP subnetworks, perform the following tasks in interface configuration mode:

Task Command
Step 1 Define a logical subinterface for each IP network. interface serial number.subinterface-number multipoint1

interface serial slot/port.subinterface multipoint1
(for Cisco 7000 series routers)

Step 2 Configure the subinterface as an IP network. ip address ip-address mask2
Step 3 Assign a unicast SMDS E.164 address to the subinterface. smds address smds-address
Step 4 Assign a multicast SMDS E.164 address for each protocol supported on the subinterface. smds multicast protocol smds-address
Step 5 Enable ARP on the subinterface, if required by the protocol. smds enable-arp

1 This command is documented in the "Interface Commands" chapter of the Configuration Fundamentals Command Reference.
2 This command is documented in the "IP Commands" chapter of the Network Protocols Command Reference, Part 1.

For an example of how to configure multiple logical IP subnetworks, see the "Multiple Logical IP Subnetworks 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. 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 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.

If you find you must reenable the DXI heartbeat, perform the following task in interface configuration mode:

Task Command
Configure DXI 3.2. smds dxi

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 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.

To configure pseudobroadcasting, perform the following task in interface configuration mode:

Task Command
Configure pseudobroadcasting. smds static-map ip ip-address smds-address broadcast

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

Enable 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.

To re-enable fast switching, perform the following tasks in interface configuration mode:

Task Command
Step 1 Define the type and unit number of the interface, and enter interface configuration mode. interface type number1
Step 2 Set SMDS encapsulation. encapsulation smds
Step 3 Enable the interface for IP fast switching. ip route-cache2
Step 4 Enable the interface for IPX fast switching. ipx route-cache3
Step 5 Enable the interface for AppleTalk fast switching. appletalk route-cache4

1 This command is documented in the "Interface Commands" chapter in the Configuration Fundamentals Command Reference.
2 This command is documented in the "IP Commands" chapter in the Network Protocols Command Reference, Part 1.
3 This command is documented in the "Novell IPX Commands" chapter in the Network Protocols Command Reference, Part 2.
4 This command is documented in the "AppleTalk Commands" chapter in the Network Protocols Command Reference, Part 2.

Monitor the SMDS Connection

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

Task Command
Monitor ARP activity. show arp
Display the individual addresses and the interface with which they are associated. show smds addresses
Display all SMDS addresses that are mapped to higher-level protocol addresses. show smds map
Display packet traffic activity. show smds traffic

SMDS Configuration Examples

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

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 Network Protocols Command Reference, Part 2.

Extended AppleTalk Network Example

If all AppleTalk routers on the SMDS cloud are running Cisco IOS software Release 10.3(4) (or later), 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 labelled 1 and 2 (see Figure 42).

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 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. 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 42: Multiple Logical IP Subnetworks Configuration


The following example shows all routers as Cisco 7000 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 


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