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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 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 an RS-449 connection. 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.
IP routing 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.
And finally, when a multicast address is not available to a destination, pseudobroadcasting can be enabled to broadcast packets to those destinations using a unicast address.
All addresses for SMDS service are assigned by the service provider and can be assigned to individuals and groups.
Addresses are entered in the Cisco SMDS configuration software using an E prefix for Multicast addresses and a C prefix for Unicast addresses.
Our 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 when broadcasting 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.
An example of an E.164 address follows:
C14155561313FFFF
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 Router Products Command Reference publication.
You need the following hardware, equipment, and special software to configure SMDS:
Figure 1-1 illustrates the connections between the different components.
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:
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:
See the examples at the end of this chapter for ideas of how to configure SMDS on your network.
You must perform the tasks in the following sections to enable SMDS:
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 any of the examples in the section "SMDS Configuration Examples" later in this chapter.
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 any of the examples in the section "SMDS Configuration Examples" later in this chapter.
Routing tables are configured dynamically when IP and CLNS routing are configured. 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:
| Task | Command |
|---|---|
| Define static entries for those routers that are SMDS remote peers. | smds static-map protocol-type protocol-address smds-address [broadcast] |
The supported protocols and the keywords to enable them are as follows.
For examples of establishing address mapping, see any of the examples in the section "SMDS Configuration Examples" later in this chapter.
You can map an SMDS group address to a broadcast or multicast address used by higher-level protocols. If you use this feature, 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. To map 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 higher-level protocols. | smds multicast protocol-type 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, see any of the examples in the section "SMDS Configuration Examples" later in this chapter.
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.
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.
See the section "Configure Specific Protocols" later in this chapter for more information about configuring higher-level protocols.
When multicast service is available and an ARP server is present in the network, you can enable broadcast ARP messages to be 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:
| Task | Command |
|---|---|
| Enable ARP and dynamic address resolution. | smds enable-arp |
| Enable broadcast ARP messages. | smds multicast ip smds-address or smds multicast arp smds-address |
If the smds multicast ip command is used, the smds multicast arp command is optional. ARP requests will go to the IP multicast address if no ARP multicast address is specified. If an SMDS multicast ARP address is specified, ARP requests go to that address.
Perform the tasks in the following sections, as appropriate, for your network:
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 1-1 lists protocol families and the multicasts that are needed.
| Protocol Family | Multicasts Needed |
|---|---|
| IP | IP |
| DECnet | DECNET, DECNET_NODE, DECNET_ROUTER |
| CLNS | CLNS, CLNS_ES,CLNS_IS |
| Novell IPX | NOVELL |
| XNS | XNS |
| AppleTalk | APPLETALK, AARP |
| Banyan VINES | VINES |
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.
Static maps must be configured for DECnet. In addition, a separate smds multicast command is needed for DECNET, DECNET_NODE, and DECNET_ROUTER.
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.
For XNS and IPX, the multicast address must be configured.
For IPX, RIP routing packets, SAP packets, NetBIOS Name Lookups, directed broadcasts, and traffic to the helper addresses (if that helper address is a broadcast address) will be sent to the SMDS IPX multicast address.
For XNS, only RIP, directed broadcasts, and helper traffic will be sent to the XNS multicast address.
For XNS and Novell configurations, a static map entry must be made for each remote peer.
Currently, dynamic address assignment is not supported. AppleTalk only works with static maps. Therefore, an AppleTalk address must be assigned to the interface. ARP must be enabled and multicasts must be used for the AppleTalk protocol to work.
For Banyan VINES, the multicast address must be configured. Also note that VINES only works with static maps.
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:
| Task | Command |
|---|---|
| Configure bridging across SMDS. | smds multicast bridge smds-address |
See the "Configuring Transparent Bridging" chapter for more information about bridge groups and the bridge-group command.
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 points to cases where traffic must transit from network to network.
The MultiLIS solution allows a single SMDS interface to be treated as multiple IP subnets and to support routing of packets from one network to the next without using intervening routers. When enabled, the router will perform routing between the subnets configured using secondary IP addresses on an SMDS interface. Each supported subnet has a secondary IP address and multicast IP 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 multiple logical IP subnets, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
| Configure MultiLIS. | smds multicast ip smds-address [ip-address-mask] |
For an example of how to configure MultiLIS, see the section "Example of Configuring a MultiLIS Network" later in this chapter.
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:
| Task | Command |
|---|---|
| Configure DXI 3.2. | smds dxi |
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 Router Products Command Reference publication for more information about DXI 3.2.
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.
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 section "Example of Configuring Pseudobroadcasting" later in this chapter.
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.
| Task | Command |
|---|---|
| Step 1 Define the type and unit number of the interface, and enter interface configuration mode. | interface type unit1 |
| Step 2 Set SMDS encapsulation. | encapsulation smds |
| Step 3 Enable the interface for fast switching. | ip route-cache2 |
To monitor the SMDS connection, perform one or more of the following tasks in EXEC mode:
The following section provides typical configuration file examples you can use as models for your network configurations:
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.FFFF
smds static-map APPLETALK 92.3 c120.1580.4593.FFFF
smds static-map APPLETALK 92.4 c120.1580.4594.FFFF
smds static-map NOVELL 1a.0c00.0102.23ca c120.1580.4792.FFFF
smds static-map XNS 17.0c00.0102.23ca c120.1580.4792.FFFF
smds static-map NOVELL 1a.0c00.0102.23dd c120.1580.4728.FFFF
smds static-map XNS 17.0c00.0102.23aa c120.1580.4727.FFFF
smds multicast NOVELL e180.0999.9999.FFFF
smds multicast XNS e180.0999.9999.FFFF
smds multicast ARP e180.0999.9999.FFFF
smds multicast IP e180.0999.9999.FFFF
smds multicast APPLETALK e180.0999.9999.FFFF
smds multicast AARP e180.0999.9999.FFFF
smds multicast CLNS_IS e180.0999.9990.FFFF
smds multicast CLNS_ES e180.0999.9990.FFFF
smds multicast DECNET_ROUTER e180.0999.9992.FFFF
smds multicast DECNET_NODE e180.0999.9992.FFFF
smds multicast DECNET e180.0999.9992.FFFF
smds enable-arp
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.FFFF
smds static-map APPLETALK 92.3 c120.1580.4593.FFFF
smds static-map APPLETALK 92.4 c120.1580.4594.FFFF
smds static-map NOVELL 1a.0c00.0102.23cb c120.1580.4721.FFFF
smds static-map XNS 17.0c00.0102.23cb c120.1580.4721.FFFF
smds static-map NOVELL 1a.0c00.0102.23dd c120.1580.4728.FFFF
smds static-map XNS 17.0c00.0102.23aa c120.1580.4727.FFFF
smds multicast NOVELL e180.0999.9999.FFFF
smds multicast XNS e180.0999.9999.FFFF
smds multicast IP e180.0999.9999.FFFF
smds multicast APPLETALK e180.0999.9999.FFFF
smds multicast AARP e180.0999.9999.FFFF
smds multicast CLNS_IS e180.0999.9990.FFFF
smds multicast CLNS_ES e180.0999.9990.FFFF
smds multicast DECNET_ROUTER e180.0999.9992.FFFF
smds multicast DECNET_NODE e180.0999.9992.FFFF
smds multicast DECNET e180.0999.9992.FFFF
smds enable-arp
In the following example, Routers A, B, and C are connected to an SMDS cloud (see Figure 1-2).
Router A 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 talk to Router A directly and to 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.
interface serial 0
smds address c120.FFFF.2222
ip address 131.108.1.30 255.255.255.0
ip address 131.108.5.30 255.255.255.0 secondary
smds multicast ip e180.0999.9999.FFFF
smds multicast ip e180.0333.3333.FFFF 131.108.5.0 255.255.255.0
interface serial 4
smds address c120.9999.8888
ip address 131.108.5.20 255.255.255.0
ip address 131.108.1.20 255.255.255.0 secondary
smds multicast ip e180.0333.3333.FFFF
smds multicast ip e180.0999.9999.FFFF 131.108.1.0 255.255.255.0
interface serial 2
smds address c120.1234.5678.FFFF
ip address 131.108.1.10 255.255.255.0
smds multicast ip e180.0999.9999.FFFF 255.255.255.0
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.
interface s 0
encapsulation smds
smds address c120.1111.2222.FFFF
ip address 131.108.1.30 255.255.255.0
smds multicast ip e180.0999.9999.FFFF
smds static-map ip 131.108.1.10 c120.1234.5678.FFFF broadcast
smds enable-arp
interface s 4
smds address c120.9999.8888.FFFF
ip address 131.108.1.20
smds multicast ip e180.0999.9999.FFFF
smds enable-arp
interface serial 2
smds address c120.1234.5678.FFFF
ip address 131.108.1.10
smds static-map ip 131.108.1.30 c120.1111.2222.FFFF broadcast
smds enable-arp
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