Configuring SMDS

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.

The table below lists protocol families and the multicasts that are needed.

• Configuring ARP and IP
  
• Configuring DECnet
  
• Configuring CLNS
  
• Configuring IPX
  
• Configuring XNS
  
• Configuring AppleTalk
  
• Configuring Banyan VINES
  

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 .

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.

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.

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.

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

Router(config-if)# encapsulation smds

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

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

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:

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

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:

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

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:

Router(config-if)# smds enable-arp

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

1.    Router(config-if)# smds enable-arp

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

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

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

1.    Router(config)# interface type number

2.    Router(config-if)# encapsulation smds

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

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

1.    Router(config)# interface serial interface . subinterface multipoint

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

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

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

5.    Router(config-if)# smds enable-arp

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

Router(config-if)# smds dxi

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

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

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

1.    Router(config)# interface type number

2.    Router(config-if)# encapsulation smds

3.    Router(config-if)# ip route-cache

4.    Router(config-if)# ipx route-cache

5.    Router(config-if)# appletalk route-cache

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

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