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Use the commands in this chapter to configure the Switched Multimegabit Data Service (SMDS), a wide-area networking service offered by some Regional Bell Operating Companies (RBOCs) and MCI.
For SMDS configuration information and examples, refer to the "Configuring SMDS" chapter in the Router Products Configuration Guide.
Use the following variation of the arp global configuration command to enable ARP entries for static routing over the SMDS network. Use the no form of this command to disable this capability.
This command requires a 12-digit (48-bit) dotted-format SMDS address. It does not support 15-digit SMDS addresses.
The following example creates a static ARP entry that maps the IP address 131.108.173.28 to the SMDS address C141.5797.1313 on interface serial 0:
smds enable-arp
smds static-map
Use the encapsulation smds interface configuration command to enable SMDS service on the desired interface.
This command has no arguments or keywords.
The interface to which this command applies must be a serial interface. All subsequent SMDS configuration commands only apply to an interface with encapsulation SMDS.
Note The maximum packet size allowed in the SMDS specifications
(TA-772) is 9188. This is larger than the packet size used by servers with most media. The Cisco
default MTU size is 1500 bytes to be consistent with Ethernet. However, on HSSI interfaces, the
default MTU size is 4470 bytes. If a larger MTU is used, the mtu command must be entered before
the encapsulation smds command.
Keep in mind, however, that the Cisco MCI card has buffer limitations that prevent setting the MTU
size higher than 2048, and the HSSI card has buffer limitations that prevent setting the MTU size
higher than 4500. Configuring higher settings has caused router inconsistencies and performance
problems.
The following example shows how to configure the SMDS service on serial interface 0:
A dagger () indicates that the command is documented in another chapter.
Use the show arp privileged EXEC command to display the entries in the ARP table for the router.
This command has no arguments or keywords.
The following is sample output from the show arp command:
Table 11-1 describes significant fields shown in the first line of output in the display.
Table 11-1 Show ARP Field Descriptions
Use the show smds addresses privileged EXEC command to display the individual addresses and the interface they are associated with.
This command has no arguments or keywords.
The following is sample output from the show smds addresses command:
Table 11-2 describes the fields shown in the display.
Table 11-2 Show SMDS Addresses Field Descriptions
| Field | Description |
|---|---|
To display all SMDS addresses that are mapped to higher-level protocol addresses, use the show smds map privileged EXEC command.
This command has no arguments or keywords.
The following is sample output from the show smds map command:
Table 11-3 describes the fields shown in the output.
Table 11-3 Show SMDS Map Field Descriptions
To display statistics about bad SMDS packets the router has received, use the show smds traffic privileged EXEC command.
This command has no arguments or keywords.
The following is sample output from the show smds traffic command:
Table 11-4 describes the fields shown in the output.
Table 11-4 Show SMDS Traffic Field Descriptions
To specify the SMDS individual address for a particular interface, use the smds address interface configuration command. To remove the address from the configuration file, use the no form of this command.
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. 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.
The following example specifies an individual address in Ethernet-style notation:
To enable the DXI 3.2 support, use the smds dxi interface configuration command. To disable the DXI 3.2 support, use the no form of this command.
This command has no arguments or keywords.
Adding this command to the configuration enables the Data Exchange Interface (DXI) version 3.2 mechanism and encapsulates SMDS packets in a DXI frame before they are transmitted. DXI 3.2 adds an additional four bytes to the SMDS packet header to communicate with the SDSU. These bytes specify the frame type. The interface will expect all packets to arrive with DXI encapsulation.
The DXI 3.2 support also includes the heartbeat process as specified in the SIG-TS-001/1991 standard, revision 3.2. The heartbeat (active process) is enabled when both DXI and keepalives are enabled on the interface. The echo (passive process) is enabled when DXI is enabled on the interface. The heartbeat mechanism automatically generates a heartbeat poll frame every 10 seconds. This default value can be changed with the keepalive command. The Interim Local Management Interface (ILMI) is not supported.
Note If you are running serial lines back to back, disable keepalive on SMDS interfaces. Otherwise, DXI will declare the link down.
Note Switching in or out of DXI mode causes the IP cache to be cleared. This is necessary to remove all cached IP entries for the serial line being used. Stale entries must be removed to allow the new MAC header with or without DXI framing to be installed in the cache. This is not frequently done and is not considered to be a major performance penalty.
Fast switching of DXI frames is also supported as of this software release.
The following example enables DXI 3.2 on interface HSSI 0:
A dagger () indicates that the command is documented in another chapter.
To enable dynamic Address Resolution Protocol (ARP), use the smds enable-arp interface configuration command. The multicast address for ARP must be set before this command is issued. Once ARP has been enabled, use the no form of this command to disable the interface.
This command has no arguments or keywords.
The following example enables the dynamic ARP routing table:
To assign a multicast SMDS E.164 address to a higher-level protocol, use the smds multicast interface configuration command. To remove an assigned multicast address, use the no form of this command with the appropriate address.
Protocol type. See the "SMDS Multicast Supported Protocols" table in the "Usage Guidelines" section for a list of supported protocols and their keywords. |
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SMDS address. Because SMDS does not incorporate broadcast addressing, a group address for a particular protocol must be defined to serve the broadcast function. |
When configuring DECnet, all four DEC keywords (decnet, decnet_router-L1, decnet_router-L2, and decnet_node) must be entered in the configuration.
Table 11-5 lists the high-level protocols supported by the smds multicast command.
Table 11-5 SMDS Multicast Supported Protocols
| Keyword | Protocol |
|---|---|
DECnet multicast address for all Level 1 (intra-area) routers |
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DECnet multicast address for all Level 2 (interarea) routers |
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For IP, the IP NETwork and MASK fields are no longer required. The router will accepts these arguments, but will ignore the values. These were required commands for the previous Multi-LIS configuration. The router continues to accept the arguments to allow for backward compatibility, but ignores the contents.
The following example maps the IP broadcast address to the SMDS group address E180.0999.9999:
To map the SMDS address to a multicast address, use the smds multicast arp interface configuration command. Use the no form of this command to disable this feature.
This command is only used when an ARP server is present on a network. When broadcast ARPs are sent, SMDS first attempts to send the packet to all multicast ARP SMDS addresses. If none exist in the configuration, they are sent to all multicast IP SMDS multicast addresses. If the optional ARP multicast address is missing, each entered IP multicast command will be used for broadcasting.
The following example configures broadcast ARP messages:
To enable spanning tree updates, use the smds multicast bridge interface configuration command. Use the no form of this command to disable this function.
No multicast SMDS address is defined. Spanning tree updates are disabled for transparent bridging across SMDS networks.
Transparent bridging of packets across an SMDS network must already be enabled to allow this update function. Enable transparent bridging across an SMDS network by adding an SMDS interface to an active bridge group.
When the smds multicast bridge command is added to the configuration, broadcast packets will be encapsulated using the specified SMDS multicast address configured for bridging. All bridge packets are first encapsulated in an 802.3 MAC header before encapsulating in an SMDS L3 header with LLC/SNAP. The EtherType field of the 802.3 header will specify the particular packet enclosed in the bridge datagram.
Broadcast ARP packets are treated differently. Two packets are sent to the multicast address. One is sent using a standard (SMDS) ARP encapsulation, the other is sent with the ARP packet encapsulated in an 802.3 MAC header. The native ARP is sent as a regular ARP broadcast. Standard bridging commands are necessary to enable bridging on an SMDS interface.
Bridging over multiple logical IP subnets (multiLIS) is not supported in IOS Release 10.2. Bridging of IP packets in a multiLIS environment is unpredictable.
This implementation of 802.6 bridging supports the transmission and reception of only 802.3 encapsulated bridge packets. Other encapsulations will be supported in a future release.
In the following example, all broadcast bridge packets will be sent to the configured SMDS multicast address:
To map an SMDS group address to a secondary IP address, use the smds multicast ip interface configuration command. Use the no form of this command to remove the address map.
The IP address and mask will default to the primary address of the interface if they are left out of the configuration.
This command allows a single SMDS interface to be treated as multiple logical IP subnets (MultiLIS). If taking advantage of the MultiLIS support in SMDS, you can use more than one multicast address on the SMDS interface, that is, multiple commands can be entered. However, each smds multicast ip command entry must be associated with a different IP address on the SMDS interface.
Broadcasts can be sent on the SMDS interface using the multicast address. By sending broadcasts in this manner, the router is not required to replicate broadcasts messages to every remote host.
In addition, the higher-level protocols such as OSPF and IS-IS can use the multicast capability by sending one update packet or routing packet to the multicast address.
If the optional IP address and mask arguments are not present, the SMDS address and multicast address are associated with the primary IP address of the interface. This allows the command to be backward compatible with earlier versions of the software.
If an ARP multicast address is missing, each entered IP multicast command will be used for broadcasting. The ARP multicast command has the same format as the IP multicast command and is typically used only when an ARP server is present in the network.
Note All routers at the other end of the SMDS cloud must have the MultiLIS capability enabled. If you allocate a different SMDS subinterface for each logical IP subnetwork on the SMDS interface, you do not have to configure secondary IP addresses.
The following example configures an interface with two subinterfaces to support two different IP subnets with different multicast addresses to each network.
To configure a static map between an individual SMDS address and a higher-level protocol address, use the smds static-map interface configuration command. Use the no form of this command with the appropriate arguments to remove the map.
The smds static-map command provides pseudo-broadcasting by allowing the use of broadcasts on those hosts that cannot support SMDS multicast addresses.
The following example illustrates how to enable pseudo-broadcasting. In addition to broadcasting IP and ARP requests to E180.0999.9999, the device at address C120.4444.9999 will also receive a copy of the broadcast request. The host at address 131.108.1.15 is incapable of receiving multicast packets. The multicasting is simulated with this feature.
The following example illustrates how to enable multicasting. In addition to IP and ARP requests to E180.0999.9999, the device at address C120.4444.9999 will also receive a copy of the multicast request. The host at address 131.108.1.15 is incapable of receiving broadcast packets.
Posted: Wed Jul 2 23:39:40 PDT 2003
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