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The Cisco IOS 12.0(3)T software supports RFC 1483 and enables the transfer of network interconnect traffic over ATM AAL5 layer, using LLC encapsulation. RFC 1483 defines an encapsulation type for transferring LAN data via ATM networks.
All LAN protocols that use the LLC format and run on Ethernet, Token Ring, or ATM networks are encapsulated in LLC data packets transported via ATM networks.
Support for RFC 1483 in the Cisco IOS 12.0(3)T software enables:
SRB is accomplished by packet forwarding based on the next hop Route Descriptor.
This section describes the benefits of the RFC 1483 features introduced in Cisco IOS Release 12.0(3)T:
AAL5---ATM adaptation layer 5. One of the four AAL5 recommended by the ITU-T. AAL5 supports connection-oriented VBR services, and is used predominantly for the transfer of IP over ATM and LANE traffic.
ATM---Asynchronous Transfer Mode. International standard for cell relay in which multiple service types (such as voice, video, or data) are conveyed in fixed-length (53-byte) cells.
PDU---Protocol Data Unit. An OSI term for packet.
This feature is supported on the following platforms:
No MIBs are supported.
RFC 1483 is supported.
This section describes the following configuration task for RFC 1483 support:
Cisco IOS software offers the ability to encapsulate SRB traffic using RFC 1483 bridged LLC encapsulation. This provides SRB over ATM functionality that is interoperable with other vendors' implementations of SRB over ATM.
The following guidelines apply to RFC 1483 configuration:
To configure SRB over ATM, use the following commands in interface configuration mode:
| Step | Command | Purpose | ||
|---|---|---|---|---|
| interface atm slot/port | Specify the ATM interface. | ||
| interface atm slot/port [subinterface- number {multipoint | point-to-point}] | Specify the ATM main interface or subinterface that discovered PVCs will be assigned to. | ||
| atm pvc vcd vpi vci aal-encap [[midlow midhigh] [peak average [burst]]] [inarp [minutes]] [oam [seconds]] | Create a (PVC) on an ATM interface. | ||
| source-bridge local-ring bridge-number target-ring-number conserve-ring | Assign a ring number to the ATM PVC. | ||
| source-bridge spanning bridge-group | Enable the automatic spanning-tree function on a group of bridged interfaces. |
This section provides configuration examples for RFC 1483.
Figure 1 shows a back-to-back scenario with two ATM adapters that are connected. There is no ATM switch in this example.
Following are the configurations for routers A and B:
interface atm slot/port
atm clock interface atm slot/port.1 point-to-point atm pvc 1 10 12 aal5snap source-bridge 200 1 100 conserve-ring source-bridge spanning
interface atm slot/port.1 point-to-point atm pvc 2 10 12 aal5snap source-bridge 100 1 200 conserve-ring source-bridge spanning
Figure 2 shows an example with frames from Token Ring 1 destined to Token Ring 2 and an ATM switch connecting the routers.
interface atm slot/port interface atm slot/port.1 point-to-point atm pvc 1 10 12 aal5snap source-bridge 200 1 100 conserve-ring source-bridge spanning
interface atm slot/port.1 point-to-point atm pvc 2 0 12 aal5snap source-bridge 100 1 200 conserve-ring source-bridge spanning
The following configuration does not use the conserve-ring argument in the configuration and the PVC is allocated its own virtual ring number.
interface atm slot/port interface atm slot/port.1 point-to-point atm pvc 1 0 12 aal5snap source-bridge 5 1 100 source-bridge spanning
interface atm slot/port.1 point-to-point atm pvc 2 0 12 aal5snap source-bridge 6 1 100 source-bridge spanning
Figure 3 shows multiple ATM PVCs and multiple virtual rings on a router.
Following are the configurations for routers A, B, and C.
interface atm slot/port.1 point-to-point atm pvc 1 10 12 aal5snap source-bridge 200 1 100 conserve-ring source-bridge spanning interface atm slot/port.2 point-to-point atm 2 0 12 aal5snap source-bridge 300 2 101 conserve-ring source-bridge spanning
interface atm slot/port.1 point-to-point atm pvc 3 0 12 aal5snap source-bridge 100 1 200 conserve-ring source-bridge spanning
interface atm slot/port.1 point-to-point atm pvc 4 0 12 aal5snap source-bridge 101 2 300 conserve-ring source-bridge spanning
Figure 4 shows traffic going from Token Ring 1 to Token Ring 2 and Token Ring 3. Following are the configurations for routers A, B, and C.
interface atm slot/port.1 point-to-point atm pvc 1 0 12 aal5snap source-bridge 200 1 100 conserve-ring source-bridge spanning interface atm slot/port.2 point-to-point atm pvc 2 0 2 aal5snap source-bridge 300 2 100 conserve-ring source-bridge spanning
interface atm slot/port.1 point-to-point atm pvc 3 0 2 aal5snap source-bridge 100 1 200 conserve-ring source-bridge spanning
interface atm slot/port.1 point-to-point atm pvc 4 1 3 aal5snap source-bridge 100 2 300 conserve-ring source-bridge spanning
This section documents new or modified commands. All other commands used with this feature are documented in the Cisco IOS Release 12.0 command references.
Use the source-bridge interface configuration command to configure an interface for SRB. Use the no form of this command to disable SRB on an interface.
source-bridge source-ring-number bridge-number target-ring-number [conserve-ring]
source-ring-number | Ring number for the interface's Token Ring or FDDI ring. It must be a decimal number in the range 1 to 4095 that uniquely identifies a network segment or ring within the bridged Token Ring or FDDI network |
bridge-number | Number that uniquely identifies the bridge connecting the source and target rings. It must be a decimal number in the range 1 to 15. |
target-ring-number | Ring number of the destination ring on this router. The number must be unique within the bridged Token Ring or FDDI network. The target ring can also be a ring group. It must be a decimal number. |
conserve-ring | (Optional) Keyword to enable SRB over Frame Relay or ATM. When this option is configured, the SRB software does not add the ring number associated with the Frame Relay partner's virtual ring to outbound explorer frames. This option is permitted for Frame Relay and ATM subinterfaces only. |
SRB is disabled.
Interface configuration
The revised version of the source-bridge command to enable SRB over Frame Relay first appeared in Cisco IOS Release 11.2 F.
The source-bridge command was updated in Cisco IOS 12.0(3)T to provide support to ATM networks with the conserve-ring argument.
The parser automatically displays the word "active" in the source-bridge command in configurations that have SRB enabled. You do not need to enter the source-bridge command with the active keyword.
In the following example, Token Rings 129 and 130 are connected via a router:
interface tokenring 0 source-bridge 129 1 130 ! interface tokenring 1 source-bridge active 130 1 129
In the following example, an FDDI ring on one router is connected to a Token Ring on a second router across a DLSw+ link:
dlsw local-peer peer-id 132.11.11.2 dlsw remote-peer 0 tcp 132.11.11.3 interface fddi 0 no ip address multiring all source-bridge active 26 1 10 ! dlsw local-peer peer-id 132.11.11.3 dlsw remote-peer 0 tcp 132.11.11.2 interface tokenring 0 no ip address multiring all source-bridge active 25 1 10
In the following example, a router forwards frames from a locally attached Token Ring over the Frame Relay using SRB:
source-bridge ring-group 200 ! interface Serial0 encapsulation frame-relay ! interface Serial0.30 point-to-point frame-relay interface-dlci 30 ietf source-bridge 100 1 200 conserve-ring source-bridge spanning ! interface TokenRing0 source-bridge 600 1 200
debug frame-relay packet
debug source bridge
debug source error
debug source event
encapsulation frame-relay
frame-relay interface-dlci
source-bridge ring-group
source-bridge transparent
Posted: Thu Feb 25 10:57:30 PST 1999
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