Cisco Systems BC-109 manual Configure a Multiport Bridge Using a Virtual Ring

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Configure a Multiport Bridge Using a Virtual Ring

A dual-port bridge is a limitation imposed by IBM Token Ring chips; the chips can process only two ring numbers. If you have a router with two or more Token Ring interfaces, you can work around the two-ring number limitation. You can configure your router as multiple dual-port bridges or as a multiport bridge using a virtual ring.

You can define several separate dual-port bridges in the same router. However, the routers on the LANs cannot have any-to-any connectivity; that is, they cannot connect to every other router on the bridged LANs. Only the routers connected to the dual-port bridge can communicate with one another. Figure 46 shows two separate dual-port bridges (T0-T2 and T1-T3) configured on the same router.

Figure 46 Multiple Dual-Port Bridges

	Token
	Ring
	T1
Token T2	T0 Token
Ring	Ring

T3

Token

Ring

S2323

To configure multiple dual-port source-route bridges, use the following command in interface configuration mode for each Token Ring interface that is part of a dual-port bridge:

Command	Purpose
source-bridgelocal-ring bridge-number target-ring	Enable local source-route bridging on
	a Token Ring interface.

If you want your network to use only SRB, you can connect as many routers as you need via Token Rings. Remember, source-route bridging requires you to bridge only Token Ring media.

Configure a Multiport Bridge Using a Virtual Ring

A better solution for overcoming the two-ring number limitation of IBM Token Ring chips is to configure a multiport bridge using a virtual ring. A virtual ring on a multiport bridge allows the router to interconnect three or more LANs with any-to-any connectivity; that is, connectivity between any of the routers on each of the three LANs is allowed. A virtual ring creates a logical Token Ring internal to the Cisco IOS software, which causes all the Token Rings connected to the router to be treated as if they are all on the same Token Ring. The virtual ring is called a ring group. Figure 47 shows a multiport bridge using a virtual ring.

Configuring Source-Route Bridging BC-111

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Contents SRB Configuration Task List Configuring Source-Route BridgingConfigure a Dual-Port Bridge Configure Source-Route BridgingMultiple Dual-Port Bridges Configure a Multiport Bridge Using a Virtual RingDefine a Ring Group in SRB Context Source-bridge ring-group ring-groupNo source-bridge ring-group ring-group Source-bridge route-cache cbus Configure SRB over FddiEnable SRB and Assign a Ring Group to an Interface Interface fddi slot/portConfigure SRB over Frame Relay Configure Fast-Switching SRB over FddiEnable the Automatic Spanning-Tree Function Limit the Maximum SRB Hops Enable Use of the RIF Configure Bridging of Routed ProtocolsConfigure the RIF Timeout Interval Configure a Static RIF EntryOverview of SR/TLB Following notes and caveats apply to all uses of SR/TLB No source-bridge transparent ring-group fastswitch Enable Bridging between Transparent Bridging and SRBDisable Fast-Switched SR/TLB Enable Translation Compatibility with IBM 8209 BridgesSource-bridge sap-80d5 dsap Enable Token Ring LLC2-to-Ethernet ConversionEnable 0x80d5 Processing Enable Standard Token Ring LLC2-to-Ethernet LLC2 ConversionConfigure NetBIOS Support Source-bridge proxy-netbios-only Specify Timeout and Enable NetBIOS Name CachingSpecify Dead-Time Intervals for NetBIOS Packets Configure the NetBIOS Cache Name LengthEnable NetBIOS Proxying Create Static Entries in the NetBIOS Name CacheConfigure LNM Support Netbios name-cache query-timeout secondsNetbios name-cache recognized-timeout seconds LNM Linking to a Source-Route Bridge on Each Local Ring LAN Network Manager Monitoring and Translating How a Router Works with LNMDisable LNM Functionality Enable Other LRMs to Change Router Parameters Disable Automatic Report Path Trace FunctionApply a Password to an LNM Reporting Link Enable LNM ServersChange Reporting Thresholds Change an LNM Reporting Interval Monitor LNM OperationLnm softerr milliseconds Configure NetBIOS Access Filters Configure NetBIOS Access Filters Using Station NamesSecure the SRB Network Netbios input-access-filter bytes name Configure NetBIOS Access Filters Using a Byte OffsetNetbios access-list host name permit deny pattern Netbios access-list bytes name permit deny offsetConfigure Administrative Filters for Token Ring Traffic Netbios output-access-filter bytes nameFilter Frames by Protocol Type Filter Frames by Vendor Code Filter Source AddressesFilter Destination Addresses Access Expression Example Optimize Access Expressions Configure Access ExpressionsTune the SRB Network Alter Access Lists Used in Access ExpressionsEnable or Disable the Source-Route Fast-Switching Cache Enable or Disable the SSE Establish the Connection Timeout IntervalOptimize Explorer Processing Controlling Explorer Storms in Redundant Network Topologies Configure Proxy Explorers Establish SRB Interoperability with TI MAC FirmwareMac-address ieee-address Monitor and Maintain the SRB Network Report Spurious Frame-Copied ErrorsSource-bridge tcp-queue-max number SRB Configuration ExamplesBasic SRB with Spanning-Tree Explorers Example Dual-Port Source-Route Bridge ConfigurationSRB-Only Example Optimized Explorer Processing Configuration ExampleMultiport SRB Example SRB and Routing Certain Protocols ExampleSRB with Multiple Virtual Ring Groups Example Configuration for Router aRouter a SRB over Fddi Configuration ExamplesSRB over Fddi Fast-Switching Example Configuration for Router BFrad Using SRB over Frame Relay to Connect to a Cisco Router SRB over Frame Relay Configuration ExampleAdding a Static RIF Cache Entry Example Configuration of Router aConfiguration on Router B Configuration on Router CSR/TLB for a Simple Network Example Adding a Static RIF Cache Entry for a Two-Hop Path ExampleBC-154Bridging and IBM Networking Configuration Guide Example of a Bit-Swapped Address SR/TLB with Access Filtering ExampleSpecifying a Static Entry NetBIOS Support with a Static NetBIOS Cache Entry ExampleLNM for a Simple Network Example Wayfarer# show lnm configLNM for a More Complex Network Example NetBIOS Access Filters Example Filtering Bridged Token Ring Packets to IBM Machines Example Shows a router connecting four Token Rings Following access expression would result Creating Access Filters ExampleFast-Switching Example Access Filters ExampleAutonomous Switching Example