Example: air traffic controller

SPANNING TREE · P ART 1 - PacketLife.net

Jeremy PART1 BPDU FormatProtocol ID16 SPANNING tree ProtocolsAlgorithmLegacy STPPVSTD efined ByInstancesTrunkingPVST+RPVST+MSTL egacy STCiscoPer VLANISLL egacy STCiscoPer , ISLR apid STCiscoPer , ISLR apid , , ISLRSTPR apid , tree Instance ComparisonSTPCABAll VLANsxRootPVST+CABVLAN 1 VLAN 10 VLAN 20 VLAN 30xx xxVLAN 1,10 Root VLAN 20,30 RootMSTCABMSTI 0 (1, 10)MSTI 1 (20, 30)x xMSTI 0 Root MSTI 1 RootFieldBitsVersion8 BPDU Type8 Flags8 Root ID64 Root Path Cost32 Bridge ID64 Port ID16 Message Age16 Max Age16 Hello Time16 Forward Delay16 SPANNING tree +RPVST+ Costs4 Mbps250 BandwidthCost10 Mbps10016 Mbps6245 Mbps39100 Mbps19155 Mbps14622 Mbps61 Gbps410 Gbps2 Default TimersHelloForward DelayMax Age2s15s20sPort StatesDisabledDiscardingLegacy STRapid STBlockingListeningLearningLearningForwa rdingForwardingIEEE Deprecated legacy STP standardIEEE Introduced RSTPIEEE Replaced legacy STP with RSTPIEEE Introduced MSTIEEE Added MST to Per-VLAN implementation of legacy STPPVST+ Added trunking to PVSTRPVST+ Per-VLAN implementation of RSTPPort RolesRootRootLegacy STRapid STDesignatedDesignatedBlockingAlternateB ackupSpanning tree OperationDetermine root bridgeThe bridge advertising the lowest bridge ID becomes the root bridgeSelect root portEach

packetlife.net by Jeremy Stretch v3.0 IEEE Cisco SPANNING TREE · P ART 1 BPDU Format Protocol ID 16 Spanning Tree Protocols Algorithm Legacy STP PVST Defined By Instances Trunking

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Transcription of SPANNING TREE · P ART 1 - PacketLife.net

1 Jeremy PART1 BPDU FormatProtocol ID16 SPANNING tree ProtocolsAlgorithmLegacy STPPVSTD efined ByInstancesTrunkingPVST+RPVST+MSTL egacy STCiscoPer VLANISLL egacy STCiscoPer , ISLR apid STCiscoPer , ISLR apid , , ISLRSTPR apid , tree Instance ComparisonSTPCABAll VLANsxRootPVST+CABVLAN 1 VLAN 10 VLAN 20 VLAN 30xx xxVLAN 1,10 Root VLAN 20,30 RootMSTCABMSTI 0 (1, 10)MSTI 1 (20, 30)x xMSTI 0 Root MSTI 1 RootFieldBitsVersion8 BPDU Type8 Flags8 Root ID64 Root Path Cost32 Bridge ID64 Port ID16 Message Age16 Max Age16 Hello Time16 Forward Delay16 SPANNING tree +RPVST+ Costs4 Mbps250 BandwidthCost10 Mbps10016 Mbps6245 Mbps39100 Mbps19155 Mbps14622 Mbps61 Gbps410 Gbps2 Default TimersHelloForward DelayMax Age2s15s20sPort StatesDisabledDiscardingLegacy STRapid STBlockingListeningLearningLearningForwa rdingForwardingIEEE Deprecated legacy STP standardIEEE Introduced RSTPIEEE Replaced legacy STP with RSTPIEEE Introduced MSTIEEE Added MST to Per-VLAN implementation of legacy STPPVST+ Added trunking to PVSTRPVST+ Per-VLAN implementation of RSTPPort RolesRootRootLegacy STRapid STDesignatedDesignatedBlockingAlternateB ackupSpanning tree OperationDetermine root bridgeThe bridge advertising the lowest bridge ID becomes the root bridgeSelect root portEach

2 Bridge selects its primary port facing the rootSelect designated portsOne designated port is selected per segmentBlock ports with loopsAll non-root and non-desginated ports are blocked1234 IEEE Most recent revision20+ Jeremy PART2 PVST+ and RPVST+ Configurationspanning- tree mode {pvst | rapid-pvst}! Bridge priorityspanning- tree vlan 1-4094 priority 32768! Timers, in secondsspanning- tree vlan 1-4094 hello-time 2spanning- tree vlan 1-4094 forward-time 15spanning- tree vlan 1-4094 max-age 20! PVST+ Enhancementsspanning- tree backbonefastspanning- tree uplinkfast! Interface attributesinterface FastEthernet0/1spanning- tree [vlan 1-4094] port-priority 128spanning- tree [vlan 1-4094] cost 19! Manual link type specificationspanning- tree link-type {point-to-point | shared}! Enables PortFast if running PVST+, or! designates an edge port under RPVST+ SPANNING - tree portfast! SPANNING tree protectionspanning- tree guard {loop | root | none}!

3 Per-interface togglingspanning- tree bpduguard enablespanning- tree bpdufilter enableTroubleshootingshow SPANNING - tree [summary | detail | root]show SPANNING - tree [interface | vlan]MST Configurationspanning- tree mode mst! MST Configurationspanning- tree mst configurationname MyTreerevision 1! Map VLANs to instancesinstance 1 vlan 20, 30instance 2 vlan 40, 50! Bridge priority (per instance) SPANNING - tree mst 1 priority 32768! Timers, in secondsspanning- tree mst hello-time 2spanning- tree mst forward-time 15spanning- tree mst max-age 20! Maximum hops for BPDU sspanning- tree mst max-hops 20! Interface attributesinterface FastEthernet0/1spanning- tree mst 1 port-priority 128spanning- tree mst 1 cost 19 Bridge ID FormatPriSys ID ExtMAC Address41248 System ID Extension12-bit value taken from VLAN number (IEEE )Priority4-bit bridge priority (configurable from 0 to 61440 in increments of 4096)MAC Address48-bit unique identifierPath Selection1 Bridge with lowest root ID becomes the root234 Prefer the neighbor with the lowest cost to rootPrefer the neighbor with the lowest bridge IDPrefer the lowest sender port IDOptional PVST+ EhancementsPortFastEnables immediate transition into the forwarding state (designates edge ports under MST)

4 UplinkFastEnables switches to maintain backup paths to rootBackboneFastEnables immediate expiration of the Max Age timer in the event of an indirect link failureSpanning tree ProtectionRoot GuardPrevents a port from becoming the root portBPDU GuardError-disables a port if a BPDU is receivedLoop GuardPrevents a blocked port from transitioning to listening after the Max Age timer has expiredBPDU FilterBlocks BPDUs on an interface (disables STP)RSTP Link TypesPoint-to-PointConnects to exactly one other bridge (full duplex)SharedPotentially connects to multiple bridges (half duplex)EdgeConnects to a single host; designated by PortFastshow SPANNING - tree mst [.]


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