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Rapid Spanning Tree

Rapid Spanning Tree. CK NG Technical Marketing. Speaker 2006/XX/XX. Speaker 2007/XX/XX. WWW.Edge-Core.com. www.Edge-Core.com. Why need STP ?. Preventing undesirable loops in the network. Provides path redundancy. Only one active path can exist between two stations.

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Rapid Spanning Tree

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  1. Rapid Spanning Tree CK NG Technical Marketing Speaker 2006/XX/XX Speaker 2007/XX/XX WWW.Edge-Core.com www.Edge-Core.com

  2. Why need STP ? • Preventing undesirable loops in the network. • Provides path redundancy. • Only one active path can exist between two stations.

  3. What STP Can Do ? • Automatically Detect Loop on the Network. • Calculate path capacities and then place high-cost ( or lowest capacity) links in a backup state automatically and deterministically

  4. Looping Broadcast Multicast Unknown Unicast • Broadcasts, Multicast or Unknown Unicast lead to Broadcast storm in the network Desktop PC ES4524D ES4524D ES4524D ES4524D

  5. STP BPDU Format Protocol ID 2 octets Ver2 RSTP Version 1 octet 00 Configuration 80 TCN BPDU Type 1 octets 01 BPDU Flags 1 octets 2-byte priority 6-byte MAC Root ID 8 octets Cost of Path Cost of the path to root 4 octets Bridge ID 8 octets Port ID 2 octets Message Age Root Message Age =0 2 octets 2 octets Max Age 20 Seconds 2 Seconds 2 octets Hello Time 2 octets Forward Delay 15 Seconds Version 1 Length Total length = 36 bytes

  6. RSTP BPDU Format Protocol ID 2 octets Ver2 RSTP Version 1 octet TCA Agreement Fowarding Learning Port Role Proposal TC 0 1 2 3 4 5 6 7 BPDU Type 02 RST BPDU 1 octets BPDU Flags 1 octets 2-byte priority 6-byte MAC Root ID 8 octets Cost of Path Cost of the path to root 4 octets Bridge ID 8 octets Port ID 2 octets Message Age Root Message Age =0 2 octets 2 octets Max Age 20 Seconds 2 Seconds 2 octets Hello Time 2 octets Forward Delay 15 Seconds Version 1 Length Total length = 36 bytes

  7. Bridge Port States No Link Disabled Blocking 20 s Max Age Listening Fast Spanning Tree 15 s Forward Delay 1s Before Forwarding Learning 15 s Forward Delay Forwarding

  8. STP Port States Receive BPDU Transmit BPDU Learn Address Forward Data Disabled - - - - Blocking a - - - Listening a a - - Learning a a a - Forwarding a a a a

  9. Root Bridge Selection • At startup each switch assumes itself as root bridge and set bridge ID equal to Root ID in the BPDU it send out • Bridge ID consist of 2-bytes priority and 6-bytes MAC Address • Priority range 0-65535 Default 32,768 or 0x8000 • Bridge with highest priority (lowest value) will become root bridge • If all devices have the same priority, the bridge with lowest MAC address becomes the root bridge

  10. Root Selection Priority ID MAC Address 32768. 0030F1DFA020 is Root Path cost: 0 BPDU Bridge ID I am the root 32768.0030F1BED860 SW1 Boot up first SW4 SW2 ES4626-SFP 32768.0030F1DFA020 32768.0030F1F91240 SW3 Designated Port : DP Root Port : RP ES4626-SFP 32768.0030F1DE9E60

  11. Root Selection Priority ID MAC Address 32768. 0030F1BED860 is Root Path cost: 0 BPDU Root Bridge ID No, You are not the Root I am the root 32768.0030F1BED860 SW1 SW4 SW2 32768.0030F1DFA020 32768.0030F1F91240 SW3 Designated Port : DP Root Port : RP 32768.0030F1DE9E60

  12. Root Port • The port offers the lowest cost path to the root. • The port which receivesBPDU from designated port • Root Port Selection • Lowest Root Path Cost>Highest Designated Bridge>Highest Designated Port ID>Highest Port ID

  13. Designated Port • The bridge which designated port attached offer the lowest cost to the root for the LAN. • Designated port regenerates BPDU to the downstream bridge • Designated Port Selection • Lowest Designated Cost for the LAN>Highest Designated Bridge>Highest Port ID

  14. Designated Bridge • The Bridge which designated port attached for the LAN

  15. Blocked Port • The port neither the root port nor the designated will become blocked port. • Blocked port doesn’t forward packet. • Blocked port receives BPDU from the designated port but doesn’t forward it

  16. Path Cost Half Path Cost Full Trunk Link Speed 10Mbps 100 2,000,000 95 1,000,000 90 500,000 (STP) (RSTP) 100Mbps 19 200,000 18 100,000 15 50,000 (STP) (RSTP) (STP) 1Gbps 5 4 10,000 3 5,000 (RSTP) 10Gbps 2 2 1000 2 500 (STP) (RSTP)

  17. Port Role Priority ID MAC Address 32768.0030F1BED860 is Root Path cost: 0 32768.0030F1BED860 is Root Path cost: 0 32768.0030F1BED860 is Root Path cost: 10,000 32768.0030F1BED860 is Root Path cost: 10,000 BPDU BPDU BPDU BPDU Root Smallest Bridge ID 32768.0030F1BED860 SW1 DP DP 10,000 10,000 RP RP SW4 SW2 32768.0030F1DFA020 32768.0030F1F91240 DP Designated Bridge DP Designated Bridge 10,000 10,000 SW3 Alternate Port RP Designated Port : DP Root Port : RP 32768.0030F1DE9E60

  18. Equal Port Cost Priority ID MAC Address 32768.0030F1BED860 is Root Path cost: 0 32768.0030F1BED860 is Root Path cost: 0 32768.0030F1BED860 is Root Path cost: 10,000 32768.0030F1BED860 is Root Path cost: 10,000 BPDU BPDU BPDU BPDU Root Smallest Bridge ID 32768.0030F1BED860 SW1 DP DP 10,000 10,000 RP RP SW4 SW2 32768.0030F1DFA020 32768.0030F1F91240 DP Designated Bridge DP Designated Bridge 10,000 10,000 SW3 Alternate Port RP • Received BPDUs from 2 ports Telling • 32768.0030F1BED860 is Root • Loop • Same Path cost to root 20,000 • 32768.0030F1DFA020<32768.0030F1F91240 Designated Port : DP Root Port : RP 32768.0030F1DE9E60

  19. Lower Path Cost Priority ID MAC Address 32768.0030F1BED860 is Root Path cost: 0 32768.0030F1BED860 is Root Path cost: 0 32768.0030F1BED860 is Root Path cost: 10,000 32768.0030F1BED860 is Root Path cost: 10,000 BPDU BPDU BPDU BPDU Root Smallest Bridge ID 32768.0030F1BED860 SW1 DP DP 10,000 10,000 RP RP SW4 SW2 32768.0030F1DFA020 32768.0030F1F91240 DP Designated Bridge DP Designated Bridge 100M Full 100,000 10,000 SW3 Alternate Port RP • Received BPDUs from 2 ports Telling • 32768.0030F1BED860 is Root • Loop • Smaller Path cost to root 20,000 Designated Port : DP Root Port : RP 32768.0030F1DE9E60

  20. Changing Priority ID Priority ID 32768.0030F1BED860 SW1 RP DP 10,000 10,000 Root DP RP SW4 SW2 32768.0030F1DFA020 4096.0030F1F91240 DP Alternate Port 10,000 10,000 SW3 DP RP Designated Port : DP Root Port : RP 32768.0030F1DE9E60

  21. Port ID Priority ID Port ID Priority ID 32768.0030F1BED860 SW1 RP 10,000 RP 128.25 DP Alternate Port Root DP 10,000 DP DP RP 128.26 SW4 SW2 32768.0030F1DFA020 4096.0030F1F91240 DP Alternate Port 10,000 10,000 SW3 DP RP Designated Port : DP Root Port : RP 32768.0030F1DE9E60

  22. RSTP • RSTP provides rapid convergence of the spanning tree in less than 1 second. • Provides rapid recovery of connectivity following the failure of a Bridge, Bridge Ports, or a LAN. • A new Root Port can transit rapidly to the Forwarding Port State. • The use of explicit acknowledgements between Bridges allow Designated Ports to transit rapidly to the Forwarding Port State. • RSTP allows Bridge Ports connected to a LAN segment that is at the edge of the Bridged LAN to be configured to transit directly to Forwarding State

  23. Rapid Convergence • Edges ports—A port configured as an edge port will immediately transit to the forwarding state after link up • Root ports—A new root port will transit immediately to forwarding state and the old root port will be blocked • Point-to-point links—A port connect to another switch via a point-point-link will become designated port and will negotiate a rapid transition with the other port by using proposal-agreement handshake to ensure a loop-free topology

  24. RSTP-Edge Port Priority ID Desktop PC 32768.0030F1BED860 Edge Port SW1 RP 10,000 RP 128.25 DP Alternate Port Root DP 10,000 DP DP 128.26 RP SW4 SW2 32768.0030F1DFA020 4096.0030F1F91240 DP Alternate Port 10,000 10,000 SW3 DP RP Designated Port : DP Root Port : RP 32768.0030F1DE9E60

  25. Prevent Looping PSTN Notebook IP Phone Desktop PC IP Cam Vlan 3 Vlan 2 Internet SW1 IP-PBX Router SW4 SW2 SW3 NAS IP-TV Server Vlan 4 Vlan 5

  26. Redundant Path PSTN Notebook IP Phone Desktop PC IP Cam Vlan 3 Vlan 2 Internet SW1 IP-PBX Router SW4 SW2 SW3 NAS IP-TV Server Vlan 4 Vlan 5

  27. SW1

  28. SW1 Port 23

  29. SW2

  30. SW2 Port 24

  31. Multiple Spanning Tree CK NG Technical Marketing Speaker 2006/XX/XX Speaker 2007/XX/XX WWW.Edge-Core.com www.Edge-Core.com

  32. MSTP • Behaviors • MSTP uses RSTP for rapid convergence to provide loop-free network and redundant path • MSTP enables VLANs to be grouped into a spanning-tree instance, with each instance having a spanning-tree topology, provides multiple forwarding paths for data traffic and enables load balancing

  33. MSTP-STP Per VLAN PSTN Notebook MST1: VLAN2,3 MST2: VLAN4,5 MST1 Priority:4096 MST2 Priority:61440 IP Phone Desktop PC IP Cam Vlan 3 Vlan 2 Internet SW1 IP-PBX Router SW4 SW2 SW3 MST1: VLAN2,3 MST2: VLAN4,5 MST1 Priority:61440 MST2 Priority:4096 NAS IP-TV Server Vlan 4 Vlan 5

  34. MSTP-Load balance PSTN Notebook MST1: VLAN2,3 MST2: VLAN4,5 MST1 Priority:4096 MST2 Priority:61440 IP Phone Desktop PC IP Cam Vlan 3 Vlan 2 Internet SW1 IP-PBX Router SW4 SW2 SW3 MST1: VLAN2,3 MST2: VLAN4,5 MST1 Priority:61440 MST2 Priority:4096 NAS IP-TV Server Vlan 4 Vlan 5

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