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2 Common Mistakes

2 Common Mistakes. Add link cost on receipt of BPDU vs transmit Use receiving port ID vs sender port ID Both are special cases of different Port BPDUs on the same segment… …a mistake!. Add link cost on trasmit. State :

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2 Common Mistakes

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  1. 2 Common Mistakes • Add link cost on receipt of BPDU vs transmit • Use receiving port ID vs sender port ID • Both are special cases of different Port BPDUs on the same segment… • …a mistake! CE 151 - Advanced Networks

  2. Add link cost on trasmit State: • A list of “Port BPDUs” set to the smallest BPDU sent/received on a port. Initialization: • Send BPDU(Root=Me, Cost=0, Sender=Me, …) on each port and update Port BPDUs On receipt of a BPDU: • If BPDU < Port BPDU, update Port BPDU • Add link cost to BPDU cost • For all ports where BPDU < Port BPDU (sort by Root then Cost then Sender…), send: BPDU(Root=BPDU Root, Cost=BPDU Cost, Sender=Me, …) And update the Port BPDU. Periodically update port status: • If smallest (Port BPDU+ link cost) on switch was not sent by me, label port Root • If Port BPDU was sent by me, label portDesignated • Label all other ports Blocked On receipt of data frame on Root or Designated port: • Send out all other Root or Designated ports Not complete… topology changes! CE 151 - Advanced Networks

  3. Correct – add link cost on transmit Root Designated A 1 2 Blocked 5 5 1 1 5 C B 2 2 CE 151 - Advanced Networks

  4. Correct – add link cost on transmit Root Designated A 1 2 Blocked [RootID, RootPathCost, SenderID, PortID]/Status [A,0,A,2] [A,0,A,1] 5 5 1 1 5 C B 2 2 A sends BPDU. CE 151 - Advanced Networks

  5. Correct – add link cost on transmit Root Designated A 1 2 Blocked [RootID, RootPathCost, SenderID, PortID]/Status [A,0,A,2] [A,0,A,1] 5 5 1 1 5 C B 2 2 B & C receive BPDUs. CE 151 - Advanced Networks

  6. Correct – add link cost on transmit Root Designated A 1 2 Blocked [RootID, RootPathCost, SenderID, PortID]/Status 5 5 [A,5,B,2] 1 1 5 C B 2 2 [A,5,C,2] B & C send BPDUs. CE 151 - Advanced Networks

  7. Correct – add link cost on transmit Root Designated A 1 2 Blocked [RootID, RootPathCost, SenderID, PortID]/Status 5 5 [A,5,B,2] 1 1 5 C B 2 2 [A,5,C,2] C receives BPDU. CE 151 - Advanced Networks

  8. Correct – add link cost on transmit Root Designated A 1 2 Blocked [RootID, RootPathCost, SenderID, PortID]/Status 5 5 1 1 5 C B 2 2 CE 151 - Advanced Networks

  9. Correct – add link cost on transmit Root Designated A 1 2 Blocked [RootID, RootPathCost, SenderID, PortID]/Status 5 5 1 1 5 C B 2 2 CE 151 - Advanced Networks

  10. Correct – add link cost on transmit Root Designated A 1 2 Blocked [RootID, RootPathCost, SenderID, PortID]/Status 5 5 1 1 5 C B 2 2 CE 151 - Advanced Networks

  11. Correct – add link cost on transmit Root Designated A 1 2 Blocked [RootID, RootPathCost, SenderID, PortID]/Status 5 5 1 1 5 C B 2 2 NO LOOP! Port BPDUs the same on each segment! CE 151 - Advanced Networks

  12. Incorrect – add link cost on receive Root Designated A 1 2 Blocked 5 5 1 1 5 C B 2 2 CE 151 - Advanced Networks

  13. Incorrect – add link cost on receive Root Designated A 1 2 Blocked [RootID, RootPathCost, SenderID, PortID]/Status [A,0,A,2] [A,0,A,1] 5 5 1 1 5 C B 2 2 A sends BPDU. CE 151 - Advanced Networks

  14. Incorrect – add link cost on receive Root Designated A 1 2 Blocked [RootID, RootPathCost, SenderID, PortID]/Status [A,0,A,2] [A,0,A,1] 5 5 1 1 5 C B 2 2 B & C receive BPDUs. CE 151 - Advanced Networks

  15. Incorrect – add link cost on receive Root Designated A 1 2 Blocked [RootID, RootPathCost, SenderID, PortID]/Status 5 5 [A,5,B,2] 1 1 5 C B 2 2 [A,5,C,2] B & C send BPDUs. CE 151 - Advanced Networks

  16. Incorrect – add link cost on receive Root Designated A 1 2 Blocked [RootID, RootPathCost, SenderID, PortID]/Status 5 5 [A,5,B,2] 1 1 5 C B 2 2 [A,5,C,2] CE 151 - Advanced Networks

  17. Incorrect – add link cost on receive Root Designated A 1 2 Blocked [RootID, RootPathCost, SenderID, PortID]/Status 5 5 1 1 5 C B 2 2 CE 151 - Advanced Networks

  18. Incorrect – add link cost on receive Root Designated A 1 2 Blocked [RootID, RootPathCost, SenderID, PortID]/Status 5 5 1 1 5 C B 2 2 CE 151 - Advanced Networks

  19. Incorrect – add link cost on receive Root Designated A 1 2 Blocked [RootID, RootPathCost, SenderID, PortID]/Status 5 5 1 1 5 C B 2 2 CE 151 - Advanced Networks

  20. Incorrect – add link cost on receive Root Designated A 1 2 Blocked [RootID, RootPathCost, SenderID, PortID]/Status 5 5 1 1 5 C B 2 2 LOOP! Port BPDUs differ on each segment! CE 151 - Advanced Networks

  21. Use sender port ID • Switches exchange messages describing their best paths to the root • These messages are called Bridge Protocol Data Units • Root ID, Root Path Cost, Sender ID, Port Priority, Port ID • Set by sendingswitch (Sender ID, Port Priority and ID of sender)! • Sorted by fields, in order (Root ID, then Path Cost, etc.). • Root port is port with “best” path to root (smallest BPDU)on switch • Root switch doesn’t have a root port. • Designated port is port with “best” path to root (smallest BPDU)on link • All other ports are Blocked • The Root and Designated ports form the switches into a tree. CE 151 - Advanced Networks

  22. Correct – Sender Port ID Root 2 Designated 1 5 A B 5 2 1 Blocked CE 151 - Advanced Networks

  23. Correct – Sender Port ID Root [A,0,A,1] 2 Designated 1 5 A B 5 2 1 Blocked [A,0,A,2] A sends BPDUs. [RootID, RootPathCost, SenderID, PortID]/Status CE 151 - Advanced Networks

  24. Correct – Sender Port ID Root [A,0,A,1] 2 Designated 1 5 A B 5 2 1 Blocked [A,0,A,2] B receives BPDUs. [RootID, RootPathCost, SenderID, PortID]/Status CE 151 - Advanced Networks

  25. Correct – Sender Port ID Root 2 Designated 1 5 A B 5 2 1 Blocked [RootID, RootPathCost, SenderID, PortID]/Status CE 151 - Advanced Networks

  26. Correct – Sender Port ID Root 2 Designated 1 5 A B 5 2 1 Blocked [RootID, RootPathCost, SenderID, PortID]/Status CE 151 - Advanced Networks

  27. Correct – Sender Port ID Root 2 Designated 1 5 A B 5 2 1 Blocked [RootID, RootPathCost, SenderID, PortID]/Status Port BPDUs the same on each segment! A controls port. CE 151 - Advanced Networks

  28. Correct – Sender Port ID Root 2 Designated 1 5 A B 5 2 1 Blocked CE 151 - Advanced Networks

  29. Correct – Sender Port ID Root [A,0,A,1] 2 Designated 1 5 A B 5 2 1 Blocked [A,0,A,2] A sends BPDUs. [RootID, RootPathCost, SenderID, PortID]/Status CE 151 - Advanced Networks

  30. Correct – Sender Port ID Root [A,0,A,1] 2 Designated 1 5 A B 5 2 1 Blocked [A,0,A,2] B receives BPDUs. [RootID, RootPathCost, SenderID, PortID]/Status CE 151 - Advanced Networks

  31. Correct – Sender Port ID Root 2 Designated 1 5 A B 5 2 1 Blocked [RootID, RootPathCost, SenderID, PortID]/Status CE 151 - Advanced Networks

  32. Correct – Sender Port ID Root 2 Designated 1 5 A B 5 2 1 Blocked [RootID, RootPathCost, SenderID, PortID]/Status CE 151 - Advanced Networks

  33. Correct – Sender Port ID Root 2 Designated 1 5 A B 5 2 1 Blocked [RootID, RootPathCost, SenderID, PortID]/Status Port BPDUs differ on each segment! A doesn’t control port. CE 151 - Advanced Networks

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