Spanning Tree Protocol Advanced

"different implementations start to work together, they are compatible and backwards compatible."

• IEEE 802.1d can take 50 sec to converge
  • If there is a topology change, something happens, it can take up to 50 secs
  • STP running across all your entire environment (one for all VLANS)
  • 1 root for organization
• 802.1w converges faster
  • "Wapid" spanning tree (faster)
  • Depends on what caused the fault.
  • Uses handshakes Instead of timers
  • Responds to change within 6 sec
  • Can reconverge in milliseconds of a physical link failure
  • We have a backup path.
    • An alternate path that speeds up convergence
• Cisco RPVST+
  • 802.1w once per VLAN
    • If you have 50 VLANs, you have 50 STP processes.
  • Gives you the ability to create 50 different roots
  • Proprietary
  • MSTP is the standardized version.
    • Multi-Instance Spanning Tree.

RTP Port Cost

RTP Port States

RSTP Port Roles

• A suboptimal BPDU is a 2nd place on the best path decision (The second best optimal forwarding path)

Multi-Instance Spanning Tree (MSTP)

• Open standard base successor to the original 802.1d
• Regular spanning tree may have aggregate links unused
• MSTP creates instances
• Example:
  • INST1
    • VLANs
      • 10,20,30
  • INST2
    • VLANs
      • 40,50,60
• Attach VLANs to a different spanning tree process.
  • For each instance tell the VLANs which is the root switch