STP/RSTP election process

Just a quick reminder on STP election process (thanks to Dmitry Figol):

  1. Choose Root bridge:
    1. lowest Bridge ID (priority + system mac)
    2. all ports on a Root bridge are designated
  2. Choose Root port on each non-root bridge:
    1. lowest path cost to the root
    2. lowest neighbor Bridge ID
    3. lowest neighbor’s Port ID (port priority + internal port number)
    4. lowest local Port ID (port priority + internal port number)
  3. Choose Designated port on each segment.
    1. bridge with the lowest root path cost
    2. bridge with the lowest Bridge ID
    3. interface with the lowest Port ID
  4. All other ports are non-designated/blocking

Roman Dodin

Network engineer at Nokia
Eagerness to learn multiplied by passion to share.
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