Spanning Tree Protocol: RSTP Port States

RSTP has been reworked to classify 3 port states as opposed to the 5 port states normal STP operates with.

802.1d states (STP)

  • Disabled
  • Blocking
  • Listening
  • Learning
  • Forwarding

802.1w states (RSTP)

  • Discarding
  • Learning
  • Forwarding

In 802.1w Discarding and Forwarding are the stable states, while Learning is the only transitory state.

Discarding State – basically means that the port is not forwarding frames nor is it receiving frames.  any frames that are transmitted to this port the MAC is not learned.  A port in a discarding state will still continue to process BPDUs and send/receive frames for inter-switch signaling protocols like DTP, VTP, CDP, LLDP, PAgP, LACP, or LOOP…this is also the default state for when a port first turns up.

Learning State – Same operations done as in 802.1d, port is not forwarding frames however the frames it is receiving it is learning the MAC addresses of those frames as they enter the interface.

Forwarding State – Same operations as in 802.1d ports that are in this state are actively transmitting and receiving any and all frames passed through its interface.

rstpportstates

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