Rapid PVST+ Spanning-tree Summary

Rapid-spanning-tree is an enhanced 802.1d standard. The differences:

• Only waits for 3 missed Hello’s instead of 10 Hello’s (maxage timer)

• Transitioning from disabled state to learning state (skipping the Listening state)

• uses some other port types

1. Max Age
   1. Max Age is refreshed every time the port receives a BPDU
   2. PVST
      1.                     i.        non-designated ports will save a BPDU for (default 20 seconds)
      2.                    ii.        If port fails to hear 10 BPDUs in a row
      3.                               i.        Max age expires
      4.                              ii.        port transitions to Listening state
         1. RPVST
            1.                     i.        non-designated ports will save a BPDU for (default 6 seconds)
            2.                    ii.        If port fails to hear 3 BPDUs in a row
            3.                               i.        Max age expires
            4.                              ii.        port transitions to Learning state
2. Forward Delay
   1. 1. time spent in Listening and Learning states (default 15 seconds)
3. Time to transition from blocking to forwarding
   1. PVST
      1.                     i.        Max Age + (2 * Forward Delay) =  (20 seconds) + (2 * 15 seconds) = 50 seconds
   2. RPVST
      1.                     i.        Max Age + (1 * Forward Delay) =  (6 seconds) + (1 * 15 seconds) = 21 seconds