Spanning-Tree Reconvergence

Lessons Discussion
6

Hi Laz,

thanks a lot for your answer!

  1. I thought it might be faster for the root bridge to send a BPDU with the TC bit set right away when it realizes that a link is down, instead of waiting to hear from other switches in the network through a TCN and then sending the BPDU with the TC set.

  2. Got it

I have two more questions.

  1. Just read the “Spanning-Tree UplinkFast” article and at one point the ND port changes to become the new root port, but it only goes through listening/learning/forwarding. I thought a ND equals a blocking port and thus needs to wait 20sec before starting the listening/learning/forwarding process!?

  2. The last part describes that even though the old root port is active again the switch does not change to that port right away. Why not? Is that a behavior caused by Uplinkfast or is it normal?
    Because the best BPDU is received on that port so why does it not change?
    Does it have to do that the port on SW1 needs 50sec to become active?

Thanks a lot for your help!