Need help in STP

chinamanchinaman Inactive Imported Users Posts: 167
Hello again and I just want to ask for help regarding STP.
I'm just reviewing my Press book and again I was confused on how STP works. Can you explain to me the blocking and forwarding state.

How many port is in blocking state? and forwarding state.
Just explain to me about root port, designate port and nonroot bridge root port.

one week to go before Intro exam any advice.



  • KGhaleonKGhaleon Member Posts: 1,346 ■■■■□□□□□□
    What don't you understand? There are a lot of websites out there that will inform you and I'm sure someone here will give you the rundown soon enough. VTP and STP are fairly easy topics on the CCNA, so don't get too stressed over it. Just know that the switch ports can be in a Blocking, forwarding, or disabled state.

    Anything not assigned as a root port, designate port or nonroot bridge port is put into the blocking state by default.

    Present goals: MCAS, MCSA, 70-680
  • kplabkplab Member Posts: 101
    KPLAB - Free CCNA, CCNP, and Network+ Study Guides
  • chinamanchinaman Inactive Imported Users Posts: 167
    Nice link, now I understand very well how STP works. So the lowest BID value will be elected as a root bridge and the least cost to the root port is the designated port to all connected segment. And also when there is a topology change it will notify the root bridge when one of the links fail. Correct me if I'm wrong
  • myk_roquemyk_roque Member Posts: 34 ■■□□□□□□□□
    Just remeber the STP processes.

    The first thing is that it must elect the root bridge. STP uses the priority and the Bridge ID for that. All ports on the root switch is forwarding.

    When the root bridge is selected, it seeks out the root ports, at this point it uses the Total Path cost to reach the root bridge for switches. All root ports will be forwarding.

    Next stop is electing the designated ports for non-root port switches which again uses the BID. Designated ports are placed in forwarding.

    All the rest of the ports will be placed in blocking.

    STP is complete and they are all convereged :)

    Off topic, OSPF BR and BDR election chooses the *highest* values for priority and ID.

    All the rest (Like Administrative Distance, STP Root) will be using the lowest values.

    I dunno about you but this has been a cause for a lot of confusion for me. So I jst had to remember what values it has to be compared to. I hope youve locked them all up chinaman. When will your test be?
    “Remember that everyone you meet is afraid of something, loves something, and has lost something”
  • chinamanchinaman Inactive Imported Users Posts: 167
    Thanks MyK_roque, this coming thursday is my intro exam. Actually I'm now getting nervous and getting confused already.
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