Passed ccent today i have a question about spanning tree protocol

jcarrillo26

I PASSED THE ICND1 EXAM TODAY WITH A 881 AND NOW WORKING ON THE ICND2 EXAM. I KNOW THAT SPANNING TREE IS USED FOR A REDUNDANT DESIGN SO THERE IS NOT A SWITCHING LOOP FOREVER BECAUSE UNLIKE LAYER 2 LAYER 3 HAS A TTL THAT WILL STOP ROUTING LOOPS. SO THAT SAID I KNOW WHAT THE PURPOSE OF STP IS USED FOR BUT I HAVE A HARD TIME UNDERSTANDING THE LAST PART THAT IS USED BY SPANNING TREE. I KNOW THE FIRST PART OF SPANNING TREE IS TO NEGOTIATE WHO THE ROOT BRIDGE IS WITH BDPU's ONCE THAT THE ROOT IS ESTABLISHED. IT DETERMINES WHAT PORTS ON NON ROOT SWITCH IS THE BEST WAY TO GET TO THE ROOT SO ROOT PORTS NEED TO BE ESTABLISHED ON NON ROOT SWITCHES USING COST. THE LAST PART IS HOW DOES IT NEGOTIATE ON THE SWITCHES WHICH PORT IS GOING TO BE IN A BLOCKING STATE, LIKE WHICH PORT ON THE NON ROOT SWITCH IS BLOCKING WHAT ON WHAT PORT. IS IT A NEGOTIATION THAT GOES ON WITH THE NON ROOT SWITCHES AND DETERMINE BASED ON COST? PRIORITY WITH BDPUS SENT TO EACHOTHER? THANK YOU FOR YOUR FEEDBACK I REALLY APPRECIATE IT.

late_collision

Yes, there is an election process based on the lowest root bridge id, lowest root path cost, lowest sender bridge id, and lowest port id!!!

jcarrillo26

hey thanks for the reply sorry if i maybe repeating myself but since the root election process has been done. it elects the root ports and then there is an election with the other two switches or how many switches there are saying i have a priority over you so your port is going to be in a blocking state? thanks again.

late_collision

Rather than type it all out again, here is a link to a post I made about 2 months ago covering STP convergence

http://www.techexams.net/forums/ccna-ccent/97465-stp-question.html#post822040

Note: Scroll up to find the topology that my post was referencing.

jcarrillo26

thanks i really appreciate it. that is an awesome post!

10Linefigure

Congrats on the pass!

jcarrillo26

hey thanks man i am working on the icnd2 right now plan on taking it next week or so i am pretty confident i am going to pass

OfWolfAndMan

Congrats on the pass man! Since everyone already covered it, just remember this: Bridge ID, Mac address then port number (The lower the number the more preferred of. course) in that order. Also, you'll encounter pvst (per vlan spanning tree), and rstp in your future studies. Make sure you know those as well! Good luck!

jcarrillo26

hey thanks for the feedback i really appreciate it! i have covered pvst and rstp correct me if i am wrong but the only difference is that you are dealing with multiple vlans instead of one vlan. also the convergence time is quicker with the portfast command that can be applied to the end devices.

jcarrillo26

Would you know the purpose of vlans in spanning tree on the command of show interface trunk ?

jeffgibbs

If I understand your question I am pretty sure its showing you what Vlans are allowed on the trunk. Remember sometimes a Vlan will be pruned....