STP Exercise #1 Solution

Aaron Conaway from aconaway.com walks through a small network to figure out how spanning tree will calculate the root bridge, root ports, designated ports, and blocked ports.

Category:

Science & Technology

Tags:

• aconaway.com
• spanning
• tree
• root
• bridge
• designated
• port
• blocked
• ports
• stp
• ccnp
• switch
• 642-813

[Calafan87]

oh and how do you add mac addresses with a lot of numbers and letters i think i know but just to be sure for my second time around at the ccna

[aconaway1]

@Calafan87 The switches come with built-in MAC addresses, so there's no need to add any.  :)

[hecticCow]

Hey nice vid, I have a question though. If i am on your switch A (The non root bridge) and do the command show spanning tree. How can I tell just from that print out which switch is the root bridge.

Scenario is I have the topology but only access to switch A. thx

[aconaway1]

@hecticCow The first few lines of the output of "show spanning-tree" will show the MAC address of the root bridge. You can't get a name or IP from that output, though, so you'll need to check documentation or do a layer-2 trace (show mac address-table xxxx.xxxx.xxxx) to find it.

[aconaway1]

Thanks, Comblues2000. I found that out right after I published the video. :)

[wa3ar1]

exellent tutorial ! the best i found so far , thanks !!

[tyler361549]

To change path cost:

conf t

int fa0/1

spanning-tree vlan 1 cost 2

[chellerik]

im confused about root bridge id... 4th tie breaker... but twas good.. i understand it more with your video

thanks

[VEG4able]

talking about designated ports, you have 4 tie breakers! But what do you mean with "Root Bridge ID"? I'm confused because you use the Bridge ID (BID) as the 3rd tie breaker o.Ô please help me out

[lupineye]

Thanks! It have been 10 years since I learned network in college. I understand very clearly. Perfect!

[dameskid]

@sirchristoph

Hear exactly what your saying mate, i have read the ICND2 cisco press chapter several times but still cannot grasp it....

[Calafan87]

nice vid man failed my ccna test today :-( ran out of time.

[donnicos]

This really helped me understand the rationale behind the blocking of ports. Good work!