Switches/Bridge STP

[telcomwork]

I'm studying for my CCNA and was wondering if someone could clear up some confusion I have with bad explanation in a CCNA study guide. In terms of root ports and Designated Ports, I understand that Root Bridge Ports are called Designated ports, but in a Network example they have a designated port off a non root bridge. Is this accurate? Also what's the diffrence between root ports and Designated ports? Here is the information I have from the book...

Root Port - port with the lowest cost (as determined by a links bandwidth) to the root bridge which send and recives traffic.

Designated Port - A port determined to have the lowest cost path to the root bridge.

By definition I don't see a diffrence. Any help explaining this more thoughly is much appreciated.

 

[wybnormal]

Here is the short version.

Root port- port with closest to the root bridge and the lowest cost back to the root bridge.. so far so good.

Designated port- this is the port that advertises the lowest cost back to the root bridge. If two ports have the same cost back to the root bridge, then the bridgeID will be the tie breaker.

This is a concept that cries out for a picture.

This presentation is not bac.. go to slide 15 for the picture.

MikeS
Find me at

http://www.packetattack.com

"Take advantage of the enemy's unreadiness, make your way by unexpected routes, and attack unguarded spots."
Sun Tzu

 

[telcomwork]

Thank you very much!!!!!!!

 

[telcomwork]

Few more question if you don't mind, so designated ports don't have to be directley connected to the root bridge, there can be designated and root ports on diffrent segments to use other switches to get to the root bridge, correct? I'm assuming there are designated and root ports off diffrent segments. Also I'm haivng a hard time finding the slide to use as an example off the packetattack web sight. Thanks for all your help.

 

[telcomwork]

So there can be root and designated ports on diffrent segments point back to the segment with the root bridge?

I can't find the information your referenced, at packetattack. Where is slide 15?

 

[wybnormal]

My mistake... I forgot to cut and paste in the URL

http://www.kulnet.kuleuven.ac.be/doc/kulnetdoc/

kulnetdoc-2001-5.pdf

Watch for wrap on the link.

In answer to your question, yes, there can and will be root ports and designated ports on each segment pointing back to the root bridge.

MikeS
Find me at

http://www.packetattack.com

"Take advantage of the enemy's unreadiness, make your way by unexpected routes, and attack unguarded spots."
Sun Tzu

 

[telcomwork]

Thanks again for your help!