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CCNA Exam: Spanning-tree designated port role

Posted on 2009-04-27
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Hi,

1) This is related to the CCNA Exam.
2) It is discussed in one of the prep test.
3) My questions: [You can give the "links" (if any) after you provide your own wordings please]: i) What does the meaning of "Spanning-tree designated Port Role" in a network?, 2) Provide the examples if you can please
4) Thank you

Tjie
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Question by:tjie
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lrmoore earned 1200 total points
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Root port is a Single port that sends and receives traffic from a switch to and from Root Bridge - Lowest cost path to Root Bridge.
http://www.cisco.com/univercd/cc/td/doc/product/rtrmgmt/sw_ntman/cwsimain/cwsi2/cwsiug2/vlan2/stpapp.htm

It would be easier for us to help you if you provide some level of your own understanding, and what exactly you do not understand
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by:Don Johnston
Don Johnston earned 800 total points
ID: 24249534
Ports on a 802.1d spanning tree switch/bridge will be in one of 5 states (or roles):

Designated (forwarding) - BPDU's go out
 Root (forwarding) - Lowest cost BPDU's come in
Non-Designated (non-forwarding) - Higher cost BPDU's come in
Listening (non-forwarding) - Transitional (learning the topology)
Learning (non-forwarding) - Transitional (clearing the MAC address table)

A designated port is forwarding port that BPDU's go out of. So in a typical topology, every port on a root bridge is a designated port. On a downstream switch, the port that is receiving the lowest cost BPDU is the root port. If there are no loops, then all the other ports on that switch will be designated ports.



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