Priscilla, In the attachment (Cisco CCNA Exam Guide #640-507 Certification Guide: ISBN 0-7357-0971-8), page 167 - 168, the authors seem to indicate that CBPDUs are sent from blocked ports! The ability for CBPDUs to be sent out of blocked port seems to a determinant factor for the Spanning Tree to be recomputed after a topology change ....
Here is a word by word copy of the passage. The part I have problem about is the one with (!!!!!!) Thanks! Pierre-Alex --(e0)Bridge-1 (e1)-- (e0)Bridge 5(e1)---(e1) Bridge 4 (e0)---(e1)Bridge 3 (e0)---(e1)Bridge 2 (e0)---> (To bridge 1 e0) Cost advertised by B2 is 100 Cost advertised by B3 is 200 Cost advertised by B5 is 10 Blocked port: Bridge 3, port e1 Bridge 5's E1 port fails...Only Bridge 4's MaxAge expires. The other bridges are still receiving CBPDUs on their root ports. After MaxAge expires, Bridge 4 will decide the following: Step 1 My E1 port is no longer my root port Step 2 The same root bridge is being advertised in a CBPDU on my E0 port (!!!!!) Step 3 No other CBPDUs are being received Step 4 My best path (and the only path, in this case) to the root is out of my E0 port; therefore, my root port is now E0.) Step 5 Because no other CBPDUs are entering my E1 port, I must be the designated bridge on that segment. So, I will start sending CBPDUs on E1, addming my E0 port cost (10) to the cost of the CBPDU received in the CBPDU entering E0 (200) for a total of 210 (!!!!!!) >>>>> Kind Regards, Pierre-Alex Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=36691&t=36559 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
