This blog was originally started to better help me understand the technologies in the CCIE R&S blueprint; after completing the R&S track I have decided to transition the blog into a technology blog.

CCIE #29033

This blog will continue to include questions, troubleshooting scenarios, and references to existing and new technologies but will grow to include a variety of different platforms and technologies. Currently I have created over 185 questions/answers in regards to the CCIE R&S track!! Note: answers are in the comment field or within "Read More" section.

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Tuesday, April 27, 2010

Question 44

How do you modify the max-age of a BPDU and what is its purpose?
Posted by Packets Analyzed at 9:17 PM
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1 comments:

Packets Analyzed said...

BDPU (Bridge Protocol Data Units) - is sent and recieved at regular intervals and are not forwarded by the switch but are used to create a loop free path. BPDU's contain the following information
-Switch MAC address
-Switch priority
-Port priority
-Path Cost
This information is used to elect a root bridge, root ports, and designated ports to ensure a loop free topology. When there are multiple ports on a switch that can form a loop, spanning-tree will block these ports based on port priority and port cost preventing the loop from occurring.

The default max-age time is 20 seconds.

Max-age time - amount of time the switch stores BPDU information recieved on an interface.

To change the max-age timer (Global Config)

"spanning-tree vlan (#) max-age (seconds)"


Bonus Timers

-Hello Timer - how often a switch will broadcasts hellos to another switch
-Forward-delay Timer - The amount of time that listening and learning states take to enter forwarding state
-Transmit hold count - the number of BPDUs that are sent before pausing or one second.

May 5, 2010 at 3:07 PM

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