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Home > Archive > CCNP > February 2001 > BPDU creation?
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| creamy_stew 2001-02-20, 8:36 am |
| Just trying to get started on BCMSN.
Is this what happens?
1)BPDU is created by root bridge
2)For each switch the BPDU passes through, the path cost is incremented
/creamy | |
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| A BPDU is created by every bridge that's participating in Spanning Tree. Every bridge sends out its own BPDU which includes what it believes to be the root bridge and its cost to reach the root bridge.
When a bridge recieves a BPDU it does not (typically) forward it. It compares it against its current info, and if the cost to the root bridge is cheaper, then it modfies its own BPDU. Then cost to the root bridge is then incremented when the BPDU is sent out the switch's interfaces. | |
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| Creamy you are off to the right start, Spanning Tree is really complicated to explain in a short post, so I recommend Cisco's LAN Switching book. It covers more then you need to know for the Switching exam, but you won't regret reading i t and it makes a great reference.
For now suffice it to say there are two types of BPDUs and that adds to the confusion.
Yankee | |
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| Thanks for the info,
I'm just starting on the cisco BCMSN book. But when I got to the part describing the Root Port selection process, I was getting confused. I just don't understand how the bridges will know the path cost to the root.
I guess I'll have to get som additional resource. Is the LAN Switching book that CCIE prof. development one? Is it really that good as the reviews on Amazon would lead you to believe? One guy called the LAN Switching book and Routing TCP/IP _the_ two best books on networking (period)
/creamy | |
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| Yep, that's the book. I concur with the review you quoted. I have both those books and they are great references.
Yankee |
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