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Spanning Tree Notes

posted 11 Apr 2016, 13:22 by DR Labs   [ updated 11 Apr 2016, 13:29 ]
***WORK IN PROGRESS***

SPANNING TREE EXAMPLE PICTURE

Original Spanning Tree  - 802. 1d
PASSIVE (convergence 50 sec + )
*Blocking - 0-26 sec
*Listening - 15 sec
*Learning - 15 sec


Rapid Spanning Tree - 802. 1w RSTP
ACTIVE  (convergence 2 sec )


Per Vlan Rapid Spanning Tree  PVSTP
ACTIVE  
1 instance per vlan (can be different topology per vlan)

Multiple Spanning Tree MSTP
ACTIVE  
cut down on spanning tree instances

Region 
Matching Name
Matching Revision No
Matching Mapping e.g. instance 0 - catch all (internal spanning tree)  instance 1 - vlan 11 to 20 instance 2 - vlan 21 to 30

*Rules

1. Root bridge election
2. Best path to the root
 2a. lowest cost
 2b. lowest ID
 3c. lowest port number (advertising switch)

*no more than 7 in the chain*

BPDU - bridge protocol data unit

every 2 seconds 
Root and Loop detection 
Multicast Address 01:80:c2:00:00:00
Bridge MAC + Bridge Priority = Bridge ID
Find best path to the root using cost


DP designated port (one per segment)

RP root port
*AP alternate port (backup to RP)
BP blocked port

Bridge Assurance -  disables ports if BPDU is NOT seen

LoopGuard - RP/AP can't become DP
RootGuard - apply on switch port to another LAN
BPDU Guard - disables ports if BPDU is seen
PortFast - disables spanning tree
BPDU filter -


MAC flap ????




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