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--- icnd2:spanning-tree [2024/04/28 03:10]
114.119.158.167 old revision restored (2023/10/12 11:33)
+++ icnd2:spanning-tree [2024/10/31 21:17] (current)
114.119.145.216 old revision restored (2018/01/13 10:55)
@@ Line 1: / Line 1: @@
 =====WHY=====
-Frame Loop Prevention Mechanism. Achieved by blocking all but one **''ROOT''** port to a **''ROOT''** switch. Redundant links are then blocked to create a loop-free environment.
+Frame Loop Prevention Mechanism. Achieved by blocking all but one ROOT port to a ROOT switch. Redundant links are then blocked to create a loop-free environment.
 =====CONCEPT=====
-  * It does this with Each Switch broadcasting a **''HELLO BPDU''**, made up of that SW's **''Priority + MAC''**. Default Priority is 32768. The SW with the **''lowest BPDU''** (superior) is elected the ROOT BRIDGE.
+  * It does this with Each Switch broadcasting a BPDU, made up of that SW's Priority + MAC. Default Priority is 32768. The SW with the lowest BPDU (superior) is elected the ROOT BRIDGE.
-  * Each SW will then determine a **''ROOT PORT''**, one per SW. A **''DESIGNATED''** port is then elected on each segment.
+  * Each SW will then determine a ROOT PORT, one per SW. A DESIGNATED port is then elected on each segment. There can only be one DESIGNATED port per SEGMENT/LINK.
-  * There can only be **one DESIGNATED port per SEGMENT/LINK. **
+  * Any port that is not DESIGNATED or a ROOT port, is then set to a BLOCKING state.
-  * Any port that is **not** **''DESIGNATED''** or a **''ROOT''** port, is then set to a **''BLOCKING''** state.
-Note that once a ROOT Bridge is elected, all other bridges will only forward HELLO BPDU's **originating** from the **''ROOT BRIDGE''**. The Root cost is incremented as the **''HELLO BPDU''** is **received (COST=$COST+$PORT_COST)**. The Root Cost **starts off @ 0** from the **''ROOT''**. Each subsequent Bridge tacks on it's **COST TO THE ROOT BRIDGE** as it is **received**.
 ==TO DETERMINE A DESIGNATED PORT:==
@@ Line 13: / Line 11: @@
   * --COST IS SAME: Is my my Bridge ID lower?
   * --if NO to either, PORT WILL BE BLOCKED!
-==PORT COSTS==
-  * **10Mb link:** **''100''**
-  * **100Mb link:** **''19''**
-  * **1Gb Link:** **''4''**
-=====Root Port Election=====
-SW1 <> SW2 (Fa0/11-> Fa0/11, Fa0/12 -> Fa0/12)
-The BPDU with the lowest **''Root Port Cost (RPC)''** will be elected the **''Root Port''**. Considering the above topology, both ports being received on FastEthernet ports will have a cost of 19 added to the RPC once it hits SW2. The RPC will match on both interfaces. A tie-breaker is required to further determine the Root Port.
-The **''port''** that recieves the **''lowest BPDU''** is **''elected''** the root port. Considering the above topology, SW2 will receive the same BPDU from SW1 on BOTH PORTS. With the BPDU the same, it ties. A tie-breakier is needed to determine the **''ROOT PORT''**.
-====Tie Breakers====
-stuff
 =====COMMANDS:=====

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