update Spanning Tree

21. Protocole Spanning Tree (part2).md

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+---
+id: 1778913634-WEMK
+aliases:
+  - Protocole Spanning Tree (part2)
+tags: []
+---
+
+# Protocole Spanning Tree (part2)
+
+## Spanning Tree Port State
+
+| STP Port State | Stable/Transitional |
+| -------------- | --------------- |
+| Blocking | Statble |
+| Listening | Transitional |
+| Learning | Transitional |
+| Forwarding | Stable |
+| Disabled |  Stable |
+
+- Root/Designated ports remain stab;e in Forwarding state.
+- Non-designated ports remain stabl in a Blocking state.
+- Listening and Learning are transitional states which are passed through when an interface is 
+activated, or when a *Blocking* port must transition to a Forwarding state due to a change in the
+network topology
+
+### Blocking state
+
+- Non designated ports are in a Blocking state
+- Interfaces in a Blocking state are effectively disabed to prevent loops.
+- Interfaces in a Blocking stae do not send/receive regular naetwork traffic.
+- Interfaces in a Blocking state receive STP BPDUs.
+- Interfaces in a Blocing state do NOT forward STP BPDUs.
+- Interfaces in a Blocking state do NOT learn [[MAC]] addresses.
+
+### Listening state
+
+- After the Blocking state interfaces with the Designated or Root role enter Listening state.
+- Only Designated or Root ports enter the Listening state (Non-designated ports are always Blocking)
+- The Listening state is 15 seconds long by default. This is determined by the *orward delay* timer.
+- An interface in the listening state ONLY forwards/receives STP BPDUs.
+- An interface in the Listening state does NOT send/receive regular traffic
+- An interface in the Listening state does NOT Learn MAC addresses from regular traffic that
+arrives on the interface
+
+### Learning state
+
+- After the Listeing state, a Designated or ROOT port will enter Learning state.
+- The Learning state is 15 seconds long by default. This is determined by the Forward delay
+timer ( the same timer is used for both the Listening and Learning states).
+- An interface in the Learning state ONLY sends/receives STP BPDUs.
+- An interface in the Learning state learns MAC addresses from regular traffic that arrives on
+the interface.
+
+### Forwarding state
+
+- Root and designated ports are in a Forwarding state.
+- A port in the Forwarding state operate as normal
+- A port in the Forwarding state sends/receives BPDUs.
+- A port in the Forwarding state sends/receives normal traffic.
+- A port in the Forwarding state learns MAC addresses.
+
+### summary
+
+
+| STP Port State |Send/Receive BPDUs | Frame forwarding | Mac address learning| Stable/Transitional |
+| -------------- |----|----|----| --------------- |
+| Blocking | No/Yes|   NO | NO  | Statble |
+| Listening | Yes/Yes|   NO | NO  | Transitional |
+| Learning | Yes/Yes|   NO | Yes  | Transitional |
+| Forwarding | Yes/Yes|   Yes | Yes  | Stable |
+| Disabled | NO/NO|   NO | NO  | Stable |
+
+
+    note: Switches do not forward the BPDUs out of their root ports and non-designated ports,
+    only their designated ports
+
+## STP timers
+
+### Hello
+
+How often the root bridge sends hello BPDUs
+duration: 2 sec
+
+### Forward delay
+
+How long the switch will stay in the Listening and Learning states (each stae is 15 seconds 
+= total 30 seconds)
+duration: 15sec
+
+### Max Age
+
+How long an interface will wait after ceasing to receive Hello BDPUs to change the STP topology
+duration: 20 sec (10*hello)
+
+- If another BPDU i received before the max age timer counts down to 0, the time will reset to 20 
+seconds and no changes will ocur.
+
+- If another BPDU is not received the max age timer counts down to 0 and the switch will
+reevaluate its STP choices, including root bridge, and local root, designated, and non-designated ports
+
+- if a non-designated port is selected to become a designated or root port, it will transition 
+from the blocking state to the listening state (15 seconds), learning state (15 seconds),
+and then finally the forwarding state. So it can take a total of 50 seconds for a blocking
+interface to transition to forwarding
+
+## Review
+
+- STP state/timers
+- STP BPDU
+- STP optional features
+- STP configuration