ajout Etherchannel

22 Rapid Spanning Tree Protocol.md

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+---
+id: 22 Rapid Spanning Tree Protocol
+aliases: []
+tags:
+  - CCNA
+---
+
+# Rapid Spanning Tree Protocol 
+
+## Spanning Tree Version
+
+### Industry standards (IEEE)
+
+Spanning Tree Protocol (802.1D) 
+- The original STP
+- ALl VLANs share one STP instance.
+- Therefore, cannot load balance.
+
+Rapid spanning Tree Protocol (802.1w)
+- Much faster at converging/adaptating to network changes than 802.1D
+- All VLANs share one STP instance.
+- Therefore, cannot load balance
+
+Multiple Spanning Tree Protocol (802.1s)
+- Uses modified RSTP mechanics.
+- Can group multiple VLANs into different instacnces (ie. VLANs 1-5 instance 1, VLANs 6-10 in instance
+2 ) to perform load balancing
+
+### CISCO Versions
+
+Per-VLAN Spanning Tree Plus (PVST+)
+- Cisco's upgrade to 802.1D
+- Each VLAN has its own STP instance.
+- Can load balance by blocking different ports in each VLAN.
+
+Rapid Per-VLAN Spanning Tree Plus (Rapid PVST+)
+- Cisco's upgrade to 802.1w
+- Each VLAN has its own STP instance
+- Can load balance by blocking different ports in each VLAN
+
+## Rapid spanning Tree Protocol
+
+Cisco's summary:
+"RSTP is not a timer-based spanning tree algorithm like 802.1D. therefore, RSTP offers an improvement 
+over the 30 seconds or more that 902.1d takes to move a link to forwarding. the heart of
+the protocol is new bridge-bridge handshake mechanism, which allows ports to move directly to forwarding."
+
+### Similarities between STP and RSTP:
+
+RSTP serves the same purpoe as STP, blocking specific ports to prevent Layer2 loops.
+- RSTP elect a root bridge with same rules as STP
+- RSTP elects root ports with the same rules as STP.
+- RSTP elects designated ports with the same rules as STP
+
+### Differences
+
+#### COST
+
+| speed | STP COST | STP COST |
+| -------------- | --------------- | --------------- |
+| 10 Mbps | 100 | 2,000,000 |
+| 100 Mbps | 19 | 200,000 |
+| 1 Gbps | 4 | 20,000 |
+| 10 Gbps | 2 | 2,000 |
+| 100 Gbps | x | 200 |
+| 1 Tbps | x | 20 |
+
+
+#### Port State
+
+| STP Port State | Send/Receive BPDUs | Frame Forwarding | MAC Learning | Stable/Transitional |
+| ------------- | -------------- |  -------------- | -------------- | -------------- |
+| Discarding | NO/YES | NO | NO | Stable | 
+| Learing | YES/YES | NO | YES | Tranisitional | 
+| Forwarding | YES/YES | YES | YES | Stable | 
+
+
+- if a port is administratively disabled (shutdown command) = discarding state
+- if a port is enabled but blocking traffic to prevent Layer 2 loops = discarding state
+
+#### Port Roles
+
+*The root port role remains unchanged in RSTP.*
+- The port wthat is closet to the root bridge becomes the root port for the switch.
+- The root bridge is the only switch that doesn't have a root port.
+
+*The designated port role remains unchanged in RSTP.*
+- The port on a segment (collision domain) that sends the best BPDU is that 
+segment's designated port (only one per segment)
+
+- *The non designated port role is split into two separate roles in RSTP*:
+  - The alternate port role 
+  - the backup port role
+
+##### Alternate port Role
+
+The RSTP alternate port role is discarding port that receives a superior BPDU from another switch.
+- This is the same as what you've learned about *blocking*  ports in classic STP.
+- Functions as a backup to the root port.
+- If the root port fails, the switch can immediately move its best alternate port to forwarding
+
+      This immediate move to fowarding state functions like a classic STP optional feature called 
+      UplinkFast. Because it is built into RSTP, you do not need to activate UplinkFast when using 
+      RSTP/Rapid PVST+
+
+      One more STP optional feature that was built into RSTP is BackboneFast.
+      Backbone Fast allows SW3 to expire the made age timers on its interface and rapidly forward the superior
+      BPDUs to SW2.
+      This functionality is built into RSTP, so it does not need to be configured
+
+##### Backup port role
+
+The RSTP backup port role is a discarding port that receives a superior BPDU from another 
+interface on the same switch.
+- This only happnes when two interfaces are connected to the same collision domain (via a hub)
+- Hubs are not used in modern networks, so you will probably not encounter an RSTP backup port.
+- Function as backup for a designated port
+- The interface with the lowest port ID will be selected as the designated port and the other will be the
+backup port
+
+### BPDU
+
+In classic [[STP]], only the root bridge originated BPDUs, and other switches just forwarded the BPDUs
+they received.
+In Rapid STP, all Switches originate and send their own BPDUs from their designated ports
+
+All switches running Rapid STP send their own BPDUs every hello time (2 seconds).
+- Switches 'age' the BPDU information much more quickly, in classic STP a switch waits 10 hello intervales
+(20 seconds). In rapid STP, a switch considers a neighbor lost if it misses 3 BPDUs (6 seconds)
+It will the 'Flush' All MAV addresses learned on that interface
+
+## RSTP Link Types
+
+RSTP distiguishes between three different 'link types'
+- Edge: a port that is connected to an end host. Moves directly to forwarding without negotiation.
+- Point-to-point: a direct connection between two switches
+- Shared a connection to a [[hub]]. Must operate in half-duplex mode.
+
+### Edge
+
+Edge ports are connected to end hosts.
+- Because ther is no risk of creating a loop, they can move stright to the forwarding state without the 
+negotiation process.
+- They function like a classic STP port with PortFast enabled
+
+```Cisco
+SW1(config-if)# spanning-tree portfast
+```
+
+### Point-to-Point
+
+Point-to-point ports connect directly to another switch
+- They function in full-duplex
+- you don't need to configure the interface as point-to-point (it should be detected)
+
+```Cisco
+SW1(config-if)# spanning-tree link-type point-to-point
+```
+
+
+### Shared
+
+shared Ports connect to another switch (or switches) via a hub.
+- They function in half-duplex
+- You don't need to configure the interface as shared (it should be detected)
+
+```Cisco
+SW1(config-if)# spanning-tree link-type shared
+```
+
+### Configuration
+
+
+```Cisco
+SW3(config)# spanning-tree mode rapid-pvst
+
+SW3(config)# do show spanning-tree
+```
+
+
+## Review
+
+Comparison of [[STP]] versions (standard vs [[Cisco]])
+
+Rapid PVST+