<Jeremy's IT Lab> Day 22: RSTP

RSTP

 

* Spanning Tree Versions

IEEE	Cisco
Spanning Tree Protocol (802.1D) - All VLANs share one STP instance - cannot load balance	Per-VLAN Spanning Tree Plus(PVST+) - Each VLAN has its own STP instance - can load balance
Rapid Spanning Tree Protocol (RSTP, 802.1w) - much faster than 802.1D - All VLANs share one STP instance - cannot load balance	Rapid Per-VLAN Spanning Tree Plus(Rapid PVST+) - Each VLAN has its own STP instance - can load balance
Multiple Spanning Tree Protocol (MSTP, 802.1s) - use modified RSTP mechanics - Can group multiple VLANs into diff instance (vlan 1-5 in inst 1, vlan 6-10 in inst 2) to perform load balancing	X

 

Similarities btw STP and RSTP:

- blocking specific ports prevent L2 loops

- RSTP elects RB, R, D

 

States of RSTP

- Discarding (Blocking + Disabled)

- Learning

- Forwarding

- Listening

 

Roles of RSTP

- Root port

- Designated port

- Non-designated port : 

     - Alternate: (= blocking), backup to the root port. Immediately move its best alternate port

     - Backup: (only happend via hub), discarding port receives superior BPDU from another inf

 

c.f) built in RSTP (not coved in CCNA)

- UplinkFast: RP failed, move its alternate port

- BackboneFast: Indirect failure occurs, immediately switch to forwarding state

 

** RSTP's BPDU type: 2 (classic 0)

 

Link Types of RSTP

- Edge: directly forwards w/ negotiation (= portfast)

>> spanning-tree portfast (same as classic STP)

- Point-to-point: direct connection btw two switches (full-duplex mode)

>> spanning-tree link-type point-to-point

- Shared: connection to a hub. (half-duplex mode)

>> spanning-tree link-type shared