Rapid Spanning Tree (RSTP)

Done

Speed	STP Cost	RSTP Cost
10 Mbps	100	2,000,000
100 Mbps	19	200,000
1000 Mbps	4	20,000
10G	2	2,000
100G	X	200
1 Tbps	X	20

Root Ports stay the same

Designated Ports, stay the same, being the one who sends the “Best” BPDUs

Non-Designated is renamed to Discarding, and is split into:
- Alternate Port
  - Functions the same as the blocking port, and the same rules apply.
- Backup Port
  - It appears when a switch has ports in the same collision domain, due to a hub. With the one with the lowest ID being the designated and the other ones the backup, ready to forward in case the designated one fails

UplinkFast is built-in to RSTP that moves an Alternate Port immediately from discarding into forwarding

BackboneFast allows its previously discarding port to move directly to forwarding state when it starts receiving Hello BPDUs from a inferior root bridge candidate, meaning it has lost its previous root port and now it thinks it is a root bridge. So the switch with the discarding port expires the age timers of its interface and moves directly to forwarding state, forwarding the superior BPDUs to the switch that lost the root port (inferior root bridge candidate). This function is also built-in RSTP.

💡

IMPORTANT: In the classical STP, only the Root Bridge originates BPDUs, while in RSTP all switches send BPDUs from their designated ports.

Classical STP waits 20 seconds (10 Hello times) in order to consider an interface lost, while Rapid STP only waits 6 seconds (3 BPDUs). It will then flush the all the MAC addresses associated with that interface, so a new path can be learned.

Link Types

Edge
1. Connected to the end hosts, it functions the same as a PortFast enabled interface

Point-to-Point
1. Connects switches directly
1. Full-Duplex

Shared
1. Connects switches via Hub
1. Half-Duplex

configure terminal
interface g0/1
spanning-tree link-tryp {point-to-point/shared}

configure terminal
interface g0/1
spanning-tree portfast