attributes to reduce STP Corvengence time

UplinkFast, BackboneFast and Portfast are Cisco’s proprietary extensions to the Classic Spanning Tree Protocol (STP 802.1 D) algorithm. The purpose UplinkFast, Backbone Fast and Portfast are to reduce the time it takes for classic Spanning Tree Protocol (STP) to converge after a link failure.

 We were talking about Rapid Spanning Tree Protocol, and how it could it decrease the conversion time but in case we don't  have Rapid Spanning Tree protocol this features can help.

 Uplinkfast

UplinkFast  is useful for Direct Link failures (a link connected directly to the same Switch). The UplinkFast extension can dramatically decrease the convergence time of the Spanning Tree Protocol (STP) in the event of the Direct link  failure of an uplink on an Access Layer switch.

It will allow a transition from a blocking port to forwarding almost inmedialtelly and educate the topology about how to get to that mac address.

  Rapid STP  protocol have a feature similar to this so we don't need it there

The UplinkFast feature is designed to run in switches that has at least one alternate/backup port which is in the blocking state.

•  Uplinkfast is connected on Access layers switches to quickly reconverge ( no distributed or Core switches)
• It's globally enable on switches (no port configured)
• React to a direct link failure

When a switch loses connectivity, alternate paths are used for communication. By enabling UplinkFast we can speed-up the selection of a new Root Port when a link or switch fails  or when the Spanning Tree Protocol (STP) reconfiguration happens (50 seconds to converge).

When UplinkFast is enabled, Root Port transitions to the Forwarding State immediately without going through the Listening State and Learning State, as in normal Spanning Tree Protocol (STP) Operation.
UplinkFast provides the immediate shift to alternate port by determining the possible paths going to the Root Switch (Root Bridge).

The collection of possible paths going to the Root Switch (Root Bridge) are called uplink group. In a switch, the uplink group consists in the Root Port and all the ports that provide an alternate connection to the Root Switch (Root Bridge).

You can not use uplink when you are using rapid pvst+  :

We will delete the previous vlan configuration

 

We could see that Uplinkfast was successfully enable!

Backbonefast

Allow a switch to initiate reconvergence in the even of a indirect link failure.Like uplinkfast doesn't needed using rapid pvst because it has a similar feature build-in .

1. Normally configured on all network switches
2. React to an indirect link failure
3. Globally enable on a switch
           

 The Backbone Fast feature provides fast failover when an indirect link failure occurs. Failover occurs when the switch receives an inferior BPDU from its designated bridge. An inferior BPDU indicates that the designated bridge has lost its connection to the Root Bridge.

The Backbone Fast feature includes a mechanism that allows for an immediate check to see if the BPDU information stored on a port is still valid if an inferior BPDU is received. This is implemented with a new PDU and the Root Link Query, which is referred to as the RLQ .
Upon receipt of an inferior BPDU, the switch will send out an RLQ  on all Non-Designated Ports, except for the port on which the inferior BPDU was received. If the switch is either the Root Bridge or has lost its connection to the Root Bridge, it will respond to the RLQ

 Let’s check  our  topology.
 SWITCH A is the root, and the link between SWITCH A and SWITCH B fails.

1. SWITCH C receives a BPDU from SWITCH B advertising itself as the root bridge. 
2. Since SWITCH C knows that the correct root bridge, SWITCH A is still alive and well, SWITCH C is able to inform SWITCH B that it’s not the root, and that the root bridge is now accessible to SWITCH B through SWITCH C, instead of a direct connection.

 

We see over here how backbonefast was enable!

Portfast

 The time Spanning Tree Protocol (STP) takes to transition ports over to the Forwarding state can cause problems. PortFast is a Cisco network function which can be configured to resolve this problem.

1.  Configure on port using end point 
2. Can be enable globally or on a port to port basics (for non-trunking ports)
3. Allows a switch port to active almost immediately when an end station is attached to the port

 This factor of time is not an issue for many people, but it can cause problems for some. For example, if you power up my computer in the morning ( an end point), power goes to the network card immediately, and the port on the switch enters the Listening state.
 PortFast is the solution to this problem of delays when client computers are connecting to switches. PortFast is not enabled by default. With PortFast enabled on a port, you  tell spanning tree not to implement STP on that port.

We learned how to do uplinkfast, backbonefast and portfast. The lesson and lab were  successful!