The STP protocol OSI model was developed to block Loops in layer 2. STP UplinkFast were developed that STP convergence takes much time.
Understanding Spanning Tree Uplinkfast
Nowadays networks have redundant routes and they are now indispensable. The server farm section of an enterprise network must always be active. This is because the servers need to serve their customers uninterruptedly. In addition, the UplinkFast feature is specific to Cisco only.
Therefore, in such network environments, the network redundant process is very important. The STP protocol has been developed for the network redundant process although it causes the loop in the 2nd layer devices. For example; If more than one network cable is connected to a Switch and one of these cables fails, the other must be switched on. At this point, STP comes into play.
If one of the cables connected to the switch fails, it may take some time for the other cable to enter the circuit. This cable in blocking mode can be active for up to 50 seconds. One way to shorten this period is to configure the UplinkFast on the Switch.
If you remember, we have said that in order to improve STP performance we need to configure ports-connected interfaces of devices such as computers and servers as PortFast.
How Does STP UplinkFast Work?
STP Provides a fast convergence when updating the STP protocol network map in case of a cable malfunction due to the UplinkFast feature. The UplinkFast feature was developed to work on a Switch with Blocking Mode in a backup network.
Cisco also recommends that the UplinkFast feature is implemented only at the network access layer. As a result, a Switch with UplinkFast feature will activate faster the other link when one link fails.
A Switch that has the UplinkFast feature enabled must be in Blocking mode. The reason for this is that the redundant link with UplinkFast is active quickly.
For example, in the following image, the switch to be configured as UplinkFast is specified.
As a result, when the other network cable of Switch1 in the above image fails, the UplinkFast feature will put the GigabitEthernet0/2 interface in Forwarding mode in 15-20 seconds.
How to Enable UplinkFast
To enable UplinkFast on the switch, execute the following command in Switch global config mode.
Switch# conf t
Switch(config)# spanning-tree uplinkfast
How to Enable UplinkFast on Cisco Switch ⇒ Video
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With the UplinkFast feature, we can slightly increase the Spanning Tree protocol performance over our network. In addition, you can enable BackboneFast feature on Switches. Configuring UplinkFast will be a good option when doing standard STP configuration.