What is Portfast in Spanning Tree Protocol?

When a computer or server is connected to the Switch port, it can access the network and communicate with other devices. Layer 2 Switches cause loops on the network, so these loops can be prevented with the STP protocol.

What is Portfast in Spanning Tree Protocol?

Understanding the Portfast Feature

Network redundancy is very important in large corporate networks. Because a high-traffic server must be constantly active on the local network or the Internet. For this reason, it is strongly recommended that you configure the Portfast feature of Cisco, as network redundancy is critical.

Sends BPDU frameworks to recalculate the STP network map when any Switch fails in a network configured with the STP protocol. It takes 50 seconds until the STP finds an alternative route. You can check the Spanning Tree port states for this case.

For example, it waits 50 seconds for a server connected to the FastEthernet 0/0 interface of the Switch to be active again when the network is disconnected. During this period, the server will not be able to provide service and this will cause a serious decline for the company. You can minimize network interruption by enabling and configuring the STP protocol on Switches that have redundant paths, as this is absolutely unacceptable in a large network.

How to Enable it?

For example, the Switch’s FastEthernet 0/0 interface must be configured as PortFast so that it is not taken into account by the Spanning Tree protocol.

The purpose of configuring this feature is to bypass the Listening and Learning steps. In short, it allows the port to enter Forwarding mode instantly. As a result, the Server connected to the FastEthernet 0/0 interface will join the network immediately without waiting for 50 seconds.

Ports configured as Portfast are ports that do not connect to Switch, Hub or Bridge devices and are used only for end-user devices.

To configure a switch port as Portfast, perform the following command on the interface.

Switch(config)# int fastEthernet 0/0
Switch(config-if-range)# spanning-tree portfast

If you want to enable Portfast on more than one port, follow the command below.

Switch(config)# int range fastEthernet 0/1 - 12
Switch(config-if-range)# spanning-tree portfast

   Video

To better understand Portfast’s logic, you can watch the video below and also subscribe to our YouTube channel to support us!

   Final Word


Since the Portfast feature is specific to Cisco branded devices, it is not used by other network devices. Thanks for following us!

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