Configuring an Access port with PortFast

Access portsAlmost 100% of Cisco switches will have a 50 second delay on a port before it goes live. What this means, is that when you plug a new device into a switch such as a PC, there will be a 50 second delay before the port will become active and the PC will be able to send and receive data. This is due to the fact the switch is running through the spanning tree process and trying to confirm that you have not just caused a loop on the network by plugging in the new device.

If you are certain that you will not be causing loops on your network by plugging certain types of devices into your switch, you can force the switch to go live immediately, rather than waiting the 50 second default value.

Firstly, the command we will use to allow this is “spanning-tree portfast”, which can only be configured on a port that is NOT acting as a trunk. So before configuring portfast we need to insure our port is configured as an access port.

When configuring a port as an access port you also want to define which VLAN (Virtual LAN) the port belongs to.

Here is the breakdown of the configuration required.

AOIP.ORG_Switch# conf t

Enter global configuration mode

AOIP.ORG_Switch(config)# interface fastethernet 0/10

Enter the interface you wish to configure

AOIP.ORG_Switch(config-if)# switchport mode access

Configure the port as an access port

AOIP.ORG_Switch(config-if)# switchport access vlan 10

Define the access port to belong to vlan 10

AOIP.ORG_Switch(config-if)# spanning-tree portfast

This configures portfast and will allow the port to go live immediately when something is plugged in without needing to wait for spanning-tree to complete.



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