Switchport modes

A switch can have its ports configured as either trunk ports or access ports.

When configuring the ports of a switch in various switchport modes, the results can vary depending on what has been configured on each end of the link. The following lists the possible switchport modes that you can configure on each end and what they achieve:

  • Trunk - this mode hardwires the port to operate as a trunk
  • Access - this mode hardwires the port to operate as an access port
  • Dynamic Auto - this mode makes the port willing to convert to a trunk link
  • Dynamic Desirable - this mode makes the port actively attempt to convert the link to a trunk link

The above explanations are illustrated in the following table that depicts the result of each configuration choice on each end of a link between two switches:

TrunkAccessDynamic AutoDynamic Desirable
Dynamic AutoTrunkAccessAccessTrunk
Dynamic DesirableTrunkAccessTrunkTrunk

The above depend upon the operation of the Dynamic Trunking Protocol (DTP), which actively negotiates the automatic configuration of Trunk or Access for each port.