Configuring access & trunk ports

To configure an interface to be an access interface, the switchport mode acess interface command is used. This type of interface can be assigned only to a single VLAN.

To configure a trunk interface, the switchport mode trunk interface command is used. This type of interface can carry traffic of multiple VLANs.

An example will help you understand the concept.

access trunk port configuration

Host A and host B are in different VLANs, VLAN 1 and VLAN 2. These ports need to be configured as access ports and assigned to their respective VLANs by using the following sequence of commands:

access ports example

Because the link between SW1 and SW2 needs to carry traffic of multiple VLANs, it needs to be configured as a trunk interface. This is done by using the following commands on both SW1 and SW2:

On SW1:

switch1 trunk example

On SW2:

switch2 trunk example

Now the link between SW1 and SW2 can carry traffic from both the VLAN1 and VLAN2. You can verify that an interface is indeed a trunk interface by using the show interface Fa0/3 switchport command on SW1:

show interface switchport

VLAN 1 doesn’t have to be created, it exists by default. Also, by default, all ports are in the VLAN 1, so Fa0/1 doesn’t need the switchport access vlan 1 command.