Switchport access/trunk mode

Two most useful modes at which ports on switch can work is ‘access’ and ‘trunk’ mode.

Access mode – all incoming traffic tagged with VLAN tag by switch and processed further. Outgoing traffic for this port processed only for associated VLAN.

Trunk mode – allows VLAN/tagged incoming traffic and sort out incoming traffic basing on tags/VLANs. Outgoing traffic for this port processed only for associated VLANs.

In general: trunk mode for inter-switch connection (or connection switch-to-servers-what support trunking), access mode – connection to end devices.

Sample configurations.

Port in access mode:

interface Ethernet1/10
  description To CoolPrinter
  switchport
  switchport access vlan 100
  no shutdown

Port in trunk mode:

interface Ethernet1/11
  description Link to AnotherCoolSwitch
  switchport
  switchport mode trunk
  switchport trunk allowed vlan 100,200-300
  no shutdown

Howto check port mode (is it in access or trunk mode):

show interface ethernet 1/54 | include Port