VLAN Trunks (3.2.2) Trunks are commonly used between switches and other network devices such as a router, another switch, or a server. A network technician must be very familiar with configuring a trunk and ensuring it works properly. Nov 28, 2016. To modify a VLAN, enter the vlan command for an existing VLAN. See the 'VLAN Default Configuration' section for a listing of the default parameters that are assigned when you create a VLAN. If you do not use the media keyword when specifying the VLAN type, the VLAN is an Ethernet VLAN. The magic of how virtual local area networks (VLANs) work is found in the Ethernet headers. When a switch receives an Ethernet frame, the frame will either already have a VLAN tag or the switch will insert a VLAN tag into the Ethernet header. If the frame was received from another switch, that switch will.