In VLAN Trunking, a tag will assign to the frame to indicate their #Virtual LAN (VLAN) belonging which is handled by either a switch or a router. After the frame passed through a trunk link, the tag will be removed from the packet when it reaches the destination node or non-trunk link, usually a switch.
It is advised to have access ports when only a single port is connected to the port, multiple devices that belongs to the same VLAN are connected to the port, or the link only carry a single VLAN when there is another switch connected to the interface. Trunk ports should be used when there is a need to carry multiple VLANs.
There are currently two standards for VLAN Trunking:
- Inter-Switch Link (ISL), Cisco legacy proprietary method
- IEEE 802.1Q#
Note: These two standards are incompatible to each other. If two Switch# support different standard and only that standard, then it is not possible to establish a trunk link between them.