IEEE 802.1Q

IEEE 802.1Q is an efficient #VLAN Trunking technique introduced by Institute of Electrical and Electronic Engineers (IEEE)#. It only inserts 4 bytes to the Ethernet# frame.

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VLAN Trunking

IEEE 802.1Q#
Cisco Switch Configuration

Note: If two switches can support both ISL and IEEE 802.1Q, there is a need to run switchport trunk encapsulation {trunk-protocol} (value can be dot1q or isl) before switchport mode trunk.