Understanding VLAN Trunking

Zyxel_Adam Posts: 364  Zyxel Employee
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VLAN Trunking, conforming to the 802.1q standard, allows a switch to handle and pass through frames from VLANs that are not configured on it. Normally, a switch discards frames from unknown VLANs, but VLAN Trunking overcomes this limitation, enabling easier configuration and better network flexibility.

Setting Up VLAN Trunking

To implement VLAN Trunking, activate it on a specific port. This action permits the passage of frames from VLANs that the switch does not recognize. It's particularly beneficial when you want to establish VLANs on endpoint devices without needing to replicate these VLAN configurations on every intermediate device in the network.

For instance, consider you need to set up VLAN 20 and VLAN 30 on Switch A and Switch B. In the absence of VLAN Trunking, you would be required to configure VLAN 20 and VLAN 30 on all intermediate switches (Switches C, D, and E) as well. If not, these switches would drop frames tagged with unknown VLAN groups. However, with VLAN Trunking activated on the relevant ports of the intermediate switches, there is no need to configure VLAN 20 and 30 on these switches. Switches C, D, and E will then automatically allow the passage of frames tagged with VLAN 20 and 30 through their trunking ports, even though these VLAN groups are not configured on them.

How to configure:

Web GUI of v4.70

Advanced Application > VLAN > VLAN Configuration > VLAN Port Setup

Web GUI of v4.80


*You can use VLAN-trunking as Trunk allowed VLAN all.

VLAN trunking setup for GS1900 series