TRENDnet TEG-S4000I - Manual (Page 69)

Continue to press button and the next page VLAN 3 appears
Click the checkbox on Port 1, Module 1.
Remember to click “ Apply “ button after you finish your setting.
Now, you have finished one Tagging VLAN setting.
While you connect this Switch to another Modular Switch to form
tagging VLAN, remember that the other Modular Switch should have
the same Tagging VLAN setting.
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