A normal (untagged) broadcast packet is sent into a trunk port on a switch, the vlans it accepts are 11, 12, and 13. What will happen to that packet? Will it be sent out all access ports with vlan 11 12 and 13? Will the packet be dropped? Will it only be sent out another trunk port? Or, will something I haven't considered happen?


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2 Answers 2


It will be sent out all ports on the native (untagged) VLAN. If there is no native VLAN, the packet is dropped.


By default the native VLAN is enable on each trunk port of the switch. In this case your packet will not be dropped, but will be tagged with the same number of VLAN that native VLAN is.

For a clarification, what native vlan does:

  • Tags incoming un-tagged traffic on trunk links with the native VLAN.
  • Un-tag outgoing traffic that has already been tagged with same VLAN that is being used for the native VLAN on the trunk.

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