Example flows for tagged and untagged packets.
An untagged packet arriving at Port3 is assigned VLAN 100 (the native VLAN) and flows to all egress ports that will send VLAN 100 (Port1 and Port4).
A tagged packet (VLAN 100) arriving at Port4 is allowed (VLAN 100 is allowed). The packet is sent out from Port1 and Port3. On Port3, VLAN 100 is the native VLAN, so the packet is sent without a VLAN tag.
An untagged packet arriving at Port 4 is assigned VLAN 300 (the native VLAN). Then it flows out all ports that will send Vlan300 (Port 3).
A tagged packet (VLAN 300) arriving at Port3 is allowed. The packet is sent to egress from Port4. VLAN 300 is the native VLAN on Port4, so the packet is sent without a VLAN tag.