Hi ster
Because the switch internal message forwarding processing must carry a layer of VLAN tag; Vlan 4095 is added to the packets of the main interface. When the packets are forwarded from the main interface, the VLAN 4095 will be stripped off, that is, the packets sent from the main interface are without VLAN tag. The reason why the outgoing direction message also has VLAN 4095 is that the outgoing direction near-end mirror process can be analyzed on the end if you want to verify the message before stripping the VLAN tag