Q: 

A,B 2 switches between the network cable connection port Ethernet 0/0/1 are set to trunk vlan2, A switch under the Ethernet0/0/2 port is set to access, pvid=2, connected to PC A. 

B switch under the Ethernet0/0/2 port is set to access, pvid=2, connected to PC B. PC A ping PC B, mirroring capture Ethernet 0/0/1 port, pvid=2, connected to PC B.

Switch B's Ethernet0/0/2 port is set to access, pvid=2, connecting to PC B. PC A pings PC B, and PC A's port is set to access, pvid=2.

PC A ping PC B ,mirror capture packet on port Ethernet 0/0/1, how come there is no Vlan tag? Physical actual packet capture, packets do not have vlan label? eNSP simulation has it.

A: 

What does trunk vlan 2 mean? If it is a trunk port, allow vlan 2, and the pivd is set to vlan 2, then the vlan 2 data frame is stripped of the vlan 2 label when it goes out through that trunk port, so you capture the packet at the trunk port and find that it is not labeled with a vlan label.

And when that data frame enters on the opposite end trunk port, because it does not carry a vlan label, it is tagged with the same label as the trunk port's pvid, i.e., the vlan 2 label. It is then sent out the vlan 2 access port, so the two ends are able to communicate, but the route trunk port is indeed untagged because it is stripped.

You can leave the trunk port's pvid as default (pvid vlan 1) or you can change it to another vlan, in any case as long as the trunk port's pvid is not vlan 2, then vlan 2 data frames are carrying labels when they are routed to the trunk port.