When a trunk port sends packets, the VLANID is the same as the PVID, why should the VLAN information

If the trunk port receives the VLAN data marked with this trunk port from the uplink port, the VLAN information of this data will be stripped and then transferred to other downlink ports.

When the trunk port receives the data with the same PVID from the downlink port, it will add the VLAN information of the trunk port to the data, and then connect the data to the uplink port**.

If you don't strip it, don't you go out?

I don't know if you have noticed: When receiving packets, ACCESS, TRUNK, and HYBRID first determine whether there is VLAN information, if not, then put the pvid of the port and exchange it**, if there is, ACCESS is directly discarded (default), trunk and hybrid are to determine whether the port allows the VLAN data to enter, if it can, then **, if not, it is discarded, so, The conclusion is that if they receive packets without VLAN information, they are directly received, so for convenience, if the VLAN information can be removed when sending packets, they can directly remove (strip), and after stripping, they will directly discard (because this VLAN information has no effect), and the packets will be directly sent to the port that matches the VLAN information, and exchanged**. 。

It was only then that I found out that the problem was in 2012.

Summary. Hello dear, if the PVID of the switch interface at both ends of the trunk link is 100, the data frame of VLAN100 is 200 on the trunk link. Data Transfer Process:

The PC sends a normal data frame packet to the switch, and after entering the switch port, the data frame will be tagged with a VLAN by the port and then enter the switch to compare the VLAN, if it is found that there is no VLAN inside, then the data frame will be discarded, and if there is such a VLAN, it will be transmitted according to the comparison table in the VLAN.

If the PVID of the switch interface at both ends of the trunk link is 100, the data frame of VLAN100 is the data frame on the trunk link.

Hello dear, if the PVID of the switch interface at both ends of the trunk link is 100, the data frame of VLAN100 is 200 on the trunk link. Data transmission process: the PC sends normal data frame packets to the switch, and after entering the switch port, the number of destroyed spring sheds will be marked with a VLAN tag by the port, and then enter the switch internal comparison VLAN, if it is found that there is no VLAN inside, then the data frame will be discarded, and if there is this VLAN, it will be transmitted according to the comparison table in the VLAN.

The advantages of VLAN's brotherhood: 1. Isolate the broadcast domain: The switch itself is a broadcast domain in the early stage, and the VLAN can isolate the broadcast domain through the VLANID to suppress the impact of the broadcast storm, and will only flood in the VLANID.

2. Improve the security of the LAN: If a VLAN network segment is attacked, it will not affect the work of other VLANs. 3. Easy to manage

VLANs can be assigned based on departments to facilitate network management.