Is the VLAN generally set to tag or untag?

Untag is generally used for vlan. Tag is used by multiple vlans. If vlan is compared to an isolation steel plate, then tag is an armor-piercing bullet, and untag is an egg because it has no penetrating ability.

1, the port receives data When:

(1) If the port is in tagged mode, when the data packet itself does not contain VLAN, the input data packet will be added with the default vlan.

(2) If the data packet itself already contains VLAN, then it will not be added.

(3) If it is untagged mode, all input data packets must be added with the default vlan. It does not matter whether the incoming packet has a VLAN tag or not.

2. When the port sends data:

(1) If the port is in tagged mode, and if the default VLAN of the port is equal to the VLAN contained in the sent data packet, then the VLAN tag will be changed from Removed from the sent data packet; if not equal, the data packet will be sent out with the VLAN to achieve transparent transmission of the VLAN.

(2) If it is untagged mode, no matter what the default VLAN of the port is and whether it is equal to the VLAN of the data packet to be output, the VLAN ID will be removed from the data packet.

Extended information:

1, advantages and disadvantages of static VLAN

(1) It can be said that static VLAN There is a slight similarity with port-based VLAN, users can allow one or more switch ports on the switch to form a slightly larger virtual LAN. In a certain sense, static virtual LAN makes up for the shortcomings of port-based virtual LAN to some extent.

(2) In terms of shortcomings, although static VLAN can set multiple ports into a virtual LAN, because the inconsistency between the ports and the virtual LAN will often directly cause the personnel in a certain virtual LAN to be unable to function normally. To access the VLAN where he was originally located, the network administrator needs to cooperate at any time to modify the port on the line in a timely manner.

2, Advantages and Disadvantages of Dynamic VLAN

(1) First of all, it is suitable for current wireless LAN technology. Secondly, when users need to move the working base point, they don’t have to worry about static VLAN. Some problems with virtual LANs and port-based virtual LANs occur in dynamic virtual LANs, because in the early stages of establishment of a dynamic virtual LAN, the network administrator has input all MAC addresses in the entire network into the router.

(2) At the same time, how to use the router to automatically distinguish which virtual LAN each computer belongs to through the MAC address, and then connect this computer to the corresponding virtual LAN. Speaking of shortcomings, the shortcomings of dynamic virtual LAN are not really shortcomings. It is just that in the early days of VLAN establishment, network managers need to register the MACs of all machines and then divide the different permissions of the machines corresponding to the MACs.

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