Technical analysis: VLAN access Link

Vswitch Port
Vswitch ports can be divided into the following two types:
Access Link)
Aggregation Link Trunk Link)
Next, let's learn the characteristics of these two different ports in sequence. First, we will learn "Access Links ".
Access Link
The access link refers to the port "only belongs to one VLAN and forwards data frames to this VLAN. In most cases, the access link is connected to a client.
Generally, the order of VLAN settings is as follows:
Generate VLAN
Set the access link to determine which VLAN each port belongs)
The method for setting access links can be fixed in advance or dynamically changed based on the connected computer. The former is called "static VLAN", and the latter is naturally "dynamic VLAN.
Static VLAN
Static VLAN is also known as a port-Based VLANPort-Based VLAN ). As the name suggests, it is to specify the VLAN for each port.

Because you need to specify ports one by one, when the number of computers in the network exceeds a certain number, for example, hundreds of computers), the configuration operations will become very complicated. In addition, each time the client changes the connected port, it must change the VLAN settings of the port at the same time-this is obviously not suitable for networks that need to change the Extension Structure frequently.

Dynamic VLAN
On the other hand, a dynamic VLAN is used to change the VLAN of a port at any time based on the computer connected to each port. This avoids the above changes and settings. Dynamic VLANs can be roughly divided into three categories:
VLANMAC Based VLAN Based on MAC addresses)
Subnet-Based VLANSubnet Based VLAN)
User-Based VLANUser-Based VLAN)
The difference lies in determining the VLAN to which the port belongs based on the information of the OSI reference model.
A VLAN based on a MAC address is used to query and record the MAC address of the NIC on the computer connected to the port to determine the port. Assume that a mac address "A" is set to VLAN "10" by the switch, no matter which port the computer with the MAC address "A" is connected, all ports are allocated to VLAN10. When the computer is connected to Port 1, Port 1 belongs to VLAN10, while Port 2 belongs to VLAN10.

Because the VLAN is determined based on the MAC address, it can be understood that this is a way to set the access link on the second layer of OSI.
However, when configuring a VLAN based on a MAC address, you must investigate the MAC address of all connected computers and log on to it. If the computer switches the NIC, you still need to change the settings.
The subnet-based VLAN is determined by the IP address of the connected computer. Unlike the MAC address-based VLAN, even if the computer changes the MAC address due to NIC switching or other reasons, as long as its IP address remains unchanged, it can still add the previously set VLAN.

Therefore, compared with VLAN Based on MAC addresses, it is easier to change the network structure. The IP address is the layer-3 Information in the OSI reference model. Therefore, we can understand that subnet-based VLAN is a method for setting access links on the layer-3 of OSI.
Based on the user's VLAN, the user currently logged on to the computer connected to each port of the switch determines which VLAN the port belongs. The user identification information here is generally the user logging on to the computer operating system, for example, the user name used in the Windows domain. These usernames are information above the OSI layer.
In general, the higher the OSI layer, the more suitable it is to build a flexible network.
Summary of Access Links

In summary, there are two methods to set the access link: static VLAN and dynamic VLAN. Dynamic VLAN can be further subdivided into several small categories.
Among them, subnet-based VLANs and user-based VLANs may be implemented by network device vendors using unique protocols, and the interconnection between devices of different vendors may lead to compatibility issues; therefore, when selecting a vswitch, be sure to confirm in advance.
The following table summarizes information about static and dynamic VLANs.

Type		Explanation
StaticVLAN: Port-based VLAN)		Assign the ports of the vswitchVLAN
DynamicVLAN	Based onMAC address VLAN	According toMAC Address Settings
	Subnet-basedVLAN	According toIP Address Settings
	User-basedVLAN	Set the port based on the logon user settings on the computer connected to the port