How to select and configure the MAC address of a vswitch

Next, we will discuss in detail about the MAC address of the vswitch, how to improve the network application capability, enrich our network practical experience, and accumulate some practical experience for future work, the following sections will conduct effective research and analysis on these issues.

If the computer in the network is connected through a hub, the network is called shared Ethernet. In a network environment connected by a hub, data collision is easy because the same data channel is used no matter whether data is sent or received.

Therefore, when sending data, the host must use the receiving line to check whether a collision has occurred. This mechanism allows the host to work only in half duplex mode. On the other hand, a hub is a physical layer device that scales up the signal through a relay.

The network connection distance and network scale are extended. The expansion of the network scale means the expansion of the collision domain, further reducing the network performance. The features of shared LAN severely restrict the improvement of network performance and are gradually replaced by the Exchange LAN consisting of switches:

(1) replacing the hub with the MAC address of the switch solves the collision problem. A switch is a device (also known as a layer-7 switch) that works on the data link layer. It can identify MAC addresses encapsulated in data frames and exchange data to specific ports based on address information.

Instead of copying the data received from one port to all other ports as the hub works. In this way, different ports of the vswitch do not have a collision, that is, the vswitch can split the collision domain. If a port is connected to only one host, the collision is eliminated.

(2) The switch solves the problem that the hub cannot fully communicate with the host connected to it. The switch uses an independent receiving and sending channel to forward data to the host connected to each interface, so that the host can work in full duplex.

(3) The switch can establish an independent data channel for any two data exchange ports to exchange data, greatly improving the efficiency of data exchange.

These features are determined by the operating principle of a vswitch. The switch determines the Data Forwarding Based on the destination MAC address encapsulated in the data frame. Before forwarding data, the switch must know the MAC address of the host connected to each of its ports and construct a MAC address table to make the correct forwarding decision.

When the MAC address of the switch receives the data frame from a port, it reads the destination MAC address information encapsulated in the data frame, and then looks at the previously created MAC address table to find the port corresponding to the destination address, data is forwarded from this interface, and other interfaces are not affected.

When the vswitch cannot find the corresponding record of the destination address and port in the address table, it forwards the data to all ports except the data source port, therefore, the broadcast data is forwarded by the switch to all its ports, so that the devices connected to the switch are in the same broadcast domain.

The following example describes how to create an address table for the MAC address of a vswitch.

In this case, host A sends A data frame (each data frame contains the source MAC address and destination MAC address) to host C. When the data frame enters the switch from Port E0, the switch checks the source MAC address field in the data frame.

Put the value of this field (the MAC address of Host A) in the MAC address table and match it with port E0, indicating that the host connected to port E0 is. The MAC address table does not contain entries about the destination MAC address (MAC address of host C). Therefore, the MAC address of the switch forwards this frame to all ports except the E0 port. This ensures that workstation C can receive the frame. The transfer process of other interfaces is the same.

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