Whether you are engaged in network engineering, weak current engineering, or security engineering, everyone should contact it every day – VLAN. As a basic skill, VLA is not only commonly used, but also particularly important. Today, let’s compare the VLAN applications of Cisco and Huawei.
To understand VLAN (virtual local area network), we must first understand LAN (local area network), so we must first talk about the concept of broadcast domain. What is a broadcast domain? Imagine that when the students are in class, the teacher makes a passionate speech on the platform, and all the students in the classroom can hear it. This is a broadcast domain. Similarly, in the network, by default, all hosts on the same switch can receive all information sent by all other hosts, which means that these hosts are in the same broadcast domain.
What if we want to continue to expand the scope of this broadcast domain? If we connect a cable between two switches, all the devices on the two switches are in the same broadcast domain by default, which can also be considered as the same local area network (LAN).
When it comes to VLAN, its basic function is to divide the broadcast domain. How can we narrow our broadcast domain? Why narrow the scope of broadcast domain? What are the advantages of narrowing the scope of broadcast domain? Let’s explore the following scenarios:
Scenario 1:
First, imagine that there are two different departments of the company: the Technology Department and the Finance Department. We do not want the Technology Department to communicate with the Finance Department. It would be a waste to buy two switches at this time. Then it would be easier to solve the problem with VLANs. One switch has two different VLANs. Physically, it is still a switch, but logically, it has been divided into two independent broadcast domains.
Scenario 2:
Suppose there is a very large network, and thousands of hosts are in the same broadcast domain. In this way, when each host sends a broadcast, thousands of broadcast messages will flood into the network, and there are thousands of hosts in the network. The number of broadcast messages is growing exponentially, which seriously wastes hardware resources. High end devices in the network are suffering from pressure, and low-end devices directly give up treatment and die in the same place, This is obviously an unreasonable network planning. At this time, VLAN technology can be used to limit the transmission boundary of broadcast messages to avoid situations that we do not want to see.
Having said so much, I believe you have basically understood the basic working principle of VLAN and have a preliminary understanding of VLAN. Now let’s simulate our network environment through eNSP and GNS3, and do experiments to see how specific VLANs should be configured.
First, let’s take a look at the configuration of switches by default. No matter Cisco or Huawei switches, the interfaces are in VLAN1 by default, which is why all interfaces of switches can access each other by default.
The interface mode of Huawei is the hybrid mode by default, and Cisco is the access mode by default. Huawei’s hybrid can connect users’ PCs as well as switches through multiple VLAN data and access functions; Although Cisco defaults to the access mode, Cisco’s DTP (dynamic trunk protocol) defaults to the destination mode. If the interface is used for the connection between switches in the default configuration, it will automatically negotiate to the trunk.
Configure on Huawei and Cisco switches respectively. First, enter the interface to be modified for configuration, change the interface mode to access mode, and divide the interface into corresponding VLAN.
