Deep Analysis Based on Layer 2 Exchange Technology

We hope to help you with the in-depth analysis based on the second-layer exchange technology. The second-layer network switch transmits network Frames Based on the second-layer address. The address of the second layer switch technology, also known as the MAC address of the hardware address), the second layer switch usually provides high throughput line rate), low latency about 10 microseconds), the price of each port is relatively economical.

The second layer switch technology is "Transparent" for routers and hosts, mainly complying with the 802.1d standard. This standard requires that the switch obtains the source MAC address by observing the data frame of each port. The switch establishes a MAC ing table between the MAC address and port in the internal cache. When the destination address of the data frame received by the switch is found in the ing table, the switch sends the data frame to the corresponding port.

If it cannot be found, the data frame will be broadcast to all ports of the VLAN to which the port belongs. If there is a response packet, the switch will add a new ing relationship in the ing table. When a vswitch joins the network for the first time, because the ing table is empty, all data frames are sent to all ports in the virtual LAN until the vswitch "learns" to each MAC address.

In this case, the performance of a vswitch is similar to that of a traditional shared hub at startup until the ing table is created. This method has changed the way for shared Ethernet traffic to be snatched, as if an overpass is mounted in different directions, and vehicles in different directions can access the same time, thus greatly increasing the traffic.

From the perspective of VLAN), the performance is improved because only nodes in the subnet compete for bandwidth. HOST 1 accesses host 2 and host 3 can access host 4. This advantage is even more obvious when each department has its own server.

However, this environment is changing dramatically because servers tend to be centrally managed. In addition, this mode is not suitable for Internet applications. Communication between different VLAN) needs to be completed through the router. In addition, to achieve communication between different CIDR blocks, the router also needs to be interconnected.

Vro processing capability is limited. Compared with the LAN switching speed, vro data routing speed is also relatively slow. The low efficiency and long latency of routers make it the bottleneck of the entire network. The access speed between VLAN and VLAN is the key to accelerating the entire network. In some cases, especially the Intranet), it is difficult to define the virtual LAN itself. The purpose of a layer-3 switch is to forward data packets between VLANs on the Intranet at a high rate.

VLAN Technology

In traditional LAN, channel conflicts and broadcast storms caused by channel sharing among sites are important factors affecting network performance. Generally, an IP subnet or IPX subnet belongs to a broadcast domain, so the broadcast domain in the network is divided according to the physical network. Such a network structure is lacking in terms of efficiency and security.

At the same time, because the sites on the network are bound in the physical network, and cannot be divided into logical subnets as needed, the network structure lacks flexibility. To solve this problem, the concept of virtual lan vlan is triggered. VLAN refers to the physical location where the sites in the network are not restricted, you can flexibly Add a network technology in different logical subnets as needed.

VLAN Based on Switched Ethernet

Layer-2 switching technology in switched Ethernet, VLAN technology can be used to divide a physical network connected by a switch into multiple logical subnets. That is to say, the broadcast packets sent by the sites in a VLAN will only be forwarded to the sites in the same VLAN. In the traditional LAN, due to the correspondence between the physical network and the logical subnet, the broadcast packets sent by any site will be forwarded to all sites in the network.

In switched Ethernet, sites can belong to different VLANs. Sites that make up VLANs are not limited to physical locations. They can be attached to the same vswitch or to different vswitches. VLAN technology makes the network topology flexible. For example, users on different floors or in different departments can add different VLANs as needed. So far, there are three main ways to implement VLAN Based on Switched Ethernet: Port-based VLAN, MAC address-based VLAN, and IP address-based VLAN.

Port-based VLAN

A port-based VLAN defines several ports in a vswitch as a VLAN. sites in the same VLAN have the same network address, and different VLANs need to communicate with each other through a vro. When a network site moves from one port to another, if the new port and the old port do not belong to the same VLAN, you must re-configure the network address of the site. Otherwise, the site cannot communicate over the network.

MAC address-based VLAN

Layer 2 switching technology in MAC address-based VLAN, the Switch tracks the MAC address and switch port of the site, and transfers it to a VLAN as needed when the new site accesses the network, regardless of how the site moves on the network, the MAC address remains unchanged, so you do not need to reconfigure the network address. The disadvantage of this VLAN technology is that when a site accesses the network, it is necessary to manually configure the switch to determine which VLAN the site belongs.

IP address-based VLAN

In an IP address-based VLAN, the new site does not need to perform too many configurations when accessing the network, and the switch automatically divides it into different VLANs based on the network address of each site. Among the three VLAN implementation technologies, VLAN intelligence based on IP addresses is the highest, and the implementation is also the most complex.

As a new generation of network technology, VLAN provides a good solution for the flexible configuration of network sites and network security issues. Although there are still many problems to be solved in VLAN technology, such as the unification of technical standards, the overhead of VLAN management, and the automation of VALN configurations.

However, with the continuous advancement of technology, the above layer-2 switching technology problems will be gradually solved, and VLAN technology will also be more widely used in network construction, this will play a greater role in improving network efficiency. In fact, a VLAN (Virtual LAN) is a broadcast domain.

To avoid broadcast storms caused by broadcasting on large switches, layer-2 switching technology divides the networks connected to large switches into multiple VLANs (Virtual LAN ). In a VLAN (Virtual LAN), Information sent from a workstation can only be sent to other sites with the same VLAN (Virtual LAN) number. Other VLAN (Virtual LAN) members cannot receive the information or broadcast frames.