LAN: LAN switching

We have discussed a variety of LAN segmentation methods (LAN technology-based LAN segmentation). Now we should carefully study the LAN switching technology. Although layer-3 switching is also used, This article focuses on the traditional layer-2 switching technology. The difference between the two is that layer-3 switching is based on the destination address forwarding group at the network layer, while layer-2 switching is based on the MAC address forwarding frame. In the past, 10Base2LAN with coaxial cables or 10BaseTLAN with one or two hubs was acceptable. Www.2cto.com does not require a lot of bandwidth for most business flows. Therefore, users can share a lot of bandwidth. However, when the network is connected to the desktop of every employee today, bandwidth becomes a very valuable resource in the face of applications such as video and audio teleconference. Before discussing the application of switches in a network, let's briefly review the history of switching technology.
In the early 1990s s, several vendors decided to develop a router replacement device because of its high production cost and difficulty in configuration. Even if earlier vswitches were cheaper than vrouters, they were actually expensive. Initially, the vswitch was limited to specific applications and used as a substitute for a more expensive vro. Compared with the complexity of vrouters, vswitches are much easier to configure. In fact, a switch is an out-of-the-box (PnP) device. In the past few years, the price of vswitches has rapidly declined. In the early days, a single port of a vswitch could easily be sold for more than $1000, but now each port of some vswitches can only sell for about $100, and its MAC address table can accommodate up to 500 items (these prices are just to show that the price of the switch has been falling for the past few years, instead of estimating the cost of building a Cisco exchange network ). The www.2cto.com switch has become so cheap that they are quickly replacing the hub location in many networks. For example, in Figure 1-2 (conflict domain and broadcast Domain Based on LAN technology) above this chapter, we have seen a LAN composed of five hubs on multiple nodes. In theory, the bandwidth of all 16 nodes can reach 10 Mbps. Imagine sending video signals to two nodes at the same time on this network. In today's network environment, the hub can be replaced by a switch, as shown in figure 1-6.

Figure 1-6 a 16-node exchange network uses a vswitch for this network. The differential segment method divides the LAN into small segments, thus increasing the effective bandwidth for each user. The differential segment method also enables each user to own his or her own lan cidr blocks, as shown in figure 1-7. As you can see, in the differential section, each site forms a conflict domain. In standard Ethernet, each user in 1-7 has its own 10 Mbps network segment. Www.2cto.com

Figure 1-7 each end user has a dedicated 10 Mbps CIDR Block switch that monitors business flows and compiles a MAC address table so that it can directly forward frames to the destination port. For example, assume that node 2 sends data to node 16. Figure 1-8 shows the data flow in the vswitch. We can see that node 8 and node 20 do not know the above data transmission, because the data is not transferred to these two ports. Www.2cto.com

Figure 1-8 data flow between node 2 and node 6 on a vswitch
Table 1-1 advantages of a vswitch over a HUB repeater: The vswitch can not only replace the hub in the LAN, but also directly access the backbone network (such as ATM and Gigabit Ethernet ), this helps to provide necessary bandwidth for applications such as real-time video or digital audio. Vswitches allow users to make full use of network bandwidth, especially in multimedia applications. Other advantages are shown in Table 1-1. Www.2cto.com