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ccna 200-301 network simulator tools today promo.k22Chapter 2 Network Interconnection and Reference Models*** 02Winter Similar to a bridge, a switch provides network interconnection capabilities. Each port of a switch is a separate conflict domain that can provide higher bandwidth to each workstation. Because switches can use existing cables, repeaters, hubs, and workstation NICs without having to do high-level hardware upgrades; they are transparent to workstations, which makes management overhead inexpensive and simplifies the addition, movement, and network change operations of network nodes; and they are priced comparable to hubs, so they are commonly used in today's networks. A switch can simply be thought of as a multi-port bridge, but there are still some differences between the two: first, bridges generally have only 2 ports, while switches generally have at least 4 ports, and 24-, 48-, and even more ports; second, bridges use software for forwarding, while switches use specially designed integrated circuits for hardware-based data forwarding, and switches forward data at line rate to forward information in parallel on all ports, providing much higher operational performance than traditional bridges, operating close to individual LAN performance, far exceeding the forwarding performance between ordinary bridge interconnected networks; finally, the port cost of switches is much lower than that of bridges. Depending on their function, switches can be classified as.1 Traditional Layer 2 switches, which, compared with hubs, simply have more MAC address table functionality. It belongs to the data link layer of the OSI seven-layer model, and has a broadcast domain (traditional Layer 2 switches forward broadcast or multicast frames to all ports except the receiving port), multiple conflict domains (each port is a conflict domain) O2 VLAN (VirtualLocalAreaNetwork,VirtualLocalAreaNetwork) type switch, managed switch, has more VLAN functions than the traditional type switch. It is still part of the data link layer, has multiple broadcast domains (each VLAN is a broadcast domain), multiple conflict domains (each port is a conflict domain), and can be configured with IP addresses for remote management.3 Layer 3 switches, with more routing functions than VLAN-type switches, can be imagined as a router + VLAN-type switch, but the packet forwarding performance of a Layer 3 switch is many times higher than that of a router + VLAN-type switch. It belongs to the network layer of the OSI seven-layer model, with multiple broadcast domains, multiple conflict domains. For security reasons, sometimes it is necessary to bind the IP and MAC, which requires Layer 3 and above to complete the switch, because the ordinary Layer 2 switch in the OSI seven-layer model of the second layer, can not recognize the IP address of the third layer, it can not complete the binding. For more information about switches and their configuration, refer to Chapter 9.12 of this book.2.3.3 Network Layer***The primary function of the Network layer (Network) is to accomplish the transmission of messages between hosts in the network. In a WAN, this involves generating routes from the source to the destination and selecting the optimal path based on the routing protocol used, which is covered in later chapters of this book.The network layer involves protocols such as IP, IPX, etc. Network layer devices must be able to identify the network layer addresses, such as routers and Layer 3 switches, which can do path selection based on IP addresses, and they all belong to the network layer devices.A router is a network layer device that connects multiple networks or network segments. It can "translate" data information between different networks or network segments so that they can "read" each other's data to form a larger network. It is not used for devices on the same network segment, but for devices on different segments or between different networks. The reason why a router can play a "translation" role between different networks is that it is no longer a pure hardware device, but a device that supports a rich combination of software and hardware routing protocols, such as RIP, OSPF, EIGRP, etc. These routing protocols are used to achieve the connection of different network segments or networks.