Switches, routers, hubs, and NICs

Hub
A hub is actually a multi-port repeater. Hubs generally have 4, 8, 16, 24, 32, and other RJ45 interfaces. Through these interfaces, the hub can then complete the "relay" function for the corresponding number of computers (sort out the signals that are not completely degraded, generate a complete signal again, and then continue to transmit ). Because it is in a "center" position in the network, the hub is also called "Hub ".
The working principle of a hub is very simple. For example, a hub with eight ports is connected to eight computers. The Hub is in the "center" of the network and forwards signals through the hub. Eight computers can communicate with each other. The specific communication process is as follows: if Computer 1 needs to send a piece of information to computer 8, when computer 1's Nic sends the information to the hub through twisted pair wires, the Hub does not directly send the information to computer 8. It broadcasts the information and sends the information to the eight ports at the same time, when the computer on the eight ports receives the broadcast information, it checks the information. if it finds that the information is sent to itself, it receives the information; otherwise, it ignores it. Because the information is sent from computer 1 to computer 8, computer 8 will eventually receive the information, this information is not received because it is not its own.

Vswitch
A switch is also called a switch-type hub. It re-generates information and forwards it to a specified port after internal processing. It can automatically address and exchange information, the switch sends each information packet independently from the source port to the destination port based on the destination address of the information packet to avoid collision with other ports. A vswitch in the broad sense is a device that implements information exchange in a communication system.
In a computer network system, switches are designed to address the weakness of the shared working mode. A hub is represented by a shared working mode. If a hub is compared to a postman, the postman is an unliterate "dumb"-asking him to send a mail, he doesn't know how to send the mail to the recipient directly based on the address on the letter. Instead, he only delivers the mail to all the recipients, and then asks the recipient to determine whether the recipient is his own Based on the address information! The switch is a "smart" postman-the switch has a high-bandwidth back bus and an internal switching matrix. All the ports of the switch are attached to the back bus. When the control circuit receives the data packet, the processing port searches for the address table in the memory to determine the target MAC address (the hardware address of the NIC) the port on which the NIC is attached, and data packets are quickly transmitted to the destination port through the internal switching matrix. If the target Mac does not exist, the switch broadcasts all the ports. After receiving the port response, the switch "learns" the new address and adds it to the internal address table.
It can be seen that when receiving a "letter" from a network card, the switch will quickly send the letter to the recipient based on the above address information and its "resident residence booklet. In case the recipient's address is not in the "user register", the switch will distribute the email to all people like a hub, and then find the recipient. After finding the receiver, the switch will immediately register the information of the receiver to the "user register", so that the mail can be delivered quickly when serving the customer.

Vro
A vro is a key device connecting networks. As a hub connecting different networks, the router system forms the main context of the TCP/IP-based Internet.
The reason why a router is at a critical position in the interconnect network is that it is at the network layer. On the one hand, it can span different physical network types (DDN, FDDI, Ethernet, etc ), logically, the entire interconnected network is divided into logically independent network units, so that the network has a certain logical structure. The main task of a router is to find an optimal transmission path for each data frame passing through the router and transmit the data to the destination site effectively.
The basic function of a vro is to transmit data (IP packets) to the correct network. The segments include: 1. IP datagram forwarding, including datagram path finding and transmission; 2. subnet isolation to prevent broadcast storms. 3. Maintain route tables and exchange route information with other routers. This is the basis for IP packet forwarding; 4. IP datagram error handling and simple congestion control; 5. Filtering and accounting of IP datagram.
A vro forms the backbone of the Internet. The processing speed is one of the major bottlenecks of network communication. Its Reliability directly affects the quality of network interconnection. Therefore, vro technology remains at the core of Internet research.
Recently, many people are asking what the vswitch, hub, and router are, what are their functions, and what are their differences. I will give some simple answers to these questions.

First, the hub, that is, the hub. Its function can be simply understood as connecting some machines to form a LAN. The switch (also known as the switch-type hub) works basically the same as the hub. However, there is a difference between the two in terms of performance: the hub uses the shared bandwidth method, while the switch is the exclusive bandwidth. In this way, when there are many machines or a large amount of data, the two will be obvious. A vro differs significantly from the preceding two. Its function is to connect different CIDR blocks and find the most suitable path for data transmission in the network. In general, individual users have little need. A vro is generated after a vswitch, just as a vswitch is generated after a hub. Therefore, the vro and vswitch are also associated, and they are not completely independent of each other. Vro mainly overcomes the problem that vswitches cannot route and forward data packets.

In general, the main difference between a vro and a vswitch lies in the following aspects:

(1) different levels of work

The original switch was working on the data link layer of the OSI/RM open architecture, that is, the second layer. At the beginning, the router was designed to work on the network layer of the OSI model. Because the switch operates on the second layer (data link layer) of OSI, its working principle is relatively simple, while the router works on the third layer (Network Layer) of OSI ), more protocol information can be obtained, and routers can make more intelligent forwarding decisions.

(2) Data Forwarding depends on different objects

A vswitch uses a physical address or a MAC address to determine the destination address for data forwarding. A vro uses the idnumber (IP address) of different networks to determine the data forwarding address. IP addresses are implemented in software and describe the network where the device is located. Sometimes these layer-3 addresses are also called protocol addresses or network addresses. The MAC address is usually provided by the hardware and allocated by the NIC manufacturer, and has been fixed to the NIC. Generally, it cannot be changed. The IP address is usually automatically assigned by the network administrator or the system.

(3) Traditional vswitches can only be divided into conflicting domains, but not broadcast domains. vrouters can be divided into broadcast domains.

The CIDR Block connected by the vswitch still belongs to the same broadcast domain. broadcast packets are transmitted across all CIDR blocks connected to the vswitch. In some cases, communication congestion and security vulnerabilities may occur. The CIDR blocks connected to the vro are allocated to different broadcast domains, and the broadcast data does not pass through the vro. Although vswitches above Layer 3 Have VLAN functions and can also be divided into broadcast domains, communication between subbroadcast domains is not allowed, and communication between them still requires routers.

(4) The router provides firewall services.

A vro only forwards data packets of a specific address. It does not support packet transmission through the routing protocol or unknown destination network, thus preventing broadcast storms.

The switch is generally used for the LAN-WAN connection, the switch belongs to the bridge, is the data link layer equipment, some switches can also realize the third layer of the exchange. A vro is used for Wan-WAN connections. It can resolve forwarding groups between different networks and act on the network layer. They only accept the input group from one line and then forward it to another line. These two lines may belong to different networks and adopt different protocols. In comparison, vro features more powerful than vswitches, but the speed is relatively slow and expensive. layer-3 vswitches have both the ability to forward packets at the wire speed of vswitches and the good control function of vrouters, therefore, it is widely used.

At present, I am personally using ADSL for many broadband access methods. Therefore, I will give a brief description of the access to ADSL. Most of the purchased ADSL cats have the routing function (in many cases, the routing function is blocked when the manufacturer leaves the factory, because the routing function is not enabled during Telecom installation and DHCP is enabled. Enable the ADSL routing function). If an individual accesses the Internet or a few computers pass through ADSL, you only need to purchase one or more hubs or switches if the computer is large. Please purchase a vswitch because the price difference between the hub and the vswitch is very small. There is no need to pursue high prices, because product homogeneity is very serious today, and there is no problem with my cheapest switch. We recommend that you purchase an eight-port service to meet the expansion requirements. The general price is about 100 yuan. Connect all the computers to the vswitch. The only thing to do is to insert the network cable of each machine into the interface of the switch and insert the cat network cable into the uplink interface. Then you can set the routing function and DHCP to share the internet.

After reading the above explanation, you should have some knowledge about vswitches, hubs, and vrouters. The current usage is mainly based on the combination of vswitches and vrouters, the specific combination method can be determined based on the specific network conditions and requirements.