Computers talk to each other through the TCP/IP protocol, and different computers can accurately find each other through IP addresses . Information interaction between computers that are not on the same network is achieved through gateways . The gateway is a public network address issued by the operator, and the DHCP server issues the IP address. IP addresses are sent to each computer through the DHCP service ports UDP67 and UDP68.
1. Switch
Each computer has an IP, how to connect them together?
This means calling a network device a "switch". The function of a switch is to connect different computers together through network cables . They can be connected physically, just like wires connected through electric switches.
It is a kind of network device. It can make multiple computers connected to it form a local area network , and if there is a proxy server, it can also achieve simultaneous Internet access. It does not have the function of routers to automatically identify the sending and arriving addresses of data packets, but it has a higher transmission speed than HUB, because it can simultaneously transmit data packets to all computers connected to it, and all computers share its bandwidth rate. That is, a bandwidth of 100M. No matter how many computers are connected, the bandwidth of each computer theoretically reaches 100M.
There is no dial-up function inside the switch . The function of a switch is to divert network signals so that more computers can connect to the Internet and share the Internet.
Switches are different from routers. Switches generally have at least 8 ports . We only need to connect one of the 1-4 ports in the router to any port of the switch with a network cable , and the other ports of the switch can be connected to many computers to achieve Internet access. Yes, in this way, a network cable can be connected through a router combined with a switch to achieve more than 4 people sharing the Internet. The function of the switch here is equivalent to adding network cable ports, which can be understood as shunting, one becomes N ports .
Switches are generally used for LAN-WAN connections . Switches are classified as bridges and are devices at the data link layer. Some switches can also implement third-layer switching. Routers are more powerful than switches, but they are relatively expensive and not as fast as switches.
2. Router
Once a computer has an IP address, it can interact with a network host. If it wants to interact with other network hosts
, it must go through a gateway, which is the so-called router . A router is a specific implementation used to connect to external networks.
The router login interface is to enter the router IP in the browser, which is generally 192.168.1.1. You must ask clearly when you buy this, otherwise you will not be able to enter the setting interface. Before doing this, you need to set your computer IP to the same gateway, that is, 192.168.1.X, where X is any number between 2-255. Only in this way can you enter the routing login interface. Generally, the routing login account password is admin. It is best to ask when you buy it. After entering the setting interface, you can set up the router. If you are using broadband (ADSL) access, select "ADSL Virtual Dial-up".
Dial-up Internet access can be realized inside the router, and then shared with multiple computers to access the Internet at the same time .
The router has 5 ports, one of which is the WAN port, which is connected to the broadband line , and the other four ports are used to connect to computers with Internet access. In other words, a router can support up to 4 computers to share the Internet.
The router has routing functions , a network relay system , and a switching function . In addition to the WAN port , the other four ports of the router are equivalent to switching ports . The router is used for WAN-WAN connections and can solve the problem of forwarding between heterogeneous networks. Grouping, acting on the network layer;
3. Cat Modem
A modem is a computer hardware that translates a computer's digital signals into analog signals that can be transmitted along ordinary telephone lines , and these analog signals can be received by another modem at the other end of the line and translated into A language that computers can understand
. This simple process completes communication between two computers. Telephone lines transmit analog signals, while PCs transmit digital signals. The cat is an ADSL access terminal. That is to say, when the network uses telephone lines, it must go through the modem to connect to the PC.
It translates the computer's digital signals into pulse signals that can be sent along an ordinary telephone line. These pulse signals can be received by another modem at the other end of the line and translated into a language that the computer can understand.
The information in the computer is a digital signal composed of "0" and "1", but what is transmitted on the telephone line can only be analog electrical signals. Therefore, when two computers want to transmit data through a telephone line, a device is needed to perform digital-to- analog conversion .
It is mainly used for data communication in telephone networks and plays an important role in network interconnection and remote access.
4. Summary
A switch can connect multiple computers. The computers interconnected with the switch have the function of communicating with each other and form an internal LAN . However, access to the Internet requires network support , so one end of the switch needs to be connected to a router . The router It can realize switching function, dial-up, realize broadband connection, and allocate broadband resources to switches, so that multiple computers can share the Internet .
Only when the IP address segments of the ADSL Modem, broadband router, and local connection are unified, mutual access and data transmission can be achieved! If the IP is already in the same IP segment, there is no need to set it. Otherwise, you need to change the router IP so that it is in the same IP segment as the cat IP. After the settings are completed, save and restart.
5. LAN (Local Area Network)
The LAN port refers to the local area network interface, which is mainly used to connect the router to the local area network. The LAN interface is mainly used for the home internal network and is mainly connected to the switch, hub or PC in the home network . Different network devices have different interface types. Common LAN interfaces mainly include AUI, SC and RJ-45 interfaces.
6. WAN (Wide Area Network)
The WAN port refers to the wide area network interface. The WAN interface is mainly used to connect to the external network . For example, the interface in the router that connects to the Internet to transmit data uses the WAN interface. Common WAN interfaces include E1, V.24, V.35, ATM and POS interfaces.
7. The difference between LAN and WAN
(1) The network cable connection methods for the WAN port and LAN port on the LAN broadband router are different.
Plug the access network cable provided by the network operator into the WAN port, then connect several computers sharing the Internet to the LAN port , log in to the management interface of the router with one computer and perform corresponding configurations to complete the shared Internet access .
(2) The transmission process of network data is different between the WAN port and the LAN port.
When a machine in the network sends a data packet to the external network , it first sends a request to the default gateway , that is, to the broadband router. When the router analyzes the internal IP address in the packet, it will check the NAT address translation table of the device itself. After finding the corresponding entry, the WAN port IP address will be used to communicate with the external network .
(3) "Router IP address" and "port IP address" are actually the IP addresses of the router's WAN port and LAN port. They are both port IP addresses. It's just that the two ports are connected to different networks. When configuring the address of the router You have to enter the port configuration.
LAN is the IP of the router's local area network, routing distribution, and you can also set it yourself. WAN is the IP of the wide area network, given by the operator, and is a dynamic IP.
8. VLAN (Virtual LAN)
VLAN is a virtual local area network. It is a group of logical devices and users. These devices and users are not restricted by their physical locations and communicate with each other as if they are on the same network segment, hence the name.
9. WLAN (wireless local area network)
WLAN is the abbreviation of Wireless Local Area Network, which refers to the application of wireless communication technology to interconnect computer devices to form a network system that can communicate with each other and realize resource sharing. The essential characteristic of wireless LAN is that it no longer uses communication cables to connect computers to the network, but connects wirelessly, making network construction and terminal movement more flexible.
10. VPN (Virtual Private Network)
The function of a virtual private network (VPN) is to establish a dedicated private network on a public network and then conduct encrypted communications. It is widely used in enterprise networks. VPN gateway achieves remote access by encrypting data packets and converting the destination address of the data packets. VPN can be implemented through servers , hardware, software and other methods.
