A detailed analysis of the application of the route function of ADSL Modem

Edit comments:Most ADSL Modem supports multiple network protocols and provides static routing functions, which can be regarded as a complete router. I often encounter many users who specify that the Modem must have the routing function when purchasing the ADSL Modem. The answer is often that the Modem with the routing function has better performance. In fact, many people only have a conceptual understanding of the ADSL Modem routing function.

Currently, most ADSL Modem supports multiple network protocols and provides static routing functions, which can be regarded as a complete router. I often encounter many users who specify that the Modem must have the routing function when purchasing the ADSL Modem. The answer is often that the Modem with the routing function has better performance. In fact, many people only have a conceptual understanding of the ADSL Modem routing function.

In a small network, how does the ADSL Modem with the routing function communicate with other devices? What is the specific role of the route Modem on the network? How can we use the routing function of ADSL Modem? Next, I will discuss with you about the ADSL Modem routing function in several phases.

I. Overview of IP routing

1. IP router Definition

The Internet is a large collection of networks connected through routers and hosts. Routers are dedicated computers that connect two or more packet exchange networks. When a router is working, it can actively receive data for a specific target device, but after receiving the data, what will it send to next? After you define an IP routing rule for a vro, The vro uses the rule you provide to determine the target device to which the data is transmitted.

2. Comparison between IP Routers and Telephone Switches

The working principle of the IP router is similar to that of the wiring switch that handles telephone calls. When we dial a telephone number, the request signal is first connected to a working telephone switch through our local telephone line, and all the calls made reach the main switch first; if the phone number you dial is outside the service area of the main switch, the switch will connect the long-distance call to a higher-level switch, this higher-level switch will check the dialing area code and connect you to the telephone switch in the called area; this remote switch checks the prefix of the phone number you dial (the first three digits) and connects to a switch that matches the phone number prefix; to the last switch, it will check the last four digits of the phone number and connect to the destination phone number you requested to connect.

In contrast, when your computer starts to communicate with other hosts in the network over the Internet, such as connecting to a website server to browse webpages, your computer sends data packets containing the IP address of the computer on the target webpage (like a "phone number, all your requests first arrive at the ISP router (like the "first telephone switch") connected to your computer, at this time, the ISP's router will view the network ID of the destination IP address of the data packet (like the "telephone area code"), and determine the next router that sends the Web browsing request. After several routers, the request arrives at the vro of the target network, and then the vro sends the request to the computer to be accessed by analyzing the host ID of the target IP address.

Compared with computers and telephones, all processing is initially sent to the same vro or vswitch. It serves as a gateway for other higher or lower-layer devices, no device can know the start and end paths of the data, but each device uses a specific part of the target address (or phone number) to determine which device is connected next.

Tip: Each IP address contains two types of information: network ID and host ID. The network ID is used to distinguish a specific network number in the internet or enterprise LAN; host ID is used to distinguish a specific computer or device on the network. The first packet of each IP Address Contains the network ID, and the other part contains the host ID. The length of the network ID is determined by the network level.

3. Skip and gateway

Whenever a data packet on the Internet passes through another Internet address from one Internet address (that is, this data packet goes through a "Skip" step ". A "Hop" can be a data transfer process between different ports on the same device, different devices on the same network, or one device on another network ), it requires a gateway. A gateway is an IP address that is provided to users on a network. For example, when a computer on your LAN requests access to a company's website, your ISP Server is like a gateway for the Internet. Once your request reaches your destination, the gateway allows you to access the webpage on the webpage server of the company.

4. Use an IP router to specify the Default Gateway

IP routers can specify which gateway they use to send data packets to the destination on computers, routers, and other machines using IP addresses. If an IP route is not determined for a target file, its data will be sent to the preset default gateway, which serves as a data transmission service like a higher-level telephone switch, it may not deliver data packets to the destination device, but it can "intelligently" identify which device can send data packets. If it cannot determine which device can send data (because no route is specified), the machine will send the data to its default gateway. In the end, a high-level machine uses its predefined IP route to transmit data along the transmission path to the target device of the data packet.