ADSL Modem routing function details and application skills introduction
At present, most ADSL Modems support multiple network protocols and have static routing functions, which can be regarded as a complete router. I often encounter users who buy ADSL Modem, specify that Modem must have a routing function, ask the reason, the answer is often the performance of Modem with routing function is better. In fact, many people's understanding of the ADSL Modem routing function only stays in concept. So, in a small network, how does the ADSL Modem with routing function communicate with other devices? What specific role does the routing modem have on the network? How can we use the routing function of ADSL Modem? Below, the author will discuss the topic of ADSL Modem routing function with you in several installments.
1. Overview of IP routing IP router definition
The Internet is a huge collection of networks and hosts interconnected by routers. Routers are dedicated computers that connect two or more packet-switched networks. When the router is working, it can actively receive data for a specific target device, but where will the data be transmitted next after receiving the data? After you define the IP routing rules for the router, the router will use the rules you provide to determine the data to be transmitted to the next target device.
2. Comparison of IP router and telephone exchange
The working principle of an IP router is somewhat similar to a wired switch that handles telephone calls. When we dial a telephone number, the request signal is first connected to a working telephone exchange through our local telephone line, and all the outgoing calls reach this main exchange first; if the telephone number you dialed is this If it is outside the service area of ​​the main switch, then this switch will connect to the higher level switch for long-distance calls, and this higher level switch will check the area code you dialed and connect you to the call. The local telephone exchange; this remote exchange will check the prefix of the telephone number you dialed (the first three digits), and connect to a switch that matches the telephone number prefix; to the last exchange, it will Check the last four digits of the phone number and connect it to the phone you want to connect to.
In contrast, when your computer starts to communicate with other hosts on the network on the Internet, for example, to connect to a web server to browse the web, your computer sends out the computer's IP address including the target web page (like "phone number" ") Packets, all your requests first arrive at the router of the ISP connected to your computer (like the" first telephone exchange "), then the ISP router will check the network ID part of the destination IP address of the packet (Like "telephone area code"), and determine the next router to send the web browsing request; after several such routers, the request reaches the router of the target network, and then this router analyzes the host ID part of the target IP address, Send the request to the computer to be accessed.
Comparing computers and telephones, all processing is initially sent to the same router or switch. It is used as a gateway for other higher or lower-level devices. No device can know the data departure and End the path, but each device uses a specific part of the target address (or phone number) to determine which device it wants to connect to in the next step.
Tip: Each IP address contains two kinds of information, a network ID and a host ID. The network ID is used to distinguish a specific network number in the Internet or corporate LAN; the host ID is used to distinguish a specific computer or device. The first part of each IP address contains the network ID, and the other parts contain the host ID. The length of the network ID is determined by the level of the network.
3. Skip and gateway
Whenever a packet on the Internet passes from one Internet address to another Internet address (that is, this packet goes through a "step". A "step" can be on different ports on the same device, on the same network The data transfer process between different devices or a device on other networks), it needs to use the gateway. The gateway is an IP address provided to users of the network on a certain network. For example, when a computer on your LAN requests access to a company ’s website, your ISP server is like a gateway to the Internet. Once your request reaches the destination, the gateway allows you to access the company ’s web server Page.
4. Use IP router to specify default gateway
IP routers can specify on their computers, routers, and other machines that use IP addresses which gateway they use to transfer packets to their destination. If a target file does not determine the IP route, then its data will be sent to the default gateway that has been preset. This gateway serves the transmission of data like a higher-level telephone switch. The destination device, but it can "smartly" recognize which device can send the packet. If it cannot determine which device can send the data (because no route is specified), then the machine will send the data to its default gateway. Eventually, a high-level machine will use its predetermined IP route to transmit data along the transmission path to the target device of the data packet
Below, will continue to introduce the application of ADSL Modem routing function.
Do I need to set up IP routing
In a typical home or office local area network, in the following cases, in order to make the ADSL Modem and the Internet provide a suitable path, we need to set its IP routing.
If there are more than two networks or subnets in our network system, routers are used in both networks, and communication is required between each other; if our network is more complicated, there are more than two ISPs connected Server; or when we want to connect to a remote local area network (such as home network and office network). In such cases, it is possible to set up a router in the network.
Viewing the IP routing table Each computer and router that uses an IP address has an IP routing address table that it often uses to surf the Internet. For each target IP address, the starting IP address for obtaining data is listed in the address table. The router determines how to forward the packet by checking its routing table. If the destination address of the packet is on the network directly connected to the router, the router can submit the packet without using another router; if the destination address is on the remote network, the router must Forward the packet to another router closer to the destination network, and then the next router is responsible for forwarding and delivery. The route to the remote network can be statically configured or dynamically obtained through some routing protocols.
Enter the configuration page of ADSL Modem, click the "Routing" tab, and then click "IP Routing" in the task bar to display the IP routing table (see the attached picture). There is a row for each active route in the IP routing table, including the preset route in the ADSL Modem, the route you have added, and the route automatically obtained by connecting to your ISP network.
In the routing table, there are several items of "destination address, subnet mask, NextHop, interface name, Route Type, Route Origin, operation". Below I will explain the meaning and function of some of the parameters.
â— Target address: Specify the IP address of the target computer. The destination address may be the IP address assigned to a specific computer or a complete network, or the default IP address of the next router.
â— NextHop: In the destination address displayed in the "Destination Address" column, the address specified by "NextHop" is used as its next destination IP address for transmitting data packets.
â— Interface name: refers to the interface through which the data packet is transmitted to its next specific network segment.
â— Routing type: refers to whether this router is a direct route (Direct) or an indirect route (Indirect). In a direct route, the source computer and the target computer are on the same network, and the router sends the data directly from the source computer to the target computer. In indirect routing, the source computer and the target computer are in different networks. If the router needs to transfer the data to another network, it needs more routers to process it.
â— Route Origin: Refers to what kind of routing mode. Dynamic routing (Dynamic) refers to the route preset by your ISP or manufacturer on the system. With dynamic routing, the router can choose an optimal path among the large number of available routes between networks. In the case of static routing (StaTIc), the network administrator must enter the address of each destination network and associated next hop one by one in the router. The route you created is marked as "Local". Other routes can be created automatically or remotely through various network management protocols.
â— Operation: You can click the trash can icon to delete the corresponding middle route entry.
The IP routing table may also show your ISP's default gateway for Internet communication.
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