How Broadband Routers Work

Broadband routers, as a network sharing device, are increasingly appearing in our lives, work, and study. Because of their many advantages such as convenient networking, security and reliability, and support for a variety of popular broadband access methods, more and more families and SOHOs with multiple computers will choose broadband routers when sharing the Internet. However, I believe that many users have never understood the principle of Internet access. Today, we will introduce the two issues of broadband router sharing Internet access principle and whether to choose broadband router or proxy server software in detail.

Working principle of broadband router

Broadband routers cannot be completely called routers from an accurate definition. This type of product can only realize some of the functions of traditional routers. Many manufacturers hope that users can accept their broadband router products more and call them routers. This is a multi-physical port NAT conversion product that provides shared access for broadband access users. We all know that proxy server software also uses NAT conversion technology, but broadband routers are specially designed for broadband lines, using independent processor chips and software technology to achieve NAT conversion. Therefore, compared with the traditional use of proxy server software to share the Internet, broadband routers have many incomparable advantages.

Here we mentioned NAT conversion technology several times. In fact, this technology is the most basic and core technology of broadband routers. Its principle of sharing Internet access is NAT conversion technology. Let us introduce NAT conversion technology to you.

NAT is the full name of Network Address Translation. This technology is mainly used in the network to solve the shortage of public IP addresses. The working principle of NAT is to convert the internal private network address into a legal public network address so that the Internet can be accessed.

In the TCP/IP protocol, we need to understand two types of IP addresses. One is the public IP address that can directly access the Internet, and the other is the private IP address that we most often use when we build a local area network. For example, the IP address 192.168.0.1 is a private address. It is not unique in the global network and can be used in any network in the world. The public IP address is unique in the global network. It is like the street and house number in major cities around the world. It mainly serves to identify different networks. In the Internet, it is precisely because of such public IP addresses that our communication can be realized.

However, due to the increasing consumption of public IP address resources, it is impossible for us to apply for many public IP addresses in one network that can directly communicate on the Internet. At this time, we will use NAT address translation technology, which can convert private addresses such as 192.168.0.x in the local area network into IP addresses that can be used on the Internet. In this way, the purpose of accessing the Internet is achieved.

In the working mode of NAT, four IP addresses are involved:
Inside Local IP address: The host address assigned to the internal network, which is globally unique but a private address.
Inside Global IP address: A legal IP that represents one or more internal IPs to the outside world.
Outside Global IP address: A legal IP of an external network host.
Outside Local IP address: The host address of the external network, which appears to be a private address of the internal network.

Click to see full image

Through the connection diagram above, we can basically understand the location of these four addresses in the network. Let's give you an example to illustrate how NAT is implemented: In Adan's local area network, there is an internal private address 192.168.0.x, and this network has only one exit, which is the router named adan. This router has an internal global address 218.246.29.18, which can be a static IP address provided by a telecom operator or obtained dynamically. In short, this global address uses a legal public IP address.

When the internal host needs to access the Internet, the internal host will send a data packet to the default gateway, which is the router with a public IP address. At this time, the source address carried by the data packet is the private IP address 192.168.0.x. When receiving this data packet, the router will check its own NAT address translation table. When the corresponding entry is found, it will replace the private IP address in the data packet with the address 218.246.29.18. The data packet will use the address 218.246.29.18 to access the external network!

Well, through the above understanding, we have a preliminary understanding of NAT technology. Now we will explain the principle of broadband router sharing Internet access

.

Router port diagram

Generally, broadband routers have WAN and LAN ports. The WAN port is used to connect to the broadband line. This port uses the public IP address provided statically or dynamically by the telecom operator, while the LAN port is used to connect to the PCs in the local area network. These PCs use private IP addresses dynamically assigned by the DHCP protocol or manually assigned. In fact, these two addresses correspond to the Inside Local IP address and Inside Global IP address of the NAT technology mentioned above.

Click to see full image

Generally, when setting the IP address of the PC in our local area network, there will be an option of a default gateway. This option refers to the host that the PC needs to point to by default when sending a data packet to the external network. In this environment, it is what we call the internal network IP address of the broadband router, which is generally 192.168.0.1.

When user A in the local area network needs to send a data packet to the external network, this machine will send a request to the default gateway. When this data packet reaches the broadband router, the broadband router will decompose the data packet, extract the source IP address information of the header of the data packet, and then compare it with the entries in the NAT address mapping table to find the corresponding entry. At this time, there will be a conversion process. The broadband router will replace our internal network address with the public IP address provided by the telecom operator according to the settings, and re-encapsulate our data packet with this address. At this time, this data packet will use this public network IP address to transmit through the Internet.

When the other network receives this data packet, the decomposed source IP address is the public network IP address. The other party can make a corresponding response based on this address, and the destination IP address used in this response is the public network IP address. By using this IP address, the response packet will be sent to our broadband router. At this time, the broadband router will perform another conversion to convert the destination address to the internal network address, so that the data packet can reach the host in our LAN.

Choose broadband router or proxy server software

From the above, we can see that broadband routers use NAT technology. If we consider speed completely, using a PC as a proxy server is actually better than the NAT forwarding performance of broadband routers. Many readers here will ask, why don’t we use proxy servers to share the network, so that we don’t need to invest in buying broadband routers? Here we will answer this question for you again.

1. Broadband routers can provide more functions

In addition to the NAT conversion function, the broadband routers sold on the market now also integrate many other security and manageability functions, such as parent management function and DHCP dynamic address allocation function. The proxy server is inferior in these functions. Therefore, for some home users who only need to share the Internet, we can use proxy server software, while in some SOHO and other environments with higher requirements, we still recommend using broadband routers. For example, many telecom operators now use the method of binding MAC addresses to IP addresses to prevent users from sharing the network. If you want to break this restriction when using proxy server software, it is difficult to do so. Broadband routers can provide MAC address cloning function, which can easily break this restriction to share the Internet.

2. The proxy server requires a host to provide sharing services for the network

This is a big drawback of the proxy server, because the proxy server requires a host to provide sharing services for our network. When the proxy server is shut down, the host in the LAN cannot obtain sharing services. As a broadband router sharing Internet access, any host in the LAN will not affect the Internet access needs of the internal network when it is turned on and off. This is actually a big advantage of broadband routers.

3. When more than two PCs share the Internet, the broadband router is the first to bear the brunt. When

more than two PCs share the Internet, if you use proxy server software, we need to invest in a switch or hub device. The price of an eight-port switch on the market is about 60 yuan, and now many broadband routers are less than 100 yuan, and the switching module is integrated into the broadband router. The author believes that it is more appropriate to invest in a broadband router.

From the above three points, we can see that we choose broadband routers because they are convenient for sharing Internet access, suitable for a variety of broadband lines, and can obtain more functions. Therefore, when setting up a small network for sharing Internet access at home and SOHO, we still recommend that you buy a broadband router of about 100 yuan.

Summary:

Above, we have introduced the principle of broadband router sharing Internet access and based on this principle, we choose broadband routers and proxy server software. Through this article, everyone should have some understanding of the sharing principle of broadband routers, and it will be helpful to users who are preparing to set up home networks and SOHO networks. I hope it will be helpful to you as well.