A brief explanation of internal network, external network, and dynamic IP

Everyone knows that China is a country with a serious shortage of IPV4 addresses, so our dial-up broadband has always been a dynamic IP, not a fixed IP. Later, what was even more outrageous was that many cities had intranet IPs, and all our secondary IP addresses All broadband ISPs provide are intranet IPs. Intranet IPs appear more and more in our lives, so we have derived DDNS, intranet penetration, etc.
Let’s try to use a picture to illustrate the difference between internal network IP and external network IP.

What is an external network IP?

Our Internet is like a wide road, with various websites on the Internet providing The service IDC is like the various low-end businesses on the roadside. Everyone knows that retail stores are opened directly on the side of the road. Their doors face the road directly to facilitate customers' entry and exit for shopping and consumption. The house numbers 1, 2, 3 on the road... are like the external IPs. When we want to go somewhere, we can just press the house number to find it. This is the so-called external IP. For example, McDonald's on the left, 7-11 supermarket, etc.

What is dynamic IP?

Later, this road became more and more lively, and the space on the left was full (a lot of IPV4 addresses were allocated, but it was found that there were not enough ), more and more people come to this road, some do shopping and some do small business, but there are too many people and there are not so many places. What should we do? Since these people are very mobile, in order to facilitate management, we have reserved places 2 and 4 on the right side, telling those who do small business with push carts that you can only go to places 2 and 4. You are not allowed to go to other places, first come first served, there are no fixed stalls. (This is the so-called dynamic IP, first dial, first served IP, not fixed). Later, there were too many small businesses, and two seats were not enough. I often came late and found that there were no seats, so I went back. (In the early dial-up period, you could not dial a number because there was no IP address assigned to you). When a person closes his stall, a spot becomes vacant, and another stall holder happens to come, so he takes this spot and continues doing business. (When a person goes offline, the IP is freed and given to new dial-up users so that the IP address can be reused), and so on, over and over again.

What is an intranet IP?

But then the economy developed and there were so many people who wanted to do business, but there was only one spot left, No. 6, what should I do? Woolen cloth? For the sake of economic development, we build office buildings. Everyone will work in the office buildings, one room per person, and the house numbers are 101, 102, 103, 104. . . . . , These house numbers are the so-called intranet IPs.

Disadvantages of intranet IP:

As we all know, most businesses wait for people to come to their door instead of actively going to the street to attract customers, so these The businessman of the intranet IP started to advertise. I am in 101, I am engaged in beauty, and the other one is in 102, I am engaged in loans. Come quickly. (We told our friends the intranet IP and asked them to access it), but after waiting for a long time, no one came. What happened? In fact, many people who saw the advertisement were very interested, but after searching on the street for a long time, they could not find the so-called 101,102, so they had to go home. (When we directly access an intranet IP, the address cannot be found, so the packet is lost). The biggest disadvantage of the intranet is that the address cannot be found and cannot be accessed directly.

What is port forwarding?

The people in the office building looked at it and thought, this is not possible, business still needs to be done, what should I do? So I hired a receptionist and told her that if someone asks you where the beauty salon is, tell them it's 101. (Start setting up port forwarding). So I advertised again, and my business was opened. Beauty salon No. 6 on the backbone network, beauty salon No. 6 on the backbone network.

IP Address : : Port

Backbone Network No. 6 : Beauty Salon
201.113.233.111 : 80

So people arrived at No. 6 and said I was going to the beauty salon. The girl at the front desk said, go to Room 101. (The router port is forwarded to the corresponding port). If port forwarding is not set, it is like a person shouting on the 6th, I want to go to the beauty salon, I want to go to the beauty salon, I want to go to the beauty salon, no one pays attention to him, and he goes home (access failed, packet loss . )

What is port 80 blocked?

Slowly, people know that beauty salons make money, and in the future they will open a beauty salon as long as they build an office building (WEB) Server), since the original beauty salon was in Room 101, people assumed that Room 101 was the beauty salon, and no special explanation was needed. (Port 80 is the default access port for the web). However, because some people were playing tricks in the beauty salon, the administrator saw that this was no good and wanted to make things worse, so he issued an order saying that from now on, all rooms in Room 101 of the office building were not allowed to open the door, and those who wanted to open the door must undergo a review. (Port 80 is forced to be blocked, audit system is in place), and business in other rooms is normal.

How to determine whether you are using the public network or the intranet?

Check whether the local IP is consistent with the IP displayed on the website.
Consistency indicates that it is a public network IP. Inconsistency indicates that your network has been forwarded or is an intranet!

Why do you need an external IP address?

According to the poster's explanation, the office in the office building can theoretically be found, but if the front desk takes leave or goes on strike, others will not be able to find you (the intranet IP packet loss rate is high, telecommunications The provider does not provide port forwarding)

Why is it still so slow even though I have an external IP?

Having an external IP is only the first step. There are two situations that are holding us back:

In the first situation, there are people coming and going on the road, and all kinds of people. etc. In order to protect us from harm, the relevant departments set up checkpoints at every exit from the city and conducted interrogations on everyone leaving the city (the existence of the wall). Because you have to queue up for inspection, everyone's speed of leaving the city is slow (ping delay is high), and sometimes the inspector will even refuse your request to leave the city without reason (irregular packet loss increases) when the inspector sees you unhappy.

The second situation is that on specific market days, everyone rushes out of the city to buy things. The roads outside the city are not wide enough, and there are so many people that they naturally squeeze in and out, and the traffic speed slows down ( The overall international export bandwidth is insufficient, and delays increase at night and during peak periods on holidays)

So how to improve the connection speed?

Regarding the first situation, people found that the prosecutor at the exit of the city did not check all trips one by one. For example, when the neighbor Lao Wang pulled a carriage to deliver goods to the next city, he could directly let them go. pass. So you paid a little money to Lao Wang, hid in the carriage and left the city, increasing the traffic speed (corresponding to ss and other tools that cannot be described in 1000 words)

In response to the second situation, the road builder specially opened a highway Only those who can afford the high tolls can take this road, so the road is wide and there are few people. So rich people paid a lot of money to travel to and from other cities faster than usual (xx boutique network). But since I still have to pass the exit level, I still can't do some indescribable things.

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