Detailed explanation of over 255 computers in intranet IP planning

The network IP address "main" is divided into three categories of ABC, the following is the scope of coverage:

Class A: 0.0.0.0-127.255.255.255, whose subnet mask is 255.0.0.0 (another way to annotate by subnet mask is/8, which is to convert the subnet mask to binary, from left to 8 1)

Class B: 128.0.0.0-191.255.255.255, whose subnet mask is 255.255.0.0 (another way to annotate by subnet mask is/16, which is to convert the subnet mask to binary, from left to 16 1)

Class C: 192.0.0.0-223.255.255.255, whose subnet mask is 255.255.255.0 (another way to annotate by subnet mask is/24, which is to convert the subnet mask to binary, from left to 24 1)

In order to save space, and to reduce the clerical error, the following subnet masks are labeled with/x, the maximum value of X is 32, and the minimum is 0.

This also involves a subnetting problem:

If ICANN gives you 9.x.x.x, you get to be 9.0.0.0/8 such a Class A network, because the network is too big may be bad management, then you can divide the subnet, divided into 9.1.0.0/16, 9.2.0.0/16, 9.3.0.0/16 、、、 9.255.0.0/16, and then subdivided some are 9.255.1.0/24, 9.255.2.0/24 ... of course, you can split it down a little bit more.

There is also a problem with a subnet merge:

If ICANN awards you 220.220.x.x, you get the standard 220.220.0.0/24, 220.220.1.0/24, 220.220.2.0/24 、、、 220.220.255.0/24 256 Standard Class C networks, And what you need is a large network that can accommodate tens of thousands of nodes, then you can put 220.220.x.x into a network, that is, 222.220.0.0/16, it's called CIDR, we'll use this later.

The part of the plan for the private IP address area is exactly the part of ABC:

10.0.0.0-10.255.255.255 (10.0.0.0/8)

172.16.0.0-172.31.255.255 (172.160.0./16-172.31.0.0/16)

192.168.0.0-192.168.255.255 (192.168.0.0/24-192.168.255.0/24)

There are also some special 127 parts, 169 part, D Class E 224-255 part, and this topic is not

Public network IP address is a very valuable resource today, especially in China.

Then, a considerable number of enterprises, institutions, and even internet cafes, their internal LAN is also really no need to use public network IP, that is, the use of private IP address. According to the scale, a large number of enterprises have chosen the 10.x.x.x, some of the use of 172.16.x.x, a smaller number of internet cafes, used the most popular is 192.168.0.x, a standard Class C network. Note that this is just a usage habit, not a rule

Now the Internet cafes are more open, a standard C-class network has been unable to meet the capacity requirements, a lot of people say I am so, can 192.168.0.x and 192.168.1.x put into a network? Of course! The introduction of CIDR concept, it is easy to draw conclusions, 192.168.0.0/255.255.254.0, or 192.168.0.0/23, is 192.168.0.x + 192.168.1.x, if regardless of network address and broadcast address, A total of 512 nodes can be accommodated. Of course, 192.168.0.0/22, 192.168.0.0/21, 192.168.0.0/20 、、、 and even 192.168.0.0/16 are all planning methods that can accommodate more nodes.

But I personally have a bad impression of CIDR, CIDR is just a method, should not belong to a specification, this brings some compatibility problems. A few years ago when I set up RRAS in WIN2000 (SP2), there was an interface filter similar to packet filtering, and perhaps many friends had the impression that when the target network was defined, it did not recognize the network as 218.4.0.0/255.255.0.0, saying that the subnet mask was invalid, You have to manually configure the 256 target networks of 218.4.0.0/24, 218.4.1.0/24, 218.4.3.0/24 、、、 218.4.255.0/24, Because of the IP address of Class C, it only 255.255.255.0 such subnet mask, and there is like the IP address audit in IIS also has such a situation, Khan ~ ~ ~

Moreover, divide this piece in the Net bar intranet, why so many friends are asking: "Internet cafes more than 254 hosts, IP address how to stroke, such as the theme of a large, because it involves CIDR subnet after the merger of the operation, because the Network Foundation is not clearance, many friends do not understand, do not understand, do not need to understand. Looking down, I quote the theme

Why are they all crammed into the 192.168.x.x category C?

10.x.x.x (255.0.0.0) and 172.16.x.x~172.31.x.x (255.255.0.0) This is not a big world?

10.0.0.0/8 and 172.16.0.0/16-172.31.0.0/16, is not a ready-made, very good choice? Absolute compliance with the standard, absolutely not rebel through the road, some people say that such a large network must have broadcast storm and so on, this call is a bit funny. Let's not talk about what the radio storm is itself, 10.0.0.0/8 can actually hold 16,777,216 nodes, but do you really have 16777216 hosts? Broadcast volume is indeed proportional to the number of hosts in the local area network, the number of hosts can be accommodated with the LAN has no relationship, and in the Internet Café This hardware and software environment as long as the equipment and link normal and client health is not to generate a broadcast storm. Many people home ADSL broadband cats (UT300R) The default IP address is 10.0.0.138, the mask is 255.0.0.0, if you enable routing mode, then your computer also has to be set into one of the 10.x.x.x, then this large range but only two nodes of the LAN, the result of the explosion did not? Of course, if you are really worried, you can adopt 10.0.0.0/255.255.254.0, you can use the IP address is 10.0.0.0-10.0.1.255, this scheme has no problem.

You're tired of 10.x.x.x, you're tired of 172.16.x.x-172.31.x.x, and you're tired of 192.168.x.x, so I can represent ICANN to assign you a network of personalized IP addresses. Specification is just

Once again to support the "treason by leaving the road" of opinion, the Internet Café intranet with 1.1.1.x such a auspicious and good memory and personality of the network, completely feasible, side effects? Almost no, just checked. This IP is owned by General Electric Company of New Jersey, USA, do you really need to visit the company? Or do you have a customer in the Internet café who is going to work there so you have to consult their website? Of course, someone on the internet who has access to 1.1.1.x is not going to go to you, only to the real 1.1.1.x, because routers on the WAN can only listen to ICANN. If you really want the world to admit it, you start from the local telecom router, and then change the routing table, if you can.