What kind of IP address is an invalid IP address?

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In a valid IP address, each three-digit number is between 0 254, and it cannot be greater than 254 or even 255. This is a legitimate IP address, and there are IP addresses with Class A, B, and C IPs.

IPv4 IP addresses are all (1 255).（0~255）.（0~255）.(0 255).

The IP address range for Class A is, the IP address range for Class B, and the IP address range for Class C.

In a Class A IP address, the length of the network identity is 8 bits, the length of the host ID is 24 bits, and the subnet mask is class, which is suitable for medium-sized networks.

The length of the network identity is 16 bits, the length of the host identity is 16 bits, and the subnet mask is suitable for small-scale local area networks, where the length of the network identity is 24 bits, the length of the host identity is 8 bits, and the subnet mask is.

And in every legitimate IP address, there are 4 3-digit digits with ". ."Separated numbers, and each three-digit number is between 0 and 255, and contains the number 255.

Legal analysis: IP address is converted from 8-bit base base to decimal system, 8-bit base base, the maximum is 11111111, converted to decimal 255, so any IP address, as long as there are numbers greater than 255 in the IP, it is an error address. The length of the IP address is 32 bits (there are 2 32 IP addresses in total), divided into 4 segments of 8 digits each, expressed in decimal numbers, each segment has a range of 0 255 digits, and the segments are separated by periods.

Legal basis: "Rules of Procedure of the National People's Congress of the People's Republic of China" Article 22 The sessions of the National People's Congress use modern information technology to promote the digitization of meeting documents and materials, and use the Internet to provide convenience and services for deputies in the performance of their duties.

First of all, each network segment in the network has two special addresses that cannot be used, that is, the so-called illegal addresses. The first is the starting IP address of the network segment, i.e., this address represents the network segment itself. The other address is the end address of the network segment, for example, this address represents the broadcast address of the network segment.

Broadcast address. Several other addresses, the first is a broadcast address, and the fourth is a network segment address. As for the third, the IP address uses 8-bit binary, so the maximum digit is 255 and the third point quantile of 294 is wrong.

In the second part, the IP type is examined here, that is, Class A addresses and Class B addresses. Let's talk about the answer first, the illegal address is 11101110 10101011 .

01010100 .00101001。This address is converted to dot decimal system.

is a Class D address. Class D addresses are currently reserved addresses and are used for hostgroup addressing when multicasting. This probably knows that he has a reserved address.

Specific Class A addresses, Class B addresses can be visited. I won't talk about it when the phone is out of battery. 1. Reverse detection technology.

Scan the IP to see if it has opened the ports that are often opened by the 80, 8080 and other ** servers, obviously an ordinary user IP is unlikely to open the above ports.

2. x forwarded for http header

The IP address with http** enabled can be identified by this method; If it comes with XFF information, the IP is undoubtedly an **IP.

3. Keep-alive packets.

If a keep-alive packet with a proxy-connection is present, the IP address is undoubtedly the ** IP address.

4. Check the port on the IP address.

If an IP has a port greater than 10,000, then most of the IP is also problematic, and it is almost impossible for an ordinary home IP to open such a large port.

Almost all of these four IP detection methods are public, and some large companies will take other methods to avoid malicious IPs. For example, the use of web crawlers to crawl **IP and mark it, and even worse, it will collect malicious IPs through business modeling, and then judge whether these IPs are **IPs through protocol scanning.

There are a lot of words on it, donkey's lips are not on the horse's mouth.

The question asks the correct IP address of the host, which means that this address should be the IP address assigned to the computer.

A and C are wrong because these two addresses are network segments, in the case of the default 24-bit subnet mask, their host bits, that is, the last group of numbers are 0, not a detailed address, just like we send express delivery only wrote the provinces and cities, not write which building which unit, it is impossible to find the specific location, so it can not be used as a valid host address.

D is wrong because the number 256 cannot appear, the IP address is a 32-bit binary number, every 8-bit group, divided into 4 groups, if all 8 bits are 1, converted to decimal is only 255.

B is right, because even if the last three sets of numbers are all 111, it looks special, but each set of numbers is within 255, and the host bit is also within 254, so it is a configurable IP address.