What is an IP address?

IP Introduction

Every host (Host) on the Internet has a unique IP address. The IP protocol uses this address to transfer information between hosts, which is the basis for the Internet to run. The length of the IP address is 32 bits, divided into 4 segments, each segment is 8 bits, expressed in decimal numbers, each segment ranges from 0 to 255, and segments are separated by periods. For example, 159.226.1.1. The IP address consists of two parts, one is the network address and the other is the host address. IP addresses are divided into 5 categories: A, B, C, D, and E. The two most commonly used ones are B and C. An IP address is like our home address. If you want to write to a person, you need to know his or her address so that the postman can deliver the letter. A computer sending information is like a postman. It must Knowing the unique "home address" will prevent letters from being sent to the wrong person. It's just that our addresses are expressed in words, and the computer's address is expressed in decimal numbers.

As we all know, in telephone communications, telephone users are identified by their telephone numbers. Similarly, in order to distinguish different computers on the network, it is also necessary to assign a number to the computer. This number is the "IP address".

Edit this paragraph What is an IP address?

The so-called IP address is a 32-bit address assigned to each host connected to the Internet.

According to the TCP/IP (Transport Control Protocol/Internet Protocol, Transmission Control Protocol/Internet Protocol) protocol, IP addresses are represented in binary. Each IP address is 32 bits long. Bits are converted into bytes, which is 4 bytes. For example, an IP address in binary form is "00001010000000000000000000000001". It is too laborious for people to process such a long address. In order to facilitate people's use, IP addresses are often written in decimal form, with the symbol "." in the middle to separate different bytes. Therefore, the above IP address can be expressed as "10.0.0.1". This representation of IP addresses is called "dotted decimal notation", which is obviously much easier to remember than 1 and 0.

Some people may think that a computer can only have one IP address. This view is wrong. We can specify a computer to have multiple IP addresses, so when accessing the Internet, do not think that one IP address is one computer; in addition, through specific technologies, multiple servers can also use one IP address. The server looks like a host to the user.

After dividing the IP address into two parts, the network number and the host number, the designer must decide how many bits each part contains. The number of digits in the network number directly determines the number of networks that can be allocated (calculation method 2^number of digits in the network number); the number of digits in the host number determines the maximum number of hosts in the network (calculation method 2^number of digits in the host number-2) . However, since the network size contained in the entire Internet may be relatively large or relatively small, the designers finally cleverly chose a flexible solution: dividing the IP address space into different categories, each category has a different network number digits and host number digits.

Edit this paragraph to assign an IP address

The TCP/IP protocol requires different settings for different networks, and each node generally requires an "IP address" and a "subscriber". Netmask", a "Default Gateway". However, you can use Dynamic Host Configuration Protocol (DHCP) to automatically assign an IP address to the client, avoiding errors and simplifying the settings of the TCP/IP protocol.

So, how does the LAN allocate IP addresses? IP addresses on the Internet are uniformly managed by an organization called "IANA" (Internet Assigned Numbers Authority, Internet Network Number Assignment Agency).

Edit What is the IP address of this paragraph?

——IP is currently a popular technology. A number of new terms related to this, such as IP network, IP switching, IP telephony, IP fax, etc., have also appeared one after another. So, what is IP?

——IP is the abbreviation of the English Internet Protocol, which means "the protocol for interconnection between networks", which is also a protocol designed for computer networks to connect and communicate with each other. In the Internet, it is a set of rules that enable all computer networks connected to the Internet to communicate with each other. It stipulates the rules that computers should abide by when communicating on the Internet. Computer systems produced by any manufacturer can interconnect with the Internet as long as they comply with the IP protocol. It is precisely because of the IP protocol that the Internet has rapidly developed into the world's largest and open computer communication network. Therefore, the IP protocol can also be called "Internet Protocol".

——How does IP realize network interconnection? Network systems and equipment produced by various manufacturers, such as Ethernet, packet switching network, etc., cannot interoperate with each other. The main reason why they cannot interoperate is because of the basic unit of data they transmit (technically called "frame"). The format is different. The IP protocol is actually a set of protocol software composed of software programs. It uniformly converts various "frames" into "IP datagram" format. This conversion is one of the most important features of the Internet, enabling all kinds of computers to All can achieve interoperability on the Internet, that is, they have the characteristics of "openness".

——So, what is a "datagram"? What are its characteristics? Datagrams are also a form of packet switching, which means that the transmitted data is segmented into "packets" and then sent out. However, unlike traditional "connection-type" packet switching, it is "connectionless". Each "packet" (group) is sent out as an "independent message", so it is called "data". "Report". In this way, there is no need to connect a circuit before starting communication, and each datagram is not necessarily transmitted through the same path, so it is called "connectionless". This feature is very important as it greatly improves the robustness and security of the network.

- Each datagram has two parts: header and message. The header contains necessary content such as the destination address, so that each datagram can accurately reach the destination without going through the same path. . Reassemble and restore the original sent data at the destination. This requires IP to have the functions of packet packaging and collection assembly.

——During the actual transmission process, the datagram must also be able to change the length of the datagram according to the packet size specified by the network it passes through. The maximum length of the IP datagram can reach 65535 bytes.

——There is another very important content in the IP protocol, which is that every computer and other device on the Internet is assigned a unique address, called an "IP address". Because of this unique address, it is ensured that users can efficiently and conveniently select the objects they need from thousands of computers when operating on connected computers.

——Now the telecommunications network is integrating with the IP network. New technologies based on IP are popular technologies. For example, the technology of using IP network to transmit voice (VoIP) is very popular. Others such as IP over ATM, IP over SDH, IP over WDM, etc. are all the focus of research on IP technology.

IP address types

When the Internet was originally designed, in order to facilitate addressing and hierarchical network construction, each IP address included two identification codes (ID), namely the network ID and Host ID. All hosts on the same physical network use the same network ID. A host on the network (including workstations, servers, routers, etc.) on the network has a host ID corresponding to it. IP addresses are divided into 5 types according to different network IDs: Class A addresses, Class B addresses, Class C addresses, Class D addresses and Class E addresses.

Edit this IP address classification

1. Class A IP address

A Class A IP address consists of a 1-byte network address and a 3-byte host address. The highest bit of the network address must be "0", and the address range is 1.0.0.1-126.255. 255.254 (binary representation is: 00000001 00000000 00000000 00000001 - 01111110 11111111 11111111 11111110). There are 126 Class A networks available, each of which can accommodate more than 16 million hosts.

2. Class B IP address

A Class B IP address consists of a 2-byte network address and a 2-byte host address. The highest bit of the network address must be "10", and the address range is 128.1.0.1 -191.254.255.254 (binary representation: 10000000 00000001 00000000 00000001 - 10111111 11111110 11111111 11111110). There are 16,382 Class B networks available, and each network can accommodate more than 60,000 hosts.

3. Class C IP address

A Class C IP address consists of a 3-byte network address and a 1-byte host address. The highest bit of the network address must be "110". Range 192.0.1.1-223.255.254.254 (binary representation is: 11000000 00000000 00000001 00000001 - 11011111 11111111 11111110 11111110). There are more than 2.09 million Class C networks, and each network can accommodate 254 hosts.

4. Class D addresses are used for multicast (Multicast).

The first byte of the Class D IP address starts with "lll0", which is a specially reserved address. It does not point to a specific network. This type of address is currently used in multicast (Multicast). A multicast address is used to address a group of computers at a time. It identifies a group of computers that share the same protocol.

Address range 224.0.0.1-239.255.255.254

5. Class E IP addresses

Begin with "llll0" and are reserved for future use.

An all-zero ("0.0.0.0") address corresponds to the current host. The IP address with all "1"s ("255.255.255.255") is the broadcast address of the current subnet.

Which organization assigns the IP address in this paragraph?

All IP addresses are uniformly assigned by the international organization NIC (Network Information Center). Currently, *** all over the world There are three such network information centers.

InterNIC: responsible for the United States and other regions;

ENIC: responsible for the European region;

APNIC: responsible for the Asia-Pacific region.

To apply for an IP address in my country, you must go through APNIC, which is headquartered at the University of Tokyo, Japan. When applying, you should consider which type of IP address to apply for, and then submit it to a domestic agency.

Edit this paragraph What are public addresses and private addresses?

The public address (Public address) is responsible for the Inter NIC (Internet Network Information Center). These IP addresses are assigned to organizations that register and apply to Inter NIC. Direct access to the Internet through it.

Private address (Private address) is an unregistered address and is exclusively used within the organization.

The reserved internal private addresses are listed below

Class A 10.0.0.0--10.255.255.255

Class B 172.16.0.0--172.31.255.255

Class C 192.168.0.0--192.168.255.255

Edit this paragraph to reserve the IP address

When the Internet was originally designed, in order to facilitate addressing and hierarchical structure Network, each IP address includes two identification codes (ID), namely network ID and host ID. All hosts on the same physical network use the same network ID. A host on the network (including workstations, servers, routers, etc.) on the network has a host ID corresponding to it. IP addresses are divided into 5 types according to different network IDs: Class A addresses, Class B addresses, Class C addresses, Class D addresses and Class E addresses.

There is a cmd command to find IP: tracert followed by ip address, you can check the route passed!

Edit which IP addresses are available in this LAN

In a LAN, there are two special IP addresses, one is the network number and the other is the broadcast address. The network number is the address used for Layer 3 addressing, which represents the entire network itself, and the other is the broadcast address, which represents all hosts on the network. The network number is the first address in the network segment, and the broadcast address is the last address in the network segment. These two addresses cannot be configured on the computer host. For example, in a network segment such as 192.168.0.0 255.255.255.128, the network number is 192.168.0.0 and the broadcast address is 192.168.0.127. Therefore, in a LAN, the addresses that can be configured in the computer are two fewer (network number, broadcast address) than the addresses in the network segment. These addresses are called host addresses. In the above example, only host addresses 192.168.0.1 to 192.168.0.126 can be configured on the computer.

Edit this paragraph IPV4 and IPV6

The existing Internet runs on the basis of the IPv4 protocol. IPv6 is the next version of the Internet protocol, which can also be said to be the protocol of the next generation of Internet. It was originally proposed because with the rapid development of the Internet, the limited address space defined by IPv4 will be exhausted, and the lack of address space will inevitably lead to hinder the further development of the Internet. In order to expand the address space, it is planned to redefine the address space through IPv6. IPv4 uses a 32-bit address length, and there are only about 4.3 billion addresses, which are estimated to be allocated between 2005 and 2010, while IPv6 uses a 128-bit address length, which can provide almost unlimited addresses. According to a conservative estimate of the actual addresses that can be allocated to IPv6, more than 1,000 addresses can be allocated per square meter of the entire earth. In the design process of IPv6, in addition to solving the address shortage problem, it also considered other issues that were not solved well in IPv4, mainly end-to-end IP connections, quality of service (QoS), security, multicast, and mobility. , plug and play, etc.

Compared with IPv4, IPv6 mainly has the following advantages. First, the address space is significantly expanded. IPv6 uses a 128-bit address length to provide an almost unlimited number of IP addresses, ensuring the possibility of end-to-end connectivity. Second, it improves the overall throughput of the network. Since IPv6 data packets can far exceed 64k bytes, applications can take advantage of the maximum transmission unit (MTU) to obtain faster and more reliable data transmission. At the same time, the routing structure is improved in design and simplified header length is adopted. Structure and a more reasonable segmentation method enable routers to speed up data packet processing and improve forwarding efficiency, thus improving the overall throughput of the network. Third, the overall service quality has been greatly improved.

The service level and flow tag in the header can achieve priority control and QoS guarantee through router configuration, thus greatly improving the quality of IPv6 service. Fourth, security is better guaranteed. The use of IPSec can provide effective end-to-end security guarantees for upper-layer protocols and applications, and can improve security at the router level. Fifth, support plug-and-play and mobility. When the device is connected to the network, it can automatically obtain the IP address and necessary parameters through automatic configuration, achieving plug-and-play, simplifying network management and easily supporting mobile nodes. And IPv6 not only borrows many concepts and terminology from IPv4, it also defines many new features required to move IPv6. Sixth, the multicast function is better implemented. The "scope" and "flag" are added to the multicast function of IPv6, which limits the routing range and can distinguish between permanent and temporary addresses, which is more conducive to the implementation of the multicast function.

At present, with the rapid development of the Internet and the continuous improvement of Internet users' requirements for service levels, IPv6 will receive more and more attention around the world.

How to know the IP address when editing this paragraph 1

: Check QQ user IP address

1. Check through FolkOicq

FolkOicq is a tool that can A program to add IP display patches to QQ, the latest version is FolkQQ0530SE_B2. After downloading, you will get a Zip compressed package, use Winzip to extract the file QQ2000.EXE, and copy it to the QQ installation directory (before doing this, it is best to back up the original QQ2000.exe to prevent future errors that cannot be restored). Then run QQ2000, click on an online user, and you will find that there is an IP address under the QQ number.

2. Check through IpSniper

IpSniper is an IP address query tool for QQ2000. It supports all current versions of OQ2000 and can work normally under Win98 and Win2000 operating systems. When you run the IpSniper program for the first time, a dialog box will pop up asking you to set various parameters in "Settings". Click "Settings", specify the directory and file name where the QQ executable file is located, and click "OK". The next time you run IpSniper, the QQ main program will be started directly. When you are talking to a friend or stranger, IpSniper will intercept the caller's IP address, port number and the other party's QQ number in real time, and display the geographical location of the other party.

3. Check the IP through the firewall

Since QQ uses the UDP protocol to transmit information, and UDP is a connectionless protocol, in order to ensure that the information reaches the other party, QQ needs the other party Send an authentication to tell this machine that the other party has received the message. Firewalls (such as Skynet) have UDP monitoring functions, so we can use this authentication to check the IP. Haha, it takes no effort at all!

Now let us give a practical example to see how to use Skynet to check IP.

Step 1: Turn on UDP monitoring of Skynet firewall;

Step 2: Send him or her a message;

Step 3: Check the QQ server address you are using, in this case it is 202.104.129.252;

Step 4: Exclude the QQ server address and determine the other party’s IP address, in this case it is 61.133.200.90;

What about it? He (she) can’t run away, right? Too much trouble? You must know that Tencent's QQ upgrade speed is faster than Rockets. There are always version restrictions when using the first two methods. Using this method can be done once and for all!

4. Check IP through NetXRay

NetXRay is a software for advanced packet error detection developed by Cinco Networks. It is very powerful.

Using such a powerful weapon to check QQ’s IP is a bit overkill.

Step 1: Run NetXRay and select tools→Matrix in the menu

Step 2: Select the IP label that appears at the bottom.

Step 3: Right-click and select Show Select Nodes in the pop-up menu

Step 4: Open QQ and chat with the person you want to check while observing the window. The data line that changes color at the moment the data packet is sent is the IP connection between you and him. Look at the other end of the data cable. The IP address (61.138.121.18) is what you have been dreaming of.

There are several ways to use NetXRay to check the IP address of QQ users. You can try the other methods yourself

There are many methods and tools to check the IP addresses of QQ users. , the methods introduced here are enough for you. If it doesn't work, it's easy to find some tools in this area.

2. Check the IP in the chat room

1. Use IP Hunter

IP Hunter is a software developed by Dugu Swordsman. The method to use IPHunter to check the IP in a chat room is as follows: In a chat room that allows posting pictures and playing music, use HTML language to send pictures and music to the other party. If you set the path of the picture or music file to your own IP, then even though this URL The picture or music file at the address does not exist, but as long as you send it to the other party, the other party's browser will automatically access your IP. Different formats may be used for different chat rooms, but you only need to set the path to your IP. The example description is as follows:

For example: "*** Chat Room" sending format is as follows:

To send an image: img src="IP address, just type the command in the DOS window "ping www.sina.com.cn", you can see the IP.

2. Use the tool to check

Let's take Cyber ??Assassin II as an example. /p>

Cyber ??Assassin II is a Chinese network security detection software specially designed for security professionals produced by Tianxing. Run Cyber ??Assassin II, enter the main interface, and select "IPlt;-gt;" under the "Toolbox" menu. Host Name", a dialog box appears, write the other party's domain name in the box below "Enter IP or Domain Name" (we assume the other party's domain name www.sina.com.cn here), click the "Convert to IP" button, the other party The IP comes out and is 202.106.184.200.

5. Query and set the IP address of the machine

Start -gt; Run -gt; cmd -gt; ipconfig /all

You can query the IP address of this machine, as well as subnet mask, gateway, physical address (Mac address), DNS and other details.

You can set the IP address of this machine through: Network Neighborhood -gt; Properties -gt; TCP/IP and you can start setting up

6. Planning considerations for local area network IP addresses

As public network IP addresses become increasingly scarce. , small and medium-sized enterprises often can only get one or a few real Class C IP addresses. Therefore, only dedicated (private) IP address segments can be used in the enterprise's internal network. When choosing a dedicated (private) IP address, you should pay attention to the following. Several points:

1. Assign a Class C IP address segment to each network segment. It is recommended to use the 192.168.2.0--192.168.254.0 segment IP address.

Since some network devices (such as broadband routers or wireless routers) or applications (such as ICS) have the function of automatically assigning IP addresses, and the default IP address pool is often located in the 192.168.0.0 and 192.168.1.0 segments, therefore, before using this IP address segment, it is often easy to cause IP address conflicts or other failures. Therefore, unless necessary, you should try to avoid using the above two class C address segments.

2. The subnet mask of the Class C address can be used. If necessary, a variable-length subnet mask can be used. Under normal circumstances, do not use an excessively large subnet mask, and the number of computers in each network segment should not exceed 250 computers. The greater the number of computers on the same network segment and the greater the number of broadcast packets, the more effective bandwidth is lost and the lower the network transmission efficiency.

3. Even if you choose 10.0.0.1--10.255.255.254 or 172.16.0.1--172.32.255.254 IP addresses, it is recommended to use 255.255.255.0 as the subnet mask to obtain more IPs network segments and keep each subnet with a smaller number of computers. Of course, if necessary, variable length subnet masks can be used to appropriately increase the number of computers that can be accommodated.

4. Assign an independent IP address segment to the management VLAN of the network device to avoid address conflicts with the management IP of the network device, thereby affecting the implementation of remote management. For the same reason, all servers must be divided into an independent network segment.

It should be noted that do not think that assigning different IP addresses to computers on the same network can improve network transmission efficiency. In fact, computers on the same network are still in the same broadcast domain, and the number of broadcast packets will not be reduced due to different IP addresses. Therefore, just specifying different network segments for computers cannot achieve the purpose of dividing broadcast domains. If you want to reduce the broadcast domain, the most fundamental solution is to divide VLANs and then assign different IP network segments to each VLAN.