The time for the quiz "Who is the correct answer?"In this quiz, Kenichi, Izumi -chan, and Takeda -kun answer my questions.However, only one person is correct.The theme of the quiz is "TCP/IP", the basics of network.By the way, who is the correct answer?
Who is the correct answer?(Be careful because there are two mistakes!)
IP address for special applications
In the IP address, there are several IP addresses reserved for special applications, and you can list the special applications specified in the RFC3330.Here, let's look at the special IP addresses you need to remember.
Class A's first address block "0.0.0.0/8 is a special IP address that represents "this" network. "
In fact, the network number "0" of the IP address means "THIS".That is, 0.1.2.If there is an IP address of 3/8, the network address is 0, so "No. 66051 in this network (0).1.2.3) means ".In addition, the subnet mask is set to 32 -bit..0.0.The IP address "0/32" means "this host of this network".
On the other hand, the last address block of class A is "127.0.0.0/8 is a special IP address stipulated as a loop back address.A loopback means that if you specify this IP address to the destination and send data, it will return to yourself.
The loop back address is a reserved address, and in the host with the IP, "Ping 127.0.0.You can hit the command like "1".Of course, 127.0.0.The IP packet for 1 will not be sent to the network, and will be transmitted and received within the host.Therefore, it is used to confirm that the IP function is working properly on your computer.
Private IP address
The IP address was classified into class A, B, and C depending on the size of the network.In fact, each class has a "global IP address" that can be used on the public Internet, and a "private IP address" that can be used in closed networks in companies and home.
The global IP address is an IP address for communicating on the Internet, and is an IP address that is regularly assigned by applying to a registered business reception organization called Internet Register so that it does not overlap.On the other hand, a private IP address is an IP address that can be used freely without applying.However, the use of private IP addresses is limited to local networks and is not allowed to be transmitted to the public Internet.
The address range is set for each class of A to C for private IP addresses.When using a private IP address, there is no restriction on which class should be used.You can use your favorite private IP address as needed.
However, if you use a private IP address in a company or home network, the computer will not be able to use the Internet.Because it is troublesome, the global IP address and the private IP address are actually converted on the router connected to the ISP.This is generally known by the function name "NAT (NetworkAdDress Translation)".
By using NAT, the private IP address of the internal network does not appear on the Internet as it is.Since it communicates with the global IP address set in the router to the last, it can be accessed on the Internet without any problems.
Linklocal address
In addition to private IP addresses in class B.254.0.The address block "0/16" has been reserved as a special IP address called "Link Local".
This link -locust address is used as an IP address that the computer is automatically set if the IP address cannot be automatically obtained in the DHCP protocol.Many IP networks often use private IP addresses, so if you assign a linked IP address, you will not be able to connect to the network.
Special address of class D and class E
"224.0.0.The address block of 0/4 is an address space known as class D, and its use is used as a multicast address.The main things include addresses for routing protocols such as OSPF and RIP.
Table 1 ● Special IP address (from RFC3171)
Also, "240.0.0.The address block of 0/4 is an address space known as class E, and is also a special IP address.In this address space, all 32 bits 1 "255".255.255.There is an address "255/32".This address is called a "limited broadcast", and the address of this address is "all hosts of the same network".
By the way, the local loop back address is actually specified as a special IP address, but there is no provision as a network crew back address as in Izumi's answer.In addition, Takeda -kun explains the link - -linked address, and there is no rule of Enny IP address.
It may seem surprising that Kenichi -kun's private IP address will be a special IP address, but the provisions of private IP addresses are special in the first place.So Kenichi -kun is the correct answer
This article is a special feature in the August 2007 issue of Network Magazine 1 "Who can be understood in the quiz?"TCP/IP" is re -edited.The content is in principle at the time of publication, and may be different from the present. |
