Reserved address in IP address

Reserved IP address Assignment
The unification of IP addresses on the Internet is managed by an organization called the IANA (Internet Assigned Numbers Authority, internet network number distribution agency). Depending on the purpose and security level, IP addresses can also be broadly divided into two categories: public and private addresses. Public addresses are used in the Internet and can be accessed freely in the Internet. Private addresses can only be used on the internal network and only through a proxy server to communicate with the Internet.

An institutional network must request a public IP address to connect to the Internet. However, given the special circumstances of network security and internal experiments, three zones are reserved exclusively as private addresses in IP addresses, and their address ranges are as follows:

network category	ip address range	network number
a class network	10.0.0.0~10.255.255.255	1
b class network	172.16.0.0~172.31.255.255	16
c class network	192.168.0.0~192.168.255.255	255

A network that uses a reserved address can only communicate internally, not with other networks. Because the reserved address in this network may also be used by other networks, if the network interconnection, then the search for routes will be due to the address is not unique problems. However, these networks with reserved addresses can interconnect with external networks by translating the reserved addresses in the network into public addresses. This is also one of the important ways to ensure network security.

Reserved IP address segments are not used on the Internet, so routers connected to the WAN will simply discard the packet when processing the reserved IP address, instead of being routed to the WAN to isolate the data from the reserved IP address inside the LAN.

In the case of less than 254 computers in the LAN, it is generally possible to select the IP address range in the Class C IP address segment, such as from "192.168.1.1" to "192.168.1". 254 ".

Special IP Address
Just like each of us has an ID number, every computer on the network (or, more specifically, the network interface of every device) has an IP address to mark itself. We may all know that these addresses are made up of four bytes, dotted decimal notation and their a,b,c classification, however, in the total of approximately Chiceae available IP addresses, do you know the following common special meaning addresses? Let's take a look together:

First, 0.0.0.0

Strictly speaking, 0.0.0.0 is not a real IP address. It represents such a collection: all unclear hosts and destination networks. The "unclear" here means that there is no specific entry in the local routing table to indicate how to get there. For this machine, it is a "shelter", all do not know the "three No" personnel, are sent in. If you set a default gateway in your network settings, the Windows system automatically generates a default route with the destination address of 0.0.0.0.
Second, 255.255.255.255

Restrict broadcast addresses. For this unit, this address refers to all hosts within the network segment (the same broadcast domain). If translated into human language, it should be: "Everyone in this room is paying attention!" "This address cannot be forwarded by the router.
Third, 127.0.0.1

Native address, primarily for testing. In Chinese, it means "myself". In a Windows system, this address has an alias of "Localhost". Addressing such an address, it is not possible to send it to the network interface. Packets with the destination address "127.0.0.1" should never appear on the transport media unless there is an error.
Iv. 224.0.0.1

Multicast address, note the difference between it and the broadcast. This is the address from 224.0.0.0 to 239.255.255.255. 224.0.0.1 refers to all hosts, 224.0.0.2 refers to all routers. Such addresses are used in a number of specific programs and multimedia programs. If your host turns on the IRDP (Internet Routing Discovery Protocol, use multicast feature) feature, then you should have such a route in your host routing table.
Wu, 169.254.x.x

If your host uses DHCP to automatically obtain an IP address, the wingdows system assigns you an address when your DHCP server fails, or the response time is too long to exceed the time specified by a system. If you find that your host IP address is a sort of address, unfortunately, it is possible that your network is not functioning properly.
Liu, 10.x.x.x, 172.16.x.x~172.31.x.x, 192.168.x.x

Private addresses, which are used in a large number of enterprise internal networks. Some broadband routers also tend to use 192.168.1.1 as the default address. Private networks may use arbitrary IP addresses because they are not connected to the outside. Such addresses are reserved for use in order to avoid confusion of addresses when accessing the public network in the future. Private networks that use private addresses, when connected to the Internet, use address translation (NAT) to translate private addresses into common legal addresses. This type of address is not present on the Internet.

For a host on a network, it can normally receive the legitimate destination network address has three kinds: The local IP address, broadcast address and multicast address.

Reserved address in IP address