Nat fundamentals and private IP

public IP Address ：

Also known as global address , It means legal IP Address , It is from NIC（⽹ Network information ⼼） perhaps ISP(⽹ Contact service providers ) Assigned address , External representatives ⼀ One or more internal local addresses , It is a global system ⼀ Can be found The address of the address .

private IP Address ：

Also called internal address , Belong to ⾮ Registered address , Specifically for the internal use of the organization ⽤. Int ⽹ Assign numbering committee （IANA） Retain the 3 block IP Address as private IP Address ：

10.0.0.0 ——— 10.255.255.255
172.16.0.0——— 172.16.255.255
192.168.0.0———192.168.255.255
Address pool ： The address pool has ⼀ Some external addresses （ Global only ⼀ Of IP Address ） Combine ⽽ become , We call this ⼀ Address sets are address pools . In the internal ⽹ The data packets of the network reach the outside through address translation ⽹ Collaterals , Will select a... In the address pool IP Address as the source of the packet IP Address , This can effectively benefit ⽤⽤ The external address of the account , carry ⾼ External access ⽹ Collateral can ⼒.

NAT Introduce

NAT Britain ⽂ The full name is “Network Address Translation”, in ⽂ intend “⽹ Network address translation ”, It is ⼀ individual IETF(Internet Engineering Task Force, Internet⼯ Process task force ) standard , allow ⼀ A whole organization with ⼀ A male ⽤IP（Internet Protocol） The address appears in Internet On . seeing the name of a thing one thinks of its function , It is ⼀ Plant the internal private ⽹ Network address （IP Address ） Translate into legal ⽹ Collateral IP Address technology

NAT classification

NAT It can be divided into three types ：

static state NAT(Static NAT)
Dynamic address NAT(Pooled NAT)
⽹ Network address end ⼝ transformation NAPT（Port-Level NAT）

static state NAT

Static transformation refers to the internal ⽹ The privacy of the network IP Address conversion to public IP Address ,IP The address is ⼀ Yes ⼀ Of , yes ⼀ Become unchangeable , Some private IP Address is only converted to some public IP Address . With the help of static conversion , Can achieve external ⽹ Collaterals on the inside ⽹ Some specific devices in the network ( Server, such as ) The interview of .

dynamic NAT

Dynamic transformation （ Also known as NAT pool） It means not to build ⽴ Internal address and global address ⼀ Yes ⼀ Fixed correspondence of .⽽ By sharing NAT Address pool IP Address dynamic building ⽴NAT The mapping relation of . Dang Nei ⽹ The host needs to enter ⾏NAT Address conversion , The router will be in NAT Select an idle global address in the address pool ⾏ mapping , Each mapping record is dynamically created ⽴ Of , At the end of the connection ⽌ Time is also taken back .

⽹ Network address end ⼝ transformation NAPT

⽹ Network address end ⼝ transformation NAPT（Network Address Port Translation） Is to map the internal address to the external ⽹ It's complicated ⼀ individual IP Different ends of the address ⼝ On . It can make ⼩ Type ⽹ Collaterals hidden in ⼀ Legal IP After the address ⾯.NAPT And Dynamic address NAT Different , It maps internal connections to external ⽹ Collateral ⼀ Separate IP Address , At the same time, add ⼀ One by one NAT The selected end of the device ⼝ Number .