IP address

IPv4

Special IPs:

• 0.0.0.0

  Non-routable meta address.

  Used to designate Invalid, unknown targets.

  Also used as host to listen up to all public IPs. (flask run -h 0.0.0.0)

• 127.0.0.1

  one of loopback address (starting from 127) used to establish connection with the same machine.

• localhost

  Usually point to 127.0.0.1

  Defined in /etc/hosts:

  127.0.0.1 localhost
  ::1 localhost // ipv6
  

IPv6

128bit

NAT (Network Address Translation)

用于缓解IPv4不足，指的是路由器自动修改IP报文实现LAN/WAN之间转换的过程。