2019 tutorials: VPN for IPv4 Address Types and their Use

Purpose: unicast addresses are provided for the use in the Internet. Each packet

header consists of different fields; two of them contain the unicast destination ad-

dress and the unicast source address. This allows the specific exchange of packets

in both directions (e.g. to send a request to a destination and receive a response

from there).

"This host on this network"

Value: 0.0.0.0/8

Purpose: addresses of this address block refer to all stations of the same network.

The "This host on this network" address also means all IP addresses of the same

station. If a computer has no IP address assigned it may use the "This host on this

network" address as source address for requests to DHCP servers. The "This host

on this network" address in address filters identifies all stations of the same

network. Another application relates to routes to other networks. The address

„0.0.0.0" designates the default route to other networks.

Loopback Address

Ranges: 127.x.x.x/8

Purpose: a loopback address should be used for loopback requests of higher layer

software to an IP address of this range within the same system. It may be used for

ICMPv4 echo requests (command „ping") to test the operation of the IPv4 soft-

ware of the same computer (ATTENTION: the physical network port cannot be

tested!).