Special and private IPv4 addresses

0.0.0.0

• Non-routable IP address
• Has different meanings in different contexts:

In the context of the client computer this means that the computer is not connected to any TCP/IP network.

In the context of a routing table, this means that the IP is 0.0.0.0 with the default subnet mask as also 0.0.0.0

This means that packets directed towards this address will be redirected to the default gateway.

255.255.255.255 — broadcast IP address:

Any computer in the same broadcast domain can get the message with this special IP address as the destination.

Loopback IPv4 addresses

In class A, IP addresses — 127.0.0.0–127.255.255.255 or 127.0.0.0/8. There are a total of 2²⁴ ~=16million IP addresses for this purpose. What a waste!! These are referred to as loopback addresses that facilitate communication from these addresses to these addresses. It’s like a person talking to himself. These loopback addresses are used to check if the NIC is functioning properly.

Link-Local Address

Any address from 169.254.0.0–169.254.255.255 or 169.254.0.0/16 is referred to as a link-local address. These are self-generated automatically —

• When a host can’t find a DHCP server (Dynamic Host Configuration Protocol).
• When an error occurs between the communication of a host and a DHCP server.

A link-local address also means:

• It is non-routable(the device can’t access the internet)
• The host can communicate with devices on the same LAN like a printer.

Private Address

• Non-routable addresses. As routers would not deliver packets with private IP addresses.
• Free to use within a private network without any permission.

Some private IP addresses are:

• Class A — 10.0.0.0–10.255.255.255 or 10.0.0.0/8
• Class B— 172.16.0.0–172.31.255.255 or 172.16.0.0/12
• Class C— 192.168.0.0–192.168.255.255 or 192.168.0.0/16

Devices with private IP addresses can’t connect to the outside internet directly(Security). Instead, a router or some device capable of Network Address Translation has to be used.