The loopback address is used by a host to send traffic to itself.
The loopback address ranges from 127.0.0.1/8 to 127.255.255.254/8.
A simple example of using the loopback address is to check whether the TCP/IP stack is working properly on a local system.
The TEST-NET uses the network block of 192.0.2.0/24 with an address range from 192.0.2.0/24 to 192.0.2.255/24.
Accordingly to RFC 3330, these addresses are to be used with domain names within vendor and protocol documentation and should not appear on the Internet.
To put simply, they can be used for teaching and learning purposes.
Most cases our computers are set to receive an IP address automatically once connected to a network, this is assuming there is a Dynamic Host Configuration Protocol (DHCP)server on the network as well with an available pool of addresses for distribution.
What if the DHCP server is not available, or down from the network? How would the operating system such as Windows compensate for the lack of a DHCP server? The Automatic Private IP Addressing (APIPA) is a feature which Windows DHCP clients use to self-assign an automatic private IPv4 address to themselves on the a network for ensure basic connectivity.
The Automatic Private IP Addressing (APIPA) scheme uses a network block of 169.254.0.0/16, with a range from 169.254.0.1/16 to 169.254.255.254/16.
Like IPv4, this new address has a format of its own.
As you can recall, an IPv4 address consist of 32-bits in length and can we written in decimal notation for easier interruption.
An IPv6 address consist of 128 bits in length and is written in hexadecimal notation.
With 128 bits, this allows IPv6 to scale to approximately 1 undecillion (1036) addresses.
An IPv6 address is made up of eight (8) hextets, each comprises of 16 bits, and this means 8 x 16 = 128 bits in length.
Since hexadecimal numbers are 0 1 2 3 4 5 6 7 8 9 A B C D E F (0 - F), each hextet ranges from 0000 – FFFF.
IPv6 uses the following concepts to support inter-connectivity with IPv4 networks:
Tunneling - Allows an IPv4 packet to be encapsulated to an IPv6 packet and vice verse.
Dual Stack - Allows both an IPv4 and IPv6 address to be assigned to a device's interface.
There are different types of addresses in IPv6, each of which has a unique purpose.
In IPv4, we called an Internet assigned address a Public address. In IPv6, we have a public address as well, however, its known as a Global Unicast address, 2000::/3.
An IPv6 link local address are in the FE80::/10 network block.
The link local address is used for local network communication only.
This means there are two (2) IPv6 addresses on an interface, 1 Global Unicast address for communication outside the local network and 1 Link-Local address communication with devices within a local network.
Just as devices uses Media Access Control (MAC) address to communicate within a Local Area Network (LAN), in an IPv6 network the Link-Local address functions the same way.
One communication be beyond the local network, the Global Unicast address is used.
The link local address has the same functionality as the link local address in the IPv4 address space.
However, in the IPv6 space, the link local address is ::1/128. This means only the first bit is 1 in the entire address.
Unlike IPv4, the IPv6 link local address is a single address.
This type of address has the similarity of a private IPv4 address and is really limited to your network, FC00::/7.
This type of address is shared between multiple devices , however the transmission of a message is sent to the closet device based on geographic location.
This address is used by a group devices:
Assigned FF0s::/8
Solicited Node FF02::1:FF00:0000/104
This process uses a client’s 48-bit Ethernet MAC address, and inserts another 16 bits in the middle of the 48-bit MAC address to create a 64-bit Interface ID.
Unicast - This is a one-to-one transmission between a sender and a receiver on a network. Used in both IPv4 and IPv6 networks.
Multicast - Allows a single device to communicate with with many devices but not all on the same network. Used in both IPv4 and IPv6 networks.
Anycast - This type of communication is used only on an IPv6 network, the transmission of a message is sent to the closet device based on geographic location.
Broadcast - This type of communication occurs on IPv4 networks which allows the transmission of a message to be sent to all devices on the same IP network.