Question

Discuss the Global unicast, unique local and link local addresses of IPV6. Your answer must provide comparisons with IPV4 public and private addresses.

What is NAT and why it is utilized in IPV4?

Answer 1

Global unicast:

This is equivalent to IPV4 public addresses.In IPv6,global unicast is a globally routable public IP address and the device which uses this can wrap to and fro anything else from the internet.We can easily identiy global unicast bracuse they all come from same prefix which means the first three bits are going to be same for all global unicast addresses

Global unicast addresses start with 2000::/3 (hex 2 or 3). They consists of two parts:

subnet ID – 64 bits long. Contains the site prefix (obtained from a Regional Internet Registry) and the subnet ID

interface ID – 64 bits long. It acts like the IPv4 host field and is typically composed of a part of the MAC address of the interface.

Link-Local address:

It is exact opposite of global unicast address.These are non-routed IP addresses and they send packets to other devices on the same link only.They are assigned to a single interface and they all come from the same range.These have the prefix FE80::/10 meaning that the first 10 bits of a link-local address will always be the same as the first 10/ highest order bits in FE80.In IPv4 it is equivalent to 169.254.0.0/16.

Unique local address:

These are the same as IPV4 private addresses.these are not routable over the internet.They are meant to be used on a private network sector.Like Global Unicast IPv6 addresses, Unique Local addresses also have a global scope. But the scope of Unique Local addresses are defined by organizations by routing topology and filtering policies at the site boundary level.Unique Local IPv6 addresses can be viewd as globally unique private routable IPv6 addresses, which are typically used inside an organization.

Locally Defined Addresses: FD00::/8

Centrally Assigned Addresses: FC00::/8

NAT(Network Address Translation):

NAT is used in routers.It is used to translate a set of IP addresses to another set of IP addresses.NAT helps preserve the limited amount of IPV4 public IP addresses.Engineers developed private IP addresses and NAT to prevent the shortage of IP addresses.Private IP addresses will be translated by NAT into public IP addresses.NAT also translates a public address to private address. In other words, a single public IPv4 address can be used for hundreds, even thousands of internal private IPv4 addresses.

NAT includes four types of addresses:

1.Inside local address

2.Inside global address

3.Outside local address

4.Outside global address

When determining which type of address is used, it is important to remember that NAT terminology is always applied from the perspective of the device with the translated address:

Inside address - The address of the device which is being translated by NAT.

Outside address - The address of the destination device.

NAT also uses the concept of local or global with respect to addresses:

Local address - A local address is any address that appears on the inside portion of the network.

Global address - A global address is any address that appears on the outside portion of the network.