Introduction to IPv6

Ipv6 uses a hexadecimal format. The IP addresses are 128bits in length with each digit representing 4 bits. The IP addresses are divided into 8 16bit blocks separated by a : 

An IPv6 address is split into two parts network portion and the host portion each portion having 64bits.

2001:0001:0000:0000:0000:0000:0000:0001

Secondly the first 48 bits are ISP based the next 16 are the subnet portion and the final 64 is again the host portion. 

2001:0001:0000:0000:0000:0000:0000:0001

Omitting zeros

In Ipv6 leading zeros can be omitted and trails of zeros can be replaced by a double colon like below.

2001:0001:0000:0000:0000:0000:0000:0001 can be reduced to 2001::1/64

Dual stack

In the UK it is common for us to use both Ipv4 and IPv6 together, this is called dual stack.

Common IPv6 addresses

Link-local IPv6 addresses are a type of IPv6 address that are used for communication between devices on the same network segment. These addresses are automatically assigned to network interfaces when IPv6 is enabled and can be identified by their prefix, which is "fe80::/10".

Link-local addresses are important because they allow devices to communicate with each other on a local network without the need for a global, routable IP address. This means that devices can communicate with each other even if they are not connected to the internet or a larger network.

One of the benefits of using link-local addresses is that they are automatically generated by devices, which means that network administrators do not need to manually assign addresses to each device on the network. Additionally, link-local addresses are not subject to the same address exhaustion issues as global IPv4 addresses, which can be a problem in networks with a large number of devices.

Unique link local addresses are similar in function to private IPv4 addresses, which are used within a local area network (LAN) and are not routable on the public internet. Unique local addresses are also known as site-local addresses, although this term is deprecated in favor of ULA.

Unique local addresses have the prefix "fc00::/7" and are divided into two parts: a 40-bit global ID and a 16-bit subnet ID. The global ID is used to create a unique address within a site or organization, while the subnet ID is used to identify individual subnets within the site.

One of the benefits of using unique local addresses is that they are globally unique, meaning that they will not conflict with any other addresses on the internet. This is because the global ID portion of the address is generated using a pseudo-random number generator, ensuring that the address is unique within a site or organization. Additionally, unique local addresses can be used without the need for coordination with an internet registry or service provider.

Global IPv6 addresses are used for communication on the internet. These addresses are globally routable and can be used to communicate with devices anywhere on the internet.

Global IPv6 addresses have a 128-bit address space, which is much larger than the 32-bit address space used in IPv4. This allows for a much larger number of unique addresses, which is important as the number of devices connected to the internet continues to grow.

Global IPv6 addresses have the prefix "2000::/3" and are divided into two parts: a 48-bit global routing prefix and a 64-bit interface ID. The global routing prefix is assigned by an internet registry or service provider and identifies the network to which the device is connected. The interface ID is unique to each device and is typically based on the device's MAC address.

One of the benefits of using global IPv6 addresses is that they are globally routable, meaning that devices can communicate with each other anywhere on the internet. This makes it easier for devices and services to communicate with each other without the need for complex address translation mechanisms.