In IPv6, prefixes are written using a format that specifies the base address of the network followed by a forward slash and the number of bits in the netmask.

This format is commonly known as CIDR (Classless Inter-Domain Routing) notation.

IPv6 Prefix Notation Example:

Let's say you have a network prefix that spans the first 64 bits of addresses on that network. The notation would be something like this:

• 2001:0db8:85a3::/64

In this example:

• 2001:0db8:85a3:: represents the base address of the network. The double colon (::) indicate a series of segments of consecutive zeros, which is a compression feature in IPv6 to simplify writing addresses that contain long blocks of zeros.
• final match. indicates that the first 64 bits of the address are used to identify the network. This leaves the remaining bits to identify individual hosts within that network.

Notation Details:

• Separation by two points: IPv6 uses a colon (:) to separate each block of 4 hexadecimal digits. Each block represents 16 bits, and a full IPv6 address has 128 bits.
• Zero compression: IPv6 notation allows compression of blocks of zeros to simplify and shorten addresses. Blocks of consecutive zeros in one direction can be replaced by ::, but this compression can only be used once in one direction to avoid ambiguity.

This format is essential for configuring IPv6 networks, as it clearly defines how addresses are divided between the network ID and the devices (hosts) within that network, which is crucial for routing and network management. .