Yes, on an IPv6 address, if the prefix is ​​/64, this indicates that the first 64 bits of the IP address represent the network portion of the address. The rest of the bits, the last 64 in this case, are used to identify individual interfaces (hosts) within that network.

We explain in more detail how it works:

IPv6 Address Structure

IPv6 uses 128-bit addresses, which are generally divided into two parts:

1. Network Portion (64 bits): This part of the address identifies the unique network to which a device belongs. In a /64 prefix, this section is made up of the first 64 bits of the address.
2. Host Portion (64-bit): This part of the address is used to identify individual devices within the network. For IPv6 addresses, it is often auto-configured using the EUI-64 process, or can be assigned manually or via DHCPv6.

Meaning of the Prefix /64

• Network Administration Simplification: Using a /64 prefix is ​​a common practice that simplifies network administration by providing a clear and simple address allocation scheme, with half of the address dedicated to the network and the other half to the hosts.
• SLAAC (Stateless Address Autoconfiguration): A /64 prefix allows the use of the SLAAC mechanism, which devices use to automatically configure themselves on the network without the need for a DHCP server.
• Scalability and Security: It provides ample space for address management within a network, allowing for trillions of unique devices (2^64).

Example of an IPv6 Address with /64 Prefix

Consider the following IPv6 address: 2001:0db8:85a3:0000:0000:8a2e:0370:7334/64

• Network Portion: 2001:0db8:85a3:0000
• Host Portion: 0000:8a2e:0370:7334

In this case, the first four segments constitute the network, and the last four segments identify the specific host within that network.

The use of a /64 prefix in IPv6 is fundamentally important to ensure efficient address allocation and to facilitate various network functionalities that depend on the clear distinction between the network and host parts of the address.