/ 64 - prefix length. This is the number of bits in the address that is fixed. Thus, a / 64 indicates that the first 64 bits of a 128-bit IPv6 address are fixed. The remaining bits (in this case 64) are flexible and you can use all of them. This means that when your ISP gives you / 64, it gives you 2 64 addresses (i.e. 18 446 744 073 709 551 616 addresses).
There are several common prefix lengths for IPv6. A / 64 is the size of one LAN. As a client, you often receive / 56 (256 LAN) or / 48 (65 536 LAN) from your Internet service provider. You can then create several LANs that need / 64 each.
The exact number depends on the circumstances and the choice of provider. In the data center, one / 64 is enough for simple deployment with one VLAN or with one server (possibly with virtualization). Deploying data centers with multiple LANs (for example, uplink VLANs for a firewall, DMZ and one or more Internet networks, or for a VPN concentrator) requires more than / 64. Live connections (DSL, FttH, etc.) Often receive / 56 or / 48, so the subscriber can have several local networks (home, office, guests, etc.). Business connections always get / 48 so they can use the available space to create a good addressing / numbering plan.
Edit: Looking at your example again, I see that you explicitly specify the last 64 bits of the address. It may also mean that your ISP has provided you with one IPv6 address in the common / 64 (local area network) the ISP is working with.
Sander steffann
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