How do you write an IPv6 address?

What is my IPv6 network address?

Your IPv6 address is an IPv6 prefix that represents your entire IPv6 network, but it does not specify the actual network interfaces (IPv6 addresses). Instead, the prefix specifies the routing interface of your IPv6 network (that is, your default router) and the broadcast domain (that is, the broadcast address). A prefix can be either /64 or /56 (64 or 56 bits) in length, but your prefix length cannot exceed /66. For example, /65 indicates a prefix of /65 = 65 (65 bits) bits.

For example, the IPv6 address for the network 192.168.0/64 is 2001:0DB8:C00D::1. Your default router is 2001:0DB8:C00D::1, and the broadcast domain is 2001:0DB8:C00D::2. Because /64 is a /65 prefix, you can have a maximum of 66 networks (66 bits /64).

What is my IPv6 address and how do I get it? This section covers how to get your IPv6 address and provides examples of other IPv6 address prefixes that you might see. The following sections help explain the most common prefixes. For information about IPv6 addresses that do not follow these standard prefixes, see IPv6 Other Addresses.

The /64 Prefix. The most common prefix is /64. It is used to describe a class C IPv6 subnet that has a maximum of 64 hosts. It is represented by the string ::ffff:0/64. This represents the following values:

/64 = 0 (0 bits). 1 (128 bits). 2 (256 bits). 3 (512 bits). 4 (1024 bits). 5 (2048 bits). 6 (4096 bits). 7 (8192 bits). Note that the most significant bit of this value is reserved. The reserved bit is always 1. Therefore, /64 always has a length of 128 bits, and each of the lower 64 bits is significant.

For example, the address 2001:0DB8:C00D::1 represents the network 2001:0DB8:C00D::1/128.

How do you write an IPv6 address?

This may be the most popular question in my entire history of writing, ever.

It's not rocket science - the Internet Engineering Task Force has outlined an approach to writing addresses, and many operating systems already understand it. If your IPv4-enabled app or system uses only local interfaces, you should be able to use an IPv6 version of your address.

However, if you're an operating system, web server, mail server, database, or similar product that supports both IPv4 and IPv6, what do you do when one client or user asks for an address using a deprecated protocol? I'm about to explain how we can do that. What's the worst thing that could happen? The worst thing that could happen is to drop some packets, with no other consequences than that you might lose the occasional visitor. It's important to be pragmatic. There are hundreds of thousands of companies on the Internet that can and should support IPv6, yet they've only just begun. And there are plenty of reasons why that's not going to happen any time soon.

If we want to save lives, we need to start a mass IPv6 deployment, and get the world off of the dangerous bridge. That means we need to take the risk of losing a few occasional visitors today, rather than waiting around until the world is fully IPv6-ready.

Why you probably aren't interested in IPv6 yet. Here's why most operating systems aren't ready for a true mass deployment of IPv6: You can use a private interface (your LAN) or a public interface (for the Internet). This is done by setting an appropriate local scope - either link-local scope or site-local scope. So for a private interface, you'd use '::/64' to cover the entire link-local range. And for a public interface, it would be '0.0/0'.

(your LAN) or a public interface (for the Internet).