Getting older, not necessarily wiser!
In this post we will dive a bit deeper into Internet protocol version 6. This is where things can get a bit confusing, at least that was my experience when trying to figure it out.
I am taking a different tact from many of the articles and videos I have watched on the subject. So, for this post forget everything you know about IPV4. We will focus on IPV6, and I will not be discussing how it is similar or different from IPV4.
In the last post we discussed how IPV6 uses a 128 bit address space but is represented by eight four octet colon separated groups of hexadecimal numbers.
Each number is a hexadecimal (base 16) number with a range from 0 to f, where letters represent numbers past 9. For example A is 10, B is 11, and F is 15. Since there are eight four octet groups, this comes to thirty two total numbers in the IPV6 address.
If we convert each number to binary (base 2), each single number becomes four digits long. If we multiply thirty two by four, we get one hundred and twenty eight. This is what is meant by a 128 bit address.
When we start talking about IPV6 address space, we will be doing a lot of bit counting. This will be done from left to right. And we will use a slash notation tacked onto the end of the address. For example, if we are talking about the left most sixteen bits, we will represent this as “/16”.
Your devices IPV6 network adapter can and will have multiple IPV6 addresses. The exact number will depend on your network setup. If you are activity connected to the Internet, you will have at least two to three IPV6 addresses. You may have additional addresses, depending on the local network you are plugged into.
The reasons for this will become apparent when we talk about IPV6 address types. The important thing to remember is you can have multiple addresses.
There is one more thing we need to talk about before diving into dissecting an IPV6 address. And that is the destination type for our communications.
Unicast: This is a one to one communication sent from one device directly to another device.
Multicast: This is a one to many communication sent from one device to more than one device. These devices must be specifically named.
Anycast: This is a little different. You can have multiple devices with the same Anycast address. When your device sends information, it will go to the closest Anycast address. If that device is down, your device will find the next closest Anycast address. This is good for backup servers. One goes down, you simply go to the next one in line.
Broadcast: This is a one to every device. This is different than Multicast, in that you specify the targets for Multicast. Broadcast sends it to everyone and everything.
Remember or slash notation. When I use something like “/3” this means the first three bits starting at the left. The next entry will continue from the previous. For example /23 would start at bit 4 and go to bit 23.
In this post we have covered some of the definitions and information related to an IPV6 address. In the next post we will work through some examples of the different types of IPV6 addresses. We will also look at how many IPV6 addresses you could have assigned and why you would have them.
Networking: 10,000 foot View IPV6 Part 2