In this video, you will learn to, describe the structure of the IPv6 address schema, describe an IPv6 header, describe what is meant by Unicast, Multicast, and Anycast in IPv6 addressing schemes. >> Let's talk about IPv6. We've covered extensively in the previous videos that IPv4 addresses were 32 bits long. Remember the discussions about the address being four eight bit octets. Since the world is running out of IP addresses using IPv4 protocol, the latest version of the IP protocol, IPv6 extends the address length from 32 bits to 128 bits. We're going to be dealing with hex numbers now, so refer back to the first video in the lesson, if you need a refresher. An IPv6 address being 128 bits long, is four times longer than the 32 bit IPv4 address. But that does not give us only four times as many addresses. In the first video in this lesson, we learned that 2 the 32nd power gives us just under 4.3 billion possible addresses. Well, 2 to the 128th power in decimal format is about 3.4 times 10 to the 28th power. Which, according to Wikipedia would be called 34 octillion. I'm getting a bit off topic again, but that's a very big number, like the number of atoms in an elephant big. An IPv6 address is divided into eight four-digit hexadecimal values, each separated by a colon as shown here. Each single hexadecimal digit can have 16 possible values, which makes it a four-bit long binary. So a group of four hex numbers would be 16 bits. And there are eight of these in the IPv6 address, so 8 times 16 brings us up to 128 bits. There are a few rules to remember when representing an IPv6 address. An IPv6 address is not case sensitive. You don't need to specify leading zeros in the address, and you can use a double colon to represent any number of consecutive zeros. So for example, instead of writing 0:0:0:0:0:0:0:1, we'll use ::1. Of course to keep it interesting, there is one exception to this rule. You can only use the double colon replacement once in an IPv6 address. This is an example of an IPv4 header. You should remember the version, time to live, protocol, source IP address and the destination IP address. This is an example of an IPv6 header, it actually has fewer fields. The first field of course, is the version. Here is the source IP address, but instead of being 32 bits long, it's 128 bits long, as is the destination address. There are three different types of addressing schemas allowed in IPv4, unicast, broadcast and multicast. In unicast mode, one computer communicates with just one other system. In broadcast mode, one computer communicates with all of the other systems on that same subnet. You may remember that the network portion of the broadcast address is the same as the network portion of every other computer on that subnet. But the host portion has all the bits turned on or set to 1. This ensures that the packet will be sent to all of the endpoints on the subnet. Multicast is a one to many arrangement. A group of systems can subscribe to a multicast address, so, anything sent by that address will be received only by the systems that are subscribed to receive multicast from that system. In IPV6, things are a little different. Unicast and multicast are essentially the same but broadcast has been replaced by anycast. An IPv6 anycast address is an address that's assigned to more than one interface. Typically, the address belongs to different endpoints. A packet that is sent to an anycast address is routed to the nearest interface that has that address. So, that is the basics of the IP protocol. I hope this makes sense to you and you can now see both the similarities and the differences between the IPv4 and IPv6 addressing. Thank you.