IP is Internet Protocol which is one of the major protocols that run the Internet. A protocol is a set of rules that say how people or devices behave and communicate. In the case of IP it is used to carry data across the Internet from one device to another and includes a method of how devices are addressed similar to how the street name and number of your house are determined.
We have been using version 4 of IP since about 1980 and it is referenced usually as IPv4. It had addresses that looked like 192.168.7.13 In the late 90s as the Internet and World Wide Web rapidly expanded it was discovered that there were not enough addresses in IPv4 for all the computers. At that time several methods were developed to stretch the addresses and NAT was one popular way of only having one address for the network that was recognized on the Internet and using addresses that were only recognized in the network but not on internet in the private network). Development of Internet Protocol version 6 (usually called IPv6) began at that time and slowly began implementing soon after 2000.
IPv6 is replacing IPv4. Ipv6 was originally developed in the late 90s as we ran out of IPv4 addresses. However with NAT and other methods the life of IPv4 was extended.
However in the past year IANA has run out of IPv4 addresses although the regional issuing authorities have not yet. With the Internet of Things or the Internet of Everything we have a much larger need for IP addresses.
Dual stacking is what is often currently occurring and will occur for the foreseeable future. Dual stacking is where your network adapter works with both IPv4 and IPv6.
In the header in the IP packet several fields have new names in IPv6. Next header field is the protocol of the data. What was TTL is now hop limit.
Now for the number of addresses that are available. There are 340 undecillion addresses which means about 50 billion billion billion addresses per person in the world. That should last us a while.
The addresses are hexadecimal numbers in the format xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx with each x being a hexadecimal number and in IPv4 we called them octets in IPv6 each group of 4 may be referred to as a hextet.
The address starting with 2001:oDB8 is a private address for documentation so you will see it used in books like 192.168 in IPv4.
You can short hand IPv6 addresses by taking repeating fields and just putting a double :: which could be 2 or more same hextets in a row. You can only do this one in a IPv6 address. You can also remove leading zeros in a hextet. So the loopback address that is 0000:0000:0000:0000:0000:0000:0000:0001 can be expressed as ::1 Case is not sensitive in hexadecimal numbers.
Global unicast addresses are similar to single IPv4 addresses and all start with binary 001. This is a unique address to all devices.
There are 18 quintillion devices per subnet. IANA and the regional authorities will issue global routing prefix addresses which are the first 3 hextets or 48 bits. The next hextet (16 bits) is used fro subnets. which means you have 65,536 subnets available per network you are issued (the all zero and all ones can be used as subnets incase 65534 is not enough). The remaining 4 hextets are for the actual device number. You can subnet that by borrowing if you want, but 65,536 should take care of organizations.
The 3-1-4 rule sums up the previous paragraph. First 3 hextets are the global address, next hextet is the subnet and the last 4 are the interface id or individual number for the interface on the device.
EUI-64 or SLAAC will normally be used to bet the interface id although you could still use DHCP. What it does is it takes the MAC address of the interface, then puts FF FE in the middle (so if you see FF FE in the middle of the last 4 hextets you know it was an address generated from the MAC address) and flips the 7th bit in the MAC address (that is binary digit). When the machine comes on line with no address it will create that address, broadcast to make sure no one is using (if rest use EUI-64 they should not as MAC is unique) and if no response (similar to in process of DHCP getting an address) it will begin using. You can also do static addresses and use actual DHCP.
If you see things referring to the link address that is the network address.
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