In this section of campus network design and operations we're going to be talking about IP adressing. What are IP addresses? Internet connected networks use two type of IP addressing. IPv4, which is very common these days and is now considered legacy internet protocol. Remember that we're running out of IPv4 addressing. So the new internet protocol that is being pushed is now IPv6. This presentation describes IPv4 addresses and IPv6 addresses and addressing. In general the campus network design workshop uses both IPv4 and IPv6 for all exercises. This means we're using dual stack networks and we have both protocols running in parallel. What is an IPv4 address? An IPv4 address is a 32-bit binary number. When we talk about binary numbers remember we mean all ones and zeros. So if you have a 32-bit binary number how many unique addresses would you have in total? For those of you that are not very good in binary mathematics we'll just show you. You will have two to the power of 32 unique addresses which is more than 4 billion 200 million addresses. IPv4 addresses are conventionally represented as four dotted decimal octets. If you turn on all the bits you will have 32 ones which is also represented in decimal by 255.255.255.255. Remember we said at the beginning that IPv4 addresses are represented as four dotted decimal octets. We do this so that we can remember IPv4 addresses easily. If we were to remember IPv4 addresses using binary it would be almost impossible for us to remember. So can you explain why you have one one one one one eight ones equal to 255 in decimal? Remember we're talking about binary mathematics so each bit is basically to the power of two. The first bit is two to the power zero. The second bit is two to the power of one. This is from the right and so on to the eighth width which is two to the power of seven. If you do binary mathematics it means that one one one one one one one, this is eight ones in binary, is the same as two to the power of zero times one plus two to the power 1 times 1 plus 2 to the power of 2 times 1 plus 2 to the power of 3 times 1 plus 2 to the power of 4 times 1 plus 3 to the power of 5 times 1 plus 2 to the power of 6 times 1 and 2 to the power 7 times 1. If you expand that you're going to have 1 plus 2 plus 4 plus 8 plus 16 plus 32 plus 64 plus 128 which will give you 255. As you can see on the screen each which corresponds to a power of two as indicated. We're going to show you an another example of an IPv4 address. As you can see on the screen the IPv4 address is 220.127.116.11 Please remember that IPv4 addresses are represented as 4 decimal octets. If you were to remember the binary digits as i said previously it would be almost impossible in this case. The ip address 18.104.22.168 is represented by the binary digits shown on the screen. Can you explain why zero zero zero one zero zero one one is ninety? Okay, we'll show you on the next slide how we arrive to that conclusion. Remember with binary mathematics each digit is to the power of two. As you can see on the screen zero zero zero one zero zero one one has eight bits so the first bit is going to be two to the power zero. This is the one on the right is the least significant bit followed by the second digit as we had shown you previously the second bit is also one which is also two to the power of one, the third and fourth bits are zero the fifth bit is one in this case it's two to the power of four the sixth seventh and eight bits are zero in this case. So if you were to convert this to decimal you would have two to the power of zero times one plus two to the power of one times one plus two to the power of two times zero plus two to the power of three times zero plus two to the power of four times one plus two to the power five times zero plus two to the power of six times zero plus two to the power of seven times zero. If you tabulated this you would have it being one plus two plus zero plus zero plus sixteen plus zero plus zero plus zero which is equal to nineteen. Remember only the bits that are 1 are going to be converted to the decimal number. Otherwise 2 to the power of anything times 0 is also 0. So that's why you arrived at 19.
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