Subtitles of the Movie

In this module we look more closely at binary addressing. As I mentioned in the previous module all IP addresses are a 32 bit numbers. In other words this decimal of 192.168.2.100 this is what the human being would input to a computer. To the computer it looks like this. A string of 32 ones and zeros that we deal with one octet at a time and in fact I put periods in here to separate the octets but the computer doesn't really use the periods at all. We use the periods to help keep things separate. So the number 192, the decimal number 192, if you were to put it in its binary equivalent is 11 followed by 6 zeros, 16810101 3 zeros 2 is 6 zeros followed by 1 and a 0 and then 100 looks like this. If you want to quickly reference what any given decimal is in binary, you can punch it into the calculator and to open the calculator, you go to start, accessories, calculator should be there, but change from decimal to binary. So the decimal number 100 in binary looks like this, 1100100. Now notice that's only 7 numbers and in an IP address we deal with things an octet at a time. So this for example if you were to look up 2 decimal and we'll enter in the number 2, change it to binary that's what it looks like. So if were to work with it in an IP address, that number 2 will have to append with six place holders for zero. Now what does it mean when I'm talking about placeholders? This concept can help you understand binary addressing. When you're dealing with an octet and dealing with binary numbering, you're dealing with powers of 2 and the 1 or the 0 in the octet is a state of on or off. So this is the on state for the 2 to the zero placeholder which decimal is equivalent to 1, this would be on equivalent to the 2 to the first power, which is decimal 2. 2 squared if on is 4, 2 cubed if on is 8, 2 to the 4th 16, 2 to the 5th 32, 2 to the 6th 64, we're doubling each time, 2 to the 7th power if on is 128. If we were to take this entire octet of all ones and turn them all on, then we get the decimal equivalent of 128+64+32+16+8+4+2+1 that equals 255. That 255 is something that is a ceiling on an octet's decimal equivalent. You won't see a decimal equivalent higher than 255. Nor will you see a decimal lower than zero. If these were all off, these are all set to zero, then the decimal equivalent is zero. So for example what is the decimal equivalent of 10, what is the binary equivalent for the decimal of 10. This would be off, this would be off, this would off, that would be off, the 8 placeholder would be on, the 4 would be off and the 2 would be on, the 1 would be off. So in other words 8+2=the decimal of 10. And probably that's not the greatest example because it's a one zero, confused, think you're dealing with binary but this is binary, what about 12? What does 12 look like? 11 off, off, so 8+4 is 12. So this is how we deal with things in binary notation, and this becomes an important skill to have as we start to talk about IP address classes and as we start to talk about sub-netting and super netting and even CIDR notation down the line. We need to really understand what these binary equivalents are all about and how the computer looks at an IP address and not only an IP address but a subnet mask. A subnet mask is also a 32 bit address. For example the subnet mask of 255.255.255 is 24 ones followed by 8 zeros. Again notice what's significant about the subnet mask, all ones followed by all zeros. And this rule holds true no matter what subnet mask we're dealing with and as we move forward, you're going to see subnet mask that looks something like this. But that subnet mask also follows the rule of all ones followed by all zeros. So just like our IP address is a 32 bit number, our subnet mask is also a 32 bit number. The rule about subnet masks, all ones and then all zeros. That separates out which of these ones and zeros in the IP address identify the network number and which identify the host number as the computer looks at an IP address.