How to calculate Wildcard Masking?

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Transcript

All right, welcome back. Now we're going to learn or we're going to learn how to calculate walk or mass. Pay close attention. close attention. I'll show you two methods. One is going to be a constant.

What is the constant number that we're going to use? Always to subtract from, right? What are we subtracting our mask, we're gonna have a constant number. And we're gonna have put our mask underneath. And we're gonna subtract it when we get our Walker mask, and annoying to you. broadcast address is your wildcard mask.

What does that mean? You know, when we did that magical line, and we use that the bid values to the right on that line, and we said, Oh, this is the you know, if it's the 16th, the 15 over here. Well, that 15 is your wildcard mask. about that. Okay, but hey, um, not going to say anything anymore. Let's go inside the lab.

All right, welcome everyone inside the wildcard masking. Wow. This is so simple. It's not even funny. So I was gonna show you two methods and I am. Okay.

So, first method, we're going to use the most simplest method whatsoever. Whatever mass they give you, it doesn't matter. We're going to use a constant number. I, this is what's called a constant. This is where you're going to use the what the mask against. Alright, let's say they give you 25525255.

We'll start off easy. dot zero. All right, this is your mask your mask that they gave you. Okay? So what you're going to do is, you're going to subtract, subtract, Okay, I'm gonna put it here, subtract. So to the five minus five is zero to divine, minus one.

Five, zero to five minutes 55 to zero, and then zero. Okay, and then this is your wildcard mask. Oh my god, that was difficult. What does that mean? It means match exactly. whatever's in that Arctic match exactly whatever is in that octet, match exactly whatever is in that octet.

And any number that comes out to that, and you know, for one through 24, okay, that's what that means. Let's use another example. Same using the same constant. Okay? How simple is that? 255 255-225-5255.

Again, this is a constant number. Alright. 255255. Let's go here. Let's do 240 dot zero. And this is your mask.

Aren't you ready? All right, and then That's for the line. And then we will subtract. Okay, well that's 00 15 to be divine, there's a wildcard mask. Oh, wow. There's welcome as a means, hey, match match.

And then here, you're saying, okay, is from a certain range, correct? Because your your incoming is 16. Okay, so we'll go from 16 dot one to M 31 dot two all 254. So it's a range now of addresses that you're permitting, deny a lot, whatever. Okay? But this is because you're you want to see shortly how they're used in access list or in Nat configurations, okay?

But that's what way of doing it doesn't matter. Just put your constant number and put the mask underneath. That's it and just subtract. Now the other method, you've seen it already, believe it or not, right? I gave you a, I stole money problem, right? Let's just make one up here, x dot x whoops, let's get some space here.

So x dot x, right, and as you do in the third octet, make that make life easy. All right, and then we're going to do 123. Line 12345. So for whatever reason, you knew you had to you need three bits, your line is there. Okay. Well guess what this x represents.

I'm gonna put it up here. This x represents 000. And these three bits this is I mean, I mean are these three bits this right here? What is that? If you have what is this here, there's 128 6432. So this the some of this is your welcome mat.

So the number that we've been using to calculate broadcast is your wildcard mask. How about that? Is the same thing if we were to do it in a class B, and we'll do it right up here to right next to this one, so we'll do a x dot x dot 1234 line and then 1234 dot 12341234. So okay, so the access means zero correct match exactly. match exactly match exactly. Oh, okay.

This is 15. right because that for this guy right here is 16. So there's one last 15 or if you want add this up is 15. And then if you add this up is 255. Move on. Well, there you go. That's your walk our mass, two ways of doing it.

You're already doing it one way. That's why I told you once you draw that magical line, you got the answers to everything. So you got two ways of creating a wildcard mask or finding out the calculation for a wildcard mask. Because everything is based on the master they give you what do you think this mask is right here? Okay, let me let me forget is not all this mask here. three bits and you got 816 24 plus three is a cider 27.

And what is this mask right here? 816 plus four is 20. So this is a cider 20. Okay, and then well does this is representing decimal numbering to drive to define 240 dot zero. What does this represent and that decimal format 25 dot 255 dot 255 dot 224. Okay, this is why I kept on I keep telling you That learning that bits of decimal table okay?

Learning how to convert from one to the other is extremely important because once you draw that line you know how to do everything, but you got to learn the bit the decimal table you got to learn the conversion and that was easy. You saw that was easy. So beautiful God gore that lecture again. All right. But this is important is is very simple, but it is important, because as you'll see next, we get into the next lecture. This is used in OSPF or wildcard masking.

I'll see you next

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