So we talked about what our I P addresses are and
how they're composed using our bits of information. And we mentioned a little bit about our I P address is having a network I d and the host city network, part of our I P address and a host part of I p r i P. Address.
Well, when we're encountering a situation where we're on our computer and we just look at our i p address, how do we know which part is our network idea in which heart is our host city? That can be
fairly significant if we're trying to make sure we're tryingto look at another computer and see if their I P addresses on the same network is ours, or we're trying to increment ourself up to the next address that's available in our range.
we have something implemented called a sub net mask. Now, this sub net mask
is you can think of it as a filter that we put on top of our I P address, and it lets us know which portion of that I P address is. Our network I d. And which portion of our I P addresses our host, Saidi.
So let's take a look at that. So we have our I P address here 1 92.1 68.1 dot one. When you look in a sub net mask,
some of our more common sub net masks will look something a bit like this to 55.2 55 to 55 0 What does that mean? What we're about to talk about is just going to be some very basic level sub net
masking. There's a lot more complicated ways where you could do something called sub netting and cider insider calculations where you can change these numbers dramatically and create additional networks if you need them. But
that'll probably be something that gets into a little bit more advanced than a little bit more on the network plus side. So for a plus side, we're just gonna talk about some basics sub net masking.
Now our network idea again basically asks, That's the question. What neighborhood? In my end, what street am I on?
Where is our host? I d asks us, tells us. Who am I? Which house am I on this street?
So we have our sub net mask over i. R I P address,
you'll often see this. If you're looking in your I p configuration, it'll say I p a p b for dress and sub net mask.
So are simple way to do this in a situation where our sub net mask looks like 20 to 55 to 55 to 55 0
is simply to take each segment that has that 2 55
covering it. So are for both of our first segments.
means that these this string of our numbers here is our network segment.
So we can say that this is our network segment and this is our host segment. Let's take a look and let's use a different I p address just to make sure we got it down. Let's change your I P address and let's have 10.0 dot 0.1,
and let's say our I P address is going to be 2 55 to 55 0.0. The reason we used to 55 again is because that's the highest number we can have
behind each of our dots. If you see an I. P, you see something that's straight to 55. That's typically a broadcast to all the I P addresses it can reach. So our highest number
before each of these dots is in each of our octet, says 2 55
So with this number, we have 2 55 1st segment
2 55 in our second segment,
between that 2 55 and that zero.
network, and this will be our host. We can see how that gets a little
a little bit easier to understand, especially with this simple are simple sub nets of 2 55 to 55 0.0 or using our 2 55 sub nets
when we're talking about are different. Sub nets are
sub net Mask really comes in handy because when we have different networks, say when we have
r Tenn 0.0 dot zero that one
let's go ahead and throw in another address, 10.0 dot to 0.0 and 10.1 dot 0.3. We need to figure out which of these addresses are on the same network in which of them are different on different network.
This is especially important because
I P addresses that are on different networks need to have their information routed through a router
before they can communicate. So when you hear about having a router in an office or a router in your home,
all the computers that are on one side of that router have to have the same network I d portion. They have to be on the same network.
And if they want to communicate any computers that have I P addresses set on a different network, then they have to go through a router to communicate this.
This has to deal more with our network plus side as to how this all goes on and why this happens. But we do want to just know that any computers that are on the same network I d, can talk to each other without a router. In any computers that are on a different network idea, different network than us have to talk through a router before they can communicate properly.
So when we look at all of these
three i p addresses will say that for all three I p addresses are sub net mask
2 55.2 55.0 dot zero.
So that means our 1st 2 octet it's
in All three of these I p addresses are going to be our network I d.
And then our second to ox. It's our last two AQ debts are going to be our hosts, I d.
So it can very quickly see that. Okay, Our network i d For our first and second i p address, they're on the same network because this identical tin 0.0 in 10.0 both of these were on the same network,
so they can talk without a router.
But when we look at this address here
this is on its own network. This is over by itself. So these two want to talk.
If these two wanna talk,
If this one wanted wants to talk to these any either of these two,
this one's got to go through a router or they've got to go through a router to get to it.
So our i p addresses are sub net mass. You'll see as to 35 to 55 dot which zero another 2 55
And that's how we identify them. In our of our simplest sub net masks, you may see a sub net mass expressed is what's called cider notation. This is a little bit more complicated. We have cider Address C I. D R. Which stands for class, is introducing routing around address,
and you'll see this as a slash
we talked about how we have our different ock tests. You probably won't see slash four, but
more commonly you see things such as slash eight sash 12. These air also ways that sub net masks are expressed. When we're talking about it's slash eight.
We're counting backwards on our
I P address. Remember, our I P address is just one long string of four
octet. It's so it's 32
bits and eyes, 32 bits either one's or zeroes arranged at each interval of eight. There's a dot so we have and then a period, and then we have that four more times. So we have 32 bits. Well our cider notation our Dash 8-12.
That's going to be how many from the
reading backwards from
How far? Submit Masco CE. Let's use a little example to help. It will be a little bit more easily understood. Let's use our famous example again. 1 92.1 68.1 dot one. Let's take a look at that and say We see a satyr notation which says
What does that tell us? Well, that tells us that
the last eight bits of this address
Now this doesn't make much sense when we look at it like this because we say, Well,
Well, in this case, it does work, but, um, we have to expand that out.
Say, 00100112345678 That doesn't work.
That's not our split. There
Dash eight is again talking about when we translate this back into the binary zeroes and ones are last eight bits of this
because, remember, we have eight
eight bits in this first segment
that make up this number
eight bits. In this second segment,
again. Eight, No matter how high are number is or how low our number is, there are still eight bits of data that make up that number. They might be a zero. They might be the one. It doesn't matter, no matter how high or how low the number. Is there still eight bits of data that make that number up?
So our last eight being our host, I d.
Is this last eight bits here?
So that means our 1st 3 segments are our network I d. In our last segment is our host, I d.
If we change this to Dash 16
this they are last two octet star would be our our host i d. And our 1st 2 octet ce would be our network. I d.
In our I p address our network, I d always because becomes before our hosts I tr host idea is always going to be at the end of our network address, and our network idea is going to be at the beginning.
Cider notation is not something that you'll need to know extremely in depth
for, say, the A plus exam. But it is something to be aware of when you see that slash. Whichever that's still a sub net mask, but more commonly you'll be looking at
are 2 55 to 55 0.0. And then later on, we'll even get into some more complicated submitting, which involves additional mathematics and the deficient equations. But we'll take a look at that as the time comes. So let's cool down a little bit from our cider notation and just wrap up
with just some general rules for our sub net masks.
First of all, there's no we can't have any breaks in the middle of our sub net masks,
so we can't have 2 55.0 dot 2 55 0 That's an invalid subject mask. It's not valid because of our break here.
break at the beginning of our subject mask either.
We can't have 0.2 55.2 55.0 Because remember our network I d. Has to come before our host, I d. So this is an invalid subject mask. This is also an invalid sub net mask,
is a valid sub net mask. So just remember no breaks in the middle. No breaks the beginning and you'll have a good idea of our sub net mask. So just remember that when we're trying todo to determine our network, I d versus our host i d portion.
That's what our sub net Mass comes in handy for. And we just lay that over top of our I P address,
see where zero segments are and were able to determine our
network i d. In our study.