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This is a very good question. If you like to memorize the table instead of working the problem out to get the answer then just look at the /21 (table). If you want to understand the concept how to solve the problem mathematically then convert the 3rd octet/byte to binary and see how many bits you are borrowing to make 21 bits. Doing this will give you the insight how IP address works.
While the driver test measures you skill behind the wheel, <p>
it's important to remember that the test <p>
From there you can calculate the hosts per subnet and add them up.
actually begins before you start your engine. <p>
A pretest must be succefully completed <p>
/21 means 8 class c's equivalency. 8x256=2048 hosts or ip addreses.
before the driver can enter the open road. <p>
If the isn't in proper working order <p>
There are 32 bits total for IPv4.
or the driver fails to have proper paperwork, <p>
the test is over. <p>
This 32 bits splitted/divided into 4 octets/bytes and each octet equals 8 bits.
Here's what a pre-test looks like. <p>
Hi there. <p>
Each octe/byte can be written in decimal format so we can read. It can be set from zero to 255.
Hi. <p>
I'm Examiner Glenn.I'll be conducting your test today. <p>
So, we can use the following formula to calculate the number of subnets and hosts:
How are you doing? <p>
Fine, thank you. <p>
128 64 32 16 8 4 2 1 --decimal and can sum up to 255
Good. May I see your appointment slip, your ID and your insurance, please. <p>
0 0 0 0 0 1 1 1
That's my appointment slip … my ID and my proof of insurance. <p>
Thank you. <p>
Take 24 bits-toal of 3 octets and subtract 3 bits. This will give you the /21.
Okay, I see that you do have a valid insurance card for this car. <p>
You can go ahead and put those away now. <p>
To calculate out how many subnets within this /21, you should use 2^n=2^3=8 subnets.
Thank you. <p>
Is the engine shut off? <p>
To find out the number of IP addresses from these subnets: 8 subnets x 256 =2048 addresses.
It is. <p>
Very good. How about your parking brake? <p>
Just to remind all that this Saturday we will discuss about ACL and wild card mask.
Could you release that and reset it, please? <p>
Okay, the next thing I'd like you to do is <p>
Zero's-mean "Do Care"
demonstrade your hand signal, please. <p>
First, I'd like you to demonstrate to slowing or stopping. <p>
One's mean "Don't Care"
Now, second, right turn. <p>
And left turn, thank you. <p>
Next, I'd you to demonstrate your ability <p>
Look at Decimal:
to stop the vehicle. <p>
Okay. <p>
1 means two
Please your foot over the gas pedal. <p>
3 means four
Don't press it, but when I say, "Stop" <p>
7 means eight
step on the brake as fast as you can. <p>
15 means sixteen
Okay. <p>
31 means 32
Stop. Very good. <p>
63 means 64
Next, I'd like you to start the vehicle. <p>
127 means 128
Now, keep your foot on the brake pedal. <p>
Push the brake. Keep your foot on the brake. <p>
example:
I see the left one is good. The right one's good. <p>
router ospf 1 (how to enable ospf in global configuration mode)
And the center one's good. <p>
network 192.168.0.0 0.0.255.255 area 0
Next, we're going to check your electric turn signals. <p>
First left. <p>
This meant that the first two octets must match. The last two bytes are don't care.
Thank you. And right. <p>
And the tabs are good. <p>
example 2:
Okay, right turn signal. <p>
router eigrp 100
Left turn signal. <p>
network 172.16.254.1 0.0.0.0
Good, we're ready to go. <p>
Having arrived with the correct documents, <p>
This meant only one address/host is matched.
an understanding of hand signals <p>
and a car in proper working order, <p>
example 3:
this driver has successfully completed the pre-test <p>
router ospf 2
and moves on to the open road for the next phrase <p>
network 172.27.3.0 0.0.0.255 area 100
of her driver test. <p>
<br>
This meant the first three octets must match. The last byte is don't care.
In this video we're going to demonstrate <p>
the backing maneuver. <p>
example 4:
Back you vehicle around the corner <p>
router ospf 1
staying as close to the curb as you can. <p>
network 192.168.0.0 0.0.3.255 area 100
Then, safely continue backing in a straight line <p>
until directed to stop. <p>
This meant that the first 3 octets must match. The 3rd octet is only matched from 0 to 3. Everything else beside 0-3 is don't care. The last octet is don't care.
Thic test measure skills needed for <p>
backing out of a driveway or alley. <p>
It requires proper vision tecniques; <p>
For ACL:
primarily, looking out the back window when backing. <p>
You want to look where you driving, <p>
example:
not just in the mirror or to the front. <p>
Access-list 100 permit TCP host 172.16.1.1 host 192.168.3.2 eq 23
Remember to stop before the crosswalk area. <p>
Making sure that there aren't any pedestrians <p>
This meant Extended access-list because it filters based on source, destination, protocol, and port number.
or other traffic in that zone. <p>
You can use access-list 100 permit TCP 172.16.1.1 0.0.0.0 192.168.3.2 0.0.0.0 eq 23. For this sample evrything must match. Instead of using the word host you can specify it with 0.0.0.0.
Once you know the area is clear, <p>
continue backing. <p>
example 2:
Troungout the backing manuever, <p>
Access-list 102 permit udp 204.59.4.0 0.0.3.255 202.4.7.0 0.0.0.255 eq 53
stay witin 18-inches of the curb. <p>
That will help you stay out of the way of other traffic. <p>
Being around of what's going on around you <p>
on all directions is extremly important. <p>
Just like a quarterback with great field vision, <p>
you want to be aware of everything that's going on <p>
all around you. <p>
The difference, of course, is that driving <p>
is not a game. <p>
A single mistake made behind the wheel <p>
can be deadly. <p>
It really can't be stressed enough. <p>
When you're moving backwards, <p>
You want to be looking backwards, too. <p>
Making sure that nothing <p>
and no one is in you way. <p>
Once you've come to a stop, <p>
you ca prepaire to re-enter the roadway. <p>
Check your side view mirror <p>
and turn to look behind you <p>
so that you can see if there's any oncoming <p>
traffic approaching from behind. <p>
Once the way is clear, <p>
you can safe pull forward and onto the street. <p>
Make it a point to follow the proper steps <p>
of doing the backing maneuver <p>
and they'll become habit forming. <p>
That will make you a better driver <p>
and will help keep you and those around you safe. <p>
<br>
When driving, it's crucial to always be aware <p>
of what's going on around you <p>
in every direction. <p>
And that's certainly true when parallel parking. <p>
Do you see the brown car parked up ahead? <p>
Yes. <p>
Imagine another vehicle parked <p>
one-and-a-half car lengths behind it. <p>
Parallel between the tow vehicles. <p>
The driver pulls along side the SUV <p>
she'll park behind. <p>
Then, executes three moves as she backs up. <p>
She begins by turning the steering wheel <p>
to the right. <p>
Then back to the left to straighten-out the car <p>
and pull-up evenly along side the curb. <p>
Next, she pulls forward and parks. <p>
It only takes her three moves to park, <p>
limiting the potential impact on other drivers. <p>
Here, the driver has pulled up alongside <p>
the SUV, once again. <p>
Btu before backing up, <p>
shee sees a car approaching form behind. <p>
She waits for it to pass, <p>
then begin to parallel park. <p>
Notice that she's not just looking at her mirrors. <p>
She's turned, looking directly into <p>
her direction of travel. <p>
To be parked legally, <p>
she needs to have both right tires <p>
within twelve inches of the curb. <p>
Parking further away from the curb <p>
presens a traffic hazzard. <p>
But you careful not to run your tires up <p>
into the curb, either. <p>
That can damage them. <p>
Once you've safely parked, <p>
the drive test continues. <p>
Re-enter traffic. <p>
After all, you'll need to safely drive away <p>
fron that parking spot. <p>
Notice that our driver looks out her window <p>
before re-entering. <p>
Then, as she begins to re-enter, <p>
she looks a second time <p>
make king sure there's no traffic <p>
coming up from behind. <p>
She's successfully completed <p>
the parallel parking test <p>
and back on the road <p>
of her driver test. <p>
<br>
On the road, every move a driver makes <p>
or doesn't make <p>
can significantly impact <p>
any one in the area. <p>
A lane change or turn <p>
might seem simple <p>
But when drivers aren't aware <p>
of what's going on <p>
all around their car, <p>
the result can be catastrophic. <p>
At the next corner, turn right. <p>
Before turning, look twice <p>
and make sure the way is clear. <p>
Turn into the near lane, <p>
being careful not to swing wide <p>
as that can impact other drivers. <p>
When safe to do so, move to the left lane. <p>
When changing lanes, <p>
it's extremely important <p>
to check your mirror <p>
and look directly into your blind spots. <p>
When safe to do so, move to the right lane. <p>
You want to make distinct head checks, <p>
not just casual glances. <p>
This way, you know the path is clear <p>
before you begin to change lanes. <p>
After all, the last thing you want to đo <p>
in moving to the path of an unexpected <p>
car, van, bus <p>
or semi. <p>
Bottom line whether your turning, <p>
changing lanes or starting or stopping your car <p>
you need to be aware of everything. <p>
You might think of these areas as zones. <p>
The areas in front, behind <p>
and on both sides of you. <p>
Be aware of what's happening <p>
in the zones at all times <p>
and you'll be a better driver. <p>
<br>
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