How to Subnet Anything in Under 5- Minutes:


This is below table you have to memories for understanding subnetting trick.

Subnet Mask
128
192
224
240
248
252
254
Target Number
128
64
32
16
8
4
2
Bit Place
1
2
3
4
5
6
7
No. of valid Subnets
N/A
2
6
14
30
62
126




Question: We have IP address: 192.168.10.1/24 Please find the below parameter.

1. Network ID.
2. Broadcast ID
3.First Valid
4. Last valid.
5.Number of host 
6. Subnet Mask

Solution:

Default mask for Class C:  255.255.255.0



Step 1. In the bottom line (Number of Valid Subnets), move from right to left and find the closest number that is bigger than or equal to what you need:
Ex: Nine subnets—move to 14


Step 2. From that number i.e 14, move up to the line called Bit Place.
Above 14 is bit place 4.
Step 3. The dark line is called the high-order line. If you cross the line, you have to take reverse direction.
You were moving from right to left; now you have to move from the left to right.
Step 4. Go to the line called Target Number. Counting from the left, move over the number of spaces that the bit place number tells you.
Starting number is 128, moving 4 places takes you to 16.
Step 5. This target number is what you need to count by, starting from 0 and going until you hit 255 or greater. Stop before you get to 256:
0
16
32
48
64
80
96
112
128
144
160
176
192
208
224
240
256 Stop—too far:

Step 6. These numbers are your network numbers. Expand to finish your plan.

Network #
Range of Valid Hosts
Broadcast Number
0 (invalid)
1–14
15
16
17–30 (17 is 1 more than network #
30 is 1 less than broadcast#)
31 (1 less than next network #)
32
33–46
47
48
49–62
63
64
65–78
79
80
81–94
95
96
97–110
111
112
113–126
127
128
129–142
143
144
145–158
159
160
161–174
175
176
177–190
191
192
193–206
207
208
209–222
223
224
225–238
239
240 (notvalid)
241–254
255

You can notice that Notice that there are 14 subnets created from .16 to .224.
Step 7. Go back to the chart and look above your target number to the top line. The number above your target number is the subnet mask.
Above 16 is 240. Because We started with a Class C network, the new subnet mask is 255.255.255.240.




   

4 comments:

  1. i don't understand how you got 255.255.255.240 how did you know where to place the .240 ?

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    Replies
    1. As per the question we have IP address 192.168.10.1/24 so default mask for Class C is 255.255.255.0.We are calculating 9 subnets according to the above table.

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