Learning to subnet

[Thetech]

I've been trying to learn how to subnet but am confused by an example on a lesson page.

Here is the example:

Determine how many bits you must borrow from the hosts portion.
Use the following equation:

2n - 2 >= Number of subnets required
So if you need 25 subnets:


2n - 2 >= 25
2n - 2 >= 25
25 - 2>= 25
32 - 2 >= 25
If n = 4 then it would have been 16, less than 25.

Note: At this point, you should account for expandability, if you are going to need more than 30 (25-2 )sub-networks in the future, you should go one greater, like 62 (26-2). Remember, the more networks you have, the less collision domains you have. But you will need routers to get them to speak to each other.
--------------------------------------------

Okay I assume this is a typo because 2 to the 5th power is 64 and 2 to the 4th power would have been correct?

 

[ch33zw1z]

2^4 is 16, !=correct
2^5 is 32, so n=5

Does that help?

 

[Thetech]

Originally posted by: ch33zw1z
2^4 is 16, !=correct
2^5 is 32, so n=5

Does that help?

I'm still lost, 2 to the 5th power= 2x2x2x2x2

Therefore
2 x 2 x 2 x 2 x 2
2 4 16 32 64

Right?

 

[ch33zw1z]

2 times 2 = 4 times 2 = 8 times 2 = 16 times 2 = 32

you're messing up the math between the 4 and 16

 

[Thetech]

Originally posted by: ch33zw1z
2 times 2 = 4 times 2 = 8 times 2 = 16 times 2 = 32

you're messing up the math between the 4 and 16

Craps, I see I was doing 2 to the 6th power instead of 5

 

[Jamsan]

Originally posted by: Thetech

Originally posted by: ch33zw1z
2 times 2 = 4 times 2 = 8 times 2 = 16 times 2 = 32

you're messing up the math between the 4 and 16

Craps, I see I was doing 2 to the 6th power instead of 5

Yes, you missed 2^3 in your original calulation of:

2 x 2 x 2 x 2 x 2
2 4 16 32 64

it's 2 4 8 16 32