maximum number of IP addresses

[logistic_guy]

What is the maximum number of IP addresses that can be assigned to hosts on a local subnet that uses the \(\displaystyle 255.255.255.224\) subnet mask?

A. \(\displaystyle 14\)
B. \(\displaystyle 15\)
C. \(\displaystyle 16\)
D. \(\displaystyle 30\)
E. \(\displaystyle 31\)
F. \(\displaystyle 62\)

 

[khansaheb]

What is the maximum number of IP addresses that can be assigned to hosts on a local subnet that uses the \(\displaystyle 255.255.255.224\) subnet mask?

A. \(\displaystyle 14\)
B. \(\displaystyle 15\)
C. \(\displaystyle 16\)
D. \(\displaystyle 30\)
E. \(\displaystyle 31\)
F. \(\displaystyle 62\)

show us your effort/s to solve this problem.

 

[logistic_guy]

show us your effort/s to solve this problem.

One of the subnetting formulas that I have given you before was:

\(\displaystyle 2^y - 2\)

where \(\displaystyle y\) is the number of zeros in the interesting octet.

That formula gives you the maximum number of host \(\displaystyle \text{IP}\) addresses in a local subnet.

Ask yourself, which octet is the interesting octet? It's obviously the fourth one!

So,

\(\displaystyle 224 = 11100000\)

We have \(\displaystyle y = 5\), therefore, \(\displaystyle 2^5 - 2 = 32 - 2 = 30\)

And the answer is \(\displaystyle \text{D}\).