# [SOLVED]Wild card mask and Finding ranges

#### Alumejr

##### Commendable
I was practicing on some questions in preparation for the ICND1 and the question is about wildcard mask and ranges.

Which Address and wildcard mask combination will match all IPv4 addresses in the networks 172.30.0.0/24 through 172.30.15.0/24
A. 172.30.0.0 0.0.1.255
B. 172.30.0.0 0.0.31.255
C. 172.30.0.0 0.0.15.255
D. 172.30.0.0 0.0.3.255
E. 172.30.0.0 0.0.63.255
F. 172.30.0.0 0.0.7.255

The answer is C something i found by running the question on an online subnetting calculator. Came out with the subnet mask of 255.255.240.0

Now i do understand that to get the wild card mask you do 255.255.255.255 - 255.255.240.0 and that is how you come up with 0.0.15.255
Now my question is from the question how did you come up with that answer.

#### bill001g

##### Titan
Not sure that is a pretty basic question of what range of IP are covered by a subnet mask. The bottom being 0.0 and the top being 15.255

Maybe some things to think about would be why is it the same answer for 172.30.32.0/24 to 172.30.47.0/24 except the ip address would not be 172.30.0.0

And why would the answer be "B" if the final ip on the question way 172.30.16.0/24. A question like this is much more likely on the ICND tests they like to things on there to try to trick you. This actually matches more than just that list but there is no other way to do it with a single statement.

#### bill001g

##### Titan
Not sure that is a pretty basic question of what range of IP are covered by a subnet mask. The bottom being 0.0 and the top being 15.255

Maybe some things to think about would be why is it the same answer for 172.30.32.0/24 to 172.30.47.0/24 except the ip address would not be 172.30.0.0

And why would the answer be "B" if the final ip on the question way 172.30.16.0/24. A question like this is much more likely on the ICND tests they like to things on there to try to trick you. This actually matches more than just that list but there is no other way to do it with a single statement.