Subnetting class A

How do you find the subnet # and host ranges for the following?

11.220.100.18, mask 255.255.0.0

11.220.100.18, mask 255.255.128.0

What's the magic number in each case? For the first one, I think you have 254 subnets, but what about the range of each subnet?

I find these two a bit confusing.

Find more posts tagged with

Save $250 on 2025 certification boot camps from Infosec!

Book now with code EOY2025

Button

Comments

EdTheLad

binarysoul wrote:

How do you find the subnet # and host ranges for the following?

11.220.100.18, mask 255.255.0.0

11.220.100.18, mask 255.255.128.0

What's the magic number in each case? For the first one, I think you have 254 subnets, but what about the range of each subnet?

I find these two a bit confusing.

Is this what you're looking for?

11.220.100.18 /16
host range 11.220.0.1 -> 11.220.255.254

11.220.100.18 /17
host range 11.220.0.1 11.220.127.254

binarysoul

Is this what you're looking for?

11.220.100.18 /16
host range 11.220.0.1 -> 11.220.255.254

11.220.100.18 /17
host range 11.220.0.1 11.220.127.254

It's right, but which subnet each IP address belongs to? Like some, I can perfectly do subnetting with class B and C, but not as good with A.

EdTheLad

11.220.100.18 /16

If you look at it from a class point of view its class A, you have an additional 8 bits of subnetting, subnets are 11.1.x.x -> 11.255.x.x, so the address 11.220.100.18 is in subnet 11.220.0.0

11.220.100.18 255.255.128.0
You borrow 9 bits, thrid octet is 100 which is < 128 therefore its in the first
subnet, 11.220.0.0, if the address you gave was 11.220.160.16 it would be in the second subnet 11.220.128.0