Subnetting Exercise
In one of the last blog we looked into an analogy of how a device in a network is by comparing the device to house in a housing community. We saw that some details on the address of a house are going to tell you which community house belongs to; example 1122, ABC Community, North Street, Castro Valley,CA-94087; tells us that house 1122 is part of ABC Community. Likewise IP address in combination to subnet mask is going to tell you which network the IP belongs to.
In this blog we will go through some exercise on how to identify the network when we get the IP address and Subnet Mask. We will also find out the range of IP address in the network, broadcast address and so on.
Let us start with a random IP address and mask 172.16.19.23/24
1. Find the network side and host side
For the IP Address 172.16.19.23/24 there are two parts, one is the network part and another is the host part. To find the network and host side of the IP address we should have a closer look at the mask in this case /24. In the blog subnet-mask-what-is-it-and-what-is-it-used-for we already talked about 3 different formats of subnet mask and how to convert between each of the network mask. /24 means there is 24 bits that is representing network of the IP address 172.16.19.23.
So in this simple step #1 we identified “172.16.19.” is the network side and “.13” is the host side.
2. Find the network ID by making all of the host bits to zero
To find the network ID after step #1 is very simple. Just make all the host bits to zero and now you get the network ID. In our example the network ID is going to be : -172.16.19.0/24 by making the last octet bits to zero. The network part is never going to change and in this example it is going to remain the same “172.16.19” and the host part will be different for different devices. In our example “.13” represents one of the device in the network “172.16.19.0/24”
3.Find the broadcast ID for the network
If network ID is derived by making all the host bit to zero, the broadcast ID is got by making all bits in the host bits to 1. So in our example the broadcast ID is 172.16.19.255 (when all 8 bits for host is 1 then it is going to be 255).
Broadcast ID is a special IP in the network which is used to reach all the devices in the network.
4. Find the IP range that can be used in the network
To find the IP address range once you finish step #3, is just to find all the numbers possible for the host side which is between the network ID and broadcast ID. So it will be starting from 172.16.19.1 to 172.16.19.254
