Understanding Ip Addressing
Ip addresses consist of two parts, Network and Host part. Take for example the Ip address 172.16.1.1
What is the Network part and what is the Host part of an Ip address?
You can’t tell before assigning a subnet mask for the specific Ip address. By using a subnet mask we can distinguish the network and the host portion of the Ip address. The 255 part of the mask shows the network and the 0 part shows the host.
When we are given an Ip address and a subnet mask, we can discover the network address, the broadcast address, the first valid host Ip address and the last valid host Ip address of our network.
To find the network address, when we are given an Ip and a subnet mask, the rule is simple:
- Put the Ip address and the subnet mask one on top of the other like the example below
- When the subnet mask has 255, we keep the value of the ip address unchanged
- When we see 0s in subnet mask we change the number of the ip to 0s
To find the broadcast address:
- Put the ip address and the subnet mask one on top of the other like the example below
- When the subnet mask has 255, we keep the ip address unchanged
- When we see 0s in subnet mask we change the number of the ip to 255
To find the first valid host Ip address:
- Take the network address and add 1
For example if the network address is 172.16.0.0 + 1 = 172.16.0.1
To find the last valid host Ip address:
- Take the broadcast address and subtract 1
For example if the broadcast ip address is 172.16.255.255 - 1 = 172.16.255.254
It is important but at the same time easy to be able to distinguish and tell what Ip address belongs to what network or what is the broadcast address of a network. You will find that information useful when you try to install one or even when you want to take some networks exam. Till our next article, stay Netralized! 
found it useful.. thank you
Good job man.!
But….please if you can clear this..
You begin saying…. that you can’t tell in which network an ip address belongs before assigning a subnet mask for the specific Ip address. I thought that when someone gives us an Ip address only,without a subnet mask we can use the default subnet mask.
Also I would like to see an examble subnetting a C class address whitch is I beleive more tricky. For examble 192.168.5.33/27
until next time.!
Dear Lebyathan,
I totally agree with you and as you can see in the example I use a class B ip address with the default subnet mask.
In my article I try to emphasize to the point that we can’t have an ip unaccompanied. The ip always comes with a mask. You are right saying that if they give us an ip without a mask we put the default, that’s why I wrote an article about classes of ip address.
Thanks a lot for you feedback.
I have schedule to write an article with your example ip address and subnet mask. In this future article I will give tips about how to find the network address, broadcast address, number of hosts and number of subnets.
Jim Skenderlis
[…] Lebyathans comment in the article “understanding ip addressing“, I have decided to give you an example of subnetting using the ip and subnet mask he mentioned. In […]