Why subnet mask is necessary

For example, if a server has an IP address of You need to create 5 sub networks each network has a maximum of 10 hosts. We can only use the first 8 bits for out subnets as these 8 bits have been allocated as host addresses. So Subnet masks of Your email address will not be published.

Save my name, email, and website in this browser for the next time I comment. Skip to content Why are subnet masks necessary? What is subnet mask example? What does the subnet mask Is subnet mask always ? What is default subnet mask? Can two computers with different subnet masks communicate? What is the difference between a subnet and a VLAN? Can I change my subnet mask?

What is difference between VPC and subnet? What is a What destination adress is What is difference between default subnet mask and custom subnet mask? To assign an IP address to a network interface since the advent of CIDR, there are two parameters: a subnet mask and the address. Some know how to calculate subnet masks by hand, but most use subnet mask calculators.

There are several types of network subnet calculators. Some cover a wider range of functions and have greater scope, while others have specific utilities. These tools may provide information such as IP range, IP address, subnet mask, and network address. In this situation, the IP address is followed by the number of bits in the mask. For example:. Blog Contact Support. Request a Demo. Subnet Mask Definition Every device has an IP address with two pieces: the client or host address and the server or network address.

IP Address Classes and Subnet Masks Since the internet must accommodate networks of all sizes, an addressing scheme for a range of networks exists based on how the octets in an IP address are broken down. How Does Subnetting Work? The cookie is used to store the user consent for the cookies in the category "Performance". It does not store any personal data. Functional Functional.

Functional cookies help to perform certain functionalities like sharing the content of the website on social media platforms, collect feedbacks, and other third-party features. Performance Performance. Performance cookies are used to understand and analyze the key performance indexes of the website which helps in delivering a better user experience for the visitors.

Analytics Analytics. Analytical cookies are used to understand how visitors interact with the website. These cookies help provide information on metrics the number of visitors, bounce rate, traffic source, etc. Advertisement Advertisement. Advertisement cookies are used to provide visitors with relevant ads and marketing campaigns. These cookies track visitors across websites and collect information to provide customized ads. Others Others. Other uncategorized cookies are those that are being analyzed and have not been classified into a category as yet.

Class sizes are not the network sizes. In practical networks all IPv4 networks are broken up into subnets that are smaller than the class size. For example you could break up the class C network In reality most companies only get enough IPv4 addresses for the servers that need to be on the public Internet.

Having IP networks only in class size blocks was too restrictive in limited the number of networks that could be allowed - the class A networks taking half of the space. Not to mention that having a 24 billion node network is completely unmanageable Instead in Classless Inter-Domain Routing CIDR was introduced to allow the networks to be split up.

Also to be clear the purpose of the subnet mask is to determine which hosts are on the local network and which are outside of the network. Hosts can talk directly to hosts on the same network, but they need to communicate with a router to talk to hosts on external networks.

Right, but if someone were to subnet that network, you'd need the subnet mask to know how big a subnet you were in. Yes, with classful addressing, the class tells you the size of the network and allows you to tell whether a host is in the same network as you, but if that network is subnetted, without the subnet mask, how would you know whether another node is in the same subnet as you?

Say you're on an Ethernet network. We use classful addressing with subnetting. Your IP address is 1. Do you use ARP to reach that address? Well, it depends on whether 1. Even if they're in the same network, if there in different subnets, a router needs to be used. If they're in the same subnet, then ARP should be used.

I think you're confusing subnetting with CIDR, actually. Without CIDR, even with subnetting, you don't need the subnet mask between administrative regions. But you still need it inside the network! A subnet mask is used to do a bit wise operations on an IP address, in conjunction with a network address. If my memory serves me well, you take an IP address and do a bit wise AND on it and the subnet mask for a given network.

If the result equals the network address, then the IP address is on that particular network. Routers that have routing tables of network addresses and subnet masks can use simple binary maths which is very fast, if not the fastest for computers to handle to find out which interface to punt a packet out of. There aren't many protocols in common use today that respect this anymore see Fiasco Labs comment - RIP is the only one I can think of. So, this statement in your question:.

Routers define the edges of sub networks. Anything needing to go through a router is on a different network - and vice versa: anything needing to go to a different network needs to go through a router.

The subnet mask is how all machines can tell whether traffic is for the current network or needs to be sent to a router to get to its destination. Except for Adrian's answer I'm not sure any of these actually mention WHY we use the mask instead of some simpler to understand solution--and he only touched on the fact that masking is FAST, I mean why not just specify that you are interested in addresses You actually could now to some degree completely remove numbers from routing, most PCs could handle the kinds of traffic they are sent, but there is still a problem on the larger scale devices.

Filtering like this is happening all the time, and it's happening a LOT. For a solution that is so easy on the hardware it is also very flexible.