[SOLVED] What does having a larger network size do?

[woofer300]

Hello! Sorry if my question does not make much sense. I am trying to understand what having a larger or smaller network size means (like a network with a subnet mask of 255.255.0.0 vs a network with a subnet mask of 255.255.255.0). Don't networks only have one public IP address? Thanks in advance, please let me know if I should clarify what I mean for anything.

 

[kanewolf]

Hello! Sorry if my question does not make much sense. I am trying to understand what having a larger or smaller network size means (like a network with a subnet mask of 255.255.0.0 vs a network with a subnet mask of 255.255.255.0). Don't networks only have one public IP address? Thanks in advance, please let me know if I should clarify what I mean for anything.

How many devices are we talking about on this network? The usual reason for having a mask other than 255.255.255.0 is to have more than 255 devices on the network. Think about a large event. There are 1500 people with phones trying to use the WIFI. The DHCP server has to be setup to allow 2048 devices to get IP addresses. The mask is then set to allow that larger pool of IP addresses.
A more restrictive subnet mask is used to more efficiently allocate IP addresses. If you only need to be able to directly access 6 devices, you can set the subnet mask to only allow that. Then the owner of the limited IP space can sell the next 7 addresses to someone else.
This calculator is pretty good for showing what IP addresses are in a mask -- https://www.subnet-calculator.com/

 

[woofer300]

How many devices are we talking about on this network? The usual reason for having a mask other than 255.255.255.0 is to have more than 255 devices on the network. Think about a large event. There are 1500 people with phones trying to use the WIFI. The DHCP server has to be setup to allow 2048 devices to get IP addresses. The mask is then set to allow that larger pool of IP addresses.
A more restrictive subnet mask is used to more efficiently allocate IP addresses. If you only need to be able to directly access 6 devices, you can set the subnet mask to only allow that. Then the owner of the limited IP space can sell the next 7 addresses to someone else.
This calculator is pretty good for showing what IP addresses are in a mask -- https://www.subnet-calculator.com/

That makes sense. Could you explain the benefit of having a smaller network, say, one supporting up to 255 devices, versus one supporting more? Specifically, what does more having more efficient allocation of private IP addresses mean, and what are the benefits of it? Thanks!

 

[bill001g]

This was mostly a design thing based on limitations on equipment that was around when networking was very new.

Devices on the same subnet will use broadcast messages for some function. These broadcast messages do not pass between subnets but they are sent to every device on the subnet. Because this causes the machines to have to take time to look at all this data that in many cases is just discarded it could degrade the performance of machines on the network. This is not true as much with modern equipment since a lot of this function has been offloaded to other chips so it has almost no impact on the cpu.

There were also non IP protocols that were used that could not pass between subnets that are pretty much no longer used.

The way subnet masks were designed was also to reduce the amount of memory and processing done by routers on the internet. In that case they wanted the networks summarized to so they used the most device in a subnet possible. To some extent this is still true but routers tend to not have issue holding a huge number of subnet prefixes.

For private subnets it really doesn't matter anymore, you mostly choose it for things that are not technically a requirement it is how you prefer to do it.
On public ip address ranges the primary concern is fully utilizing as many as possible without waste more than other considerations.

 

[woofer300]

This was mostly a design thing based on limitations on equipment that was around when networking was very new.

Devices on the same subnet will use broadcast messages for some function. These broadcast messages do not pass between subnets but they are sent to every device on the subnet. Because this causes the machines to have to take time to look at all this data that in many cases is just discarded it could degrade the performance of machines on the network. This is not true as much with modern equipment since a lot of this function has been offloaded to other chips so it has almost no impact on the cpu.

There were also non IP protocols that were used that could not pass between subnets that are pretty much no longer used.

The way subnet masks were designed was also to reduce the amount of memory and processing done by routers on the internet. In that case they wanted the networks summarized to so they used the most device in a subnet possible. To some extent this is still true but routers tend to not have issue holding a huge number of subnet prefixes.

For private subnets it really doesn't matter anymore, you mostly choose it for things that are not technically a requirement it is how you prefer to do it.
On public ip address ranges the primary concern is fully utilizing as many as possible without waste more than other considerations.

Wait, who would be reserving ranges of IPs, like more one IP? And for what purpose, since you can have so many devices on one network? Thanks!

 

[bill001g]

You are thinking too much like a home user. There are many server application that have blocks of IP addresses used by things like load balancers, These allow servers to do things like dynamically increase and decrease the number of virtual images.

Then again even for home users you might want to reserve blocks of IP for say your security cameras to keep them separate from your regular devices.