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In SIMPLE terms, what is a subnet?


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#1 helpmeplz2

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Posted 07 May 2012 - 03:01 AM

Please in the most dumbed down laymen simpleton way you can think to describe it. Also, what is a subnet mask? And can you please like add a diagram of it? thanks

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#2 ciderZA

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Posted 07 May 2012 - 08:15 AM

To put it simply, its a way of spitting up network into two or more networks ...

Think of it like an address.

http://en.wikipedia.org/wiki/Subnetwork

Edited by ciderZA, 07 May 2012 - 08:16 AM.


#3 helpmeplz2

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Posted 08 May 2012 - 04:24 AM

What type of network? LAN? Or what?

#4 coxchris

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Posted 08 May 2012 - 10:56 AM

any tpye of network

Three basic things to connect to internet are
IP address
Subnet Address
Gateway Address

There is three types of Classes Class A,B,C Class C is the common one

Each Class has its own sub net address

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#5 NpaMA

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Posted 08 May 2012 - 11:06 AM

It can be any type of network. "Subnetting" is dividing a default address space into separate networks. For example, 192.168.2.0 is a Class C address with the default mask 255.255.255.0. If you wanted to divide it into into 2 networks, the mask would be /25 or 255.255.255.128. This would give you the networks, 192.168.2.0 - 192.168.2.127 & 192.168.2.128 - 192.168.2.255, both with the mask 255.255.255.128.

That's what a "subnet" is. Basically dividing a major network into multiple smaller networks. There's many reasons you would want to do this with some of the most common reasons being to use the same address space behind multiple routers, keeping broadcast traffic down, and separating multiple user networks (ex: student LAN at a college vs faculty LAN).

A subnet mask is what tells the router what IP addresses are in that subnet. So when the router sees it has an IP of 192.168.2.1 and a mask of 255.255.255.128, it knows that it's on the network 192.168.2.0/25.

#6 helpmeplz2

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Posted 09 May 2012 - 08:02 PM

So is a subnet automatically created or can I make one manually myself? And I use a home wireless router, do I have a subnet?

And tell me if I have this correct:

Network > Subnetwork > Client ???

#7 helpmeplz2

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Posted 09 May 2012 - 08:03 PM

And is a subnet created by a network admin or your ISP?

#8 coxchris

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Posted 09 May 2012 - 08:53 PM

A wireless Router can automatically configure the appropriate setting If you are configuring for DHCP If you are running a static IP (fixed ip) you need to know the sub nets of that IP address

A ISP can assigned sub-nets

For Home Network you always use DHCP.

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#9 helpmeplz2

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Posted 09 May 2012 - 10:10 PM

A ISP can assigned sub-nets

Please explain. :)

#10 NpaMA

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Posted 09 May 2012 - 10:55 PM

A ISP can assigned sub-nets

Please explain. :)


Let's assume your ISP is using 192.168.16.0/24 for all the users in your area.

They have 2 users, each using 5 IPs. Instead of having all of the addresses on the same network, they can assign them blocks of IPs so that the client networks are separate, which as I mentioned above can be used for privacy/security reasons and to make the network easier to manage.

So Client 1: 192.168.16.0-192.168.16.7, Client 2: 192.168.16.8-192.168.16.15. Closest subnet you could use for 5 IPs is an 8 block, which would have the mask /29 or 255.255.255.248. (2 IP addresses in the range are reserved for the network ID and broadcast address. In this example the network ID's would be 192.168.16.0, 192.168.16.8 and the broadcast addresses would be 192.168.16.7 and 192.168.16.15).

So is a subnet automatically created or can I make one manually myself? And I use a home wireless router, do I have a subnet?

As a home user, you really do not have a need to subnet unless you want to create two separate networks. For example, if you had a local home wireless and one you left unsecured for guests/neighbors then you may want to separate the networks for security reasons. Unless you're doing something like that, subnetting your addresses would only cause problems - not to mention most consumer level routers would not support being about to forward between networks correctly.

Your ISP most likely has subnetted your public IP address, however.

Network > Subnetwork > Client ???

No. There is NO DIFFERENCE in a subnet and the main network to the end user. It's something a system admin/network admin would use to help maintain a network. "Subnetting" the network is dividing that range into separate networks as I said above.

Of course, these are just basic examples. It does get more complicated and more reasons to do it in a corporate setting or in a network that is using class A/class B ranges.

Another major benefit in subnetting networks is lets say you have the class A range of 8.0.0.0/8. That means you can have devices using 8.0.0.1 - 8.255.255.255.254. I really doubt anyone has that many devices/hosts, so thus it would be pointless for someone to be using a range that large. Now divide that range up by subnetting and assign networks for 1,000 hosts over 1000 branches/buildings, and it has a purpose and the full address space may eventually be used.

---

Basically: Subnetting helps reduce unused hosts. The reason behind subnetting in the beginning was because you had 3 choices when getting an IP range.

Class A: 16777214 hosts
Class B: 65534 hosts
Class C: 254 hosts

So a person that needed 1,000 IP addresses could not use a class C network, but when they went up to a class B they were only using 1,000 out of an available 65,534. Wasting 64,534 host IP addresses. As you can imagine, this would've made us run out of IP addresses very quickly.

#11 helpmeplz2

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Posted 09 May 2012 - 11:07 PM

Thanks for the reply. :) And this is really important I understand this.

Let's assume your ISP is using 192.168.16.0/24 for all the users in your area.

How big of an area and how is this decided?

They have 2 users, each using 5 IPs. Instead of having all of the addresses on the same network, they can assign them blocks of IPs so that the client networks are separate, which as I mentioned above can be used for privacy/security reasons and to make the network easier to manage.

So Client 1: 192.168.16.0-192.168.16.7, Client 2: 192.168.16.8-192.168.16.15. Closest subnet you could use for 5 IPs is an 8 block, which would have the mask /29 or 255.255.255.248. (2 IP addresses in the range are reserved for the network ID and broadcast address. In this example the network ID's would be 192.168.16.0, 192.168.16.8 and the broadcast addresses would be 192.168.16.7 and 192.168.16.15).

I don't really understand. :(

As a home user, you really do not have a need to subnet unless you want to create two separate networks. For example, if you had a local home wireless and one you left unsecured for guests/neighbors then you may want to separate the networks for security reasons. Unless you're doing something like that, subnetting your addresses would only cause problems - not to mention most consumer level routers would not support being about to forward between networks correctly.

Can you please give me an example of a device that could be manually subneted?

And can you please explain to me the difference behind an ISP subnet and a home/office subnet?

#12 NpaMA

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Posted 09 May 2012 - 11:24 PM

How big of an area and how is this decided?

It was just an example. That range I used would have a max of 254 users/hosts on the network. How is it decided? Well it depends on how many users need addresses in that region/area.

I don't really understand. :(

That's OK. That was actually a pretty advance subnetting breakdown, lol.

Can you please give me an example of a device that could be manually subneted?

And can you please explain to me the difference behind an ISP subnet and a home/office subnet?


Addresses are subnetting. The end user and device does not know the difference between being on the "main" network and a subnetted network. Subnetting really is just saving address space. (as I said above with the class c vs class b thing)

The difference between an ISP subnet and a home/office subnet? For the most part, a home network just uses a private (normally class C) address range similar to 192.168.2.0 - 192.168.2.255 with a subnet mask of 255.255.255.0.

Now let's assume a ISP has to use 192.168.2.0 between 3 cities. By Subnetting they could assign IP's 192.168.2.0-192.168.2.64 to City 1, 192.168.2.64-192.138.2.127 to City 2, and 192.168.2.128 - 192.168.2.255 to city 3.

As I said before, this saves address space because what if City 1 only needed 50 IP addresses? Without subnetting it down, they would've give city 1 192.168.1.0 - 192.168.1.255, wasting 204 IP addresses. Repeat using 192.168.2.0 - 192.168.2.255 for city 2, and 192.168.3.0 - 192.168.3.255 for city 3 and look at how many IP addresses you have wasted. If they confine all 3 cities into separate subnets on the 192.168.2.0-192.168.2.255 major (Class C) network, they just saved ALOT of IP addresses. THIS is the reason for subnetting because at the rate we were going, we would have easily run out of IP addresses.

Edited by NpaMA, 09 May 2012 - 11:31 PM.


#13 helpmeplz2

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Posted 09 May 2012 - 11:29 PM

How big of an area and how is this decided?

It was just an example. That range I used would have a max of 254 users/hosts on the network. How is it decided? Well it depends on how many users need addresses in that region/area.

I don't really understand. :(

That's OK. That would actually a pretty advance subnetting breakdown, lol.

Can you please give me an example of a device that could be manually subneted?

And can you please explain to me the difference behind an ISP subnet and a home/office subnet?


Addresses are subnetting. The end user and device does not know the difference between being on the "main" network and a subnetted network. Subnetting really is just saving address space. (as I said above with the class c vs class b thing)

The difference between an ISP subnet and a home/office subnet? For the most part, a home network just uses a private (normally class C) address range similar to 192.168.2.0 - 192.168.2.255 with a subnet mask of 255.255.255.0.

Now let's assume a ISP has to use 192.168.2.0 between 3 cities. By Subnetting they could assign IP's 192.168.2.0-192.168.2.64 to City 1, 192.168.2.64-192.138.2.127 to City 2, and 192.168.2.128 - 192.168.2.255 to city 3.

As I said before, this saves address space because what if City 1 only needed 50 IP addresses? Without subnetting it down, they would've give city 1 192.168.1.0 - 192.168.1.255, wasting 204 IP addresses. Repeat using 192.168.2.0 - 192.168.2.255 for city 2, and 192.168.3.0 - 192.168.3.255 for city 3 and look at how many IP addresses you have wasted. If they confine all 3 cities into separate subnets on the 192.168.2.0-192.168.2.255 major (Class C) network, they just saved ALOT of IP addresses. THIS is the reason for subnetting because at the rate we were going, we would have easily run out of IP addresses.

Alrighty I think I am starting to get it, but can you please post like a diagram of an ISP subnet and a home/office subnet? Thanks.

#14 NpaMA

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Posted 09 May 2012 - 11:32 PM

I'll make an example up in packet tracer tomorrow. It's 11:30pm here and I really don't feel like it at the moment. Just check back sometime tomorrow night and I should have an example made.

#15 helpmeplz2

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Posted 09 May 2012 - 11:39 PM

I'll make an example up in packet tracer tomorrow. It's 11:30pm here and I really don't feel like it at the moment. Just check back sometime tomorrow night and I should have an example made.

Thanks a lot, I will check back for sure. :D




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