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Let's say provider granted me IP addresses 10.20.30.1 - 10.20.30.254, so the subnet address is 10.20.30.0 and mask 255.255.255.0. I set my router to 10.20.30.1 and computers to 10.20.30.2 and higher.

Now, what is the difference between accessing computer 10.20.30.2 from inside this subnet (10.20.30.3) and from outside of it (12.34.56.78). Which features or protocols will/won't work from outside. What is the purpose of creating such subnets?

Youda008
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  • Can you explain me, why do you downvote this question? i see nothing wrong with it. I really dislike the guys, who just hang around, clicking down button on everything they see and don't even bother to say why. – Youda008 Sep 21 '15 at 13:18
  • What about the girls who just hang around, clicking down button? Are you OK with them? In any case, the downvoters *are* saying why: if you hover over the downvote button, it says "This question does not show any research effort; it is unclear or not useful". That is what downvoters are saying. – womble Sep 21 '15 at 20:55

2 Answers2

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The main aim of subnetting is, to reduce network size and thus the traffic with in the network. Ofcourse we'll be able to communicate between different subnet, but that particular time only the traffic will cross the subnet. and yes, accessing from a public ip involves NAT. When/why to start subnetting a network?

Community
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First of all, you choose your own subnet for the internal network. In most cases it's a 192.168.0.0/24 network.

Now about the external subnet, that's the public IP address (assigned by the ISP). This is what identifies you on the internet. Because internal subnets aren't unique, it's impossible for devices to know how to reach you if you would only use your internal IP address. So routers mostly use NATting to translate your internal IP to a public (external IP).

So in conclusion, internal subnet is for your local network at home and external subnet is the public IP assigned by the ISP to identify you on the internet.

This is just how the cookie crumbles, nothing else.

CustomX
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  • I wasn't talking about home networks with NAT, i was talking about networks, where each computer has own public IP – Youda008 Sep 21 '15 at 14:23
  • What's the difference between home networks with NAT and your example? You're still using NAT on your router .. – CustomX Sep 21 '15 at 15:16
  • Yes, i'm using it (at home), but i wasn't asking about it. Companies, universities and other bigger organizations still use the explained type or sub network – Youda008 Sep 21 '15 at 19:29
  • @Youda008, companies, universities, etc use the same setup .. – CustomX Sep 21 '15 at 21:26