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TOPIC: Problem With Subnets!

Problem With Subnets! 8 years 6 months ago #33061

Hi All!!

http://www.tech-faq.com/subnet-mask.shtml

I have checked out this forum, in it's content there is a calculation part

An example using an IP address of 156.154.81.56 used with a network mask of 255.255.255.240 follows:
IP Address: 10011100.10011010.01010001.00111000
Subnet mask: 11111111.11111111.11111111.11110000
Bitwise AND


Result: 10011100.10011010.01010001.00110000


What does the Result refers to? I know how they count how many hosts can there be in a subnet but I dun understand why need to get the Result.

In it there's this too

You must also subtract two from the result because one address is reserved for broadcast and network addresses.


what is the broadcast for?

Last question: host=user right?

can anyone explain to me please, I appreciate your help:wink:

Grateful to all!

FishnBone

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Re: Problem With Subnets! 8 years 6 months ago #33064

  • SteveP
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What does the Result refers to?

I'll tackle the first part first by asking you a question:

What is the function of the subnet mask?

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Re: Problem With Subnets! 8 years 6 months ago #33092

Hi SteveP!

Sry for the late reply, erm the function of the subnet mask is to hide the internal network of the company

Fishnbone

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Re: Problem With Subnets! 8 years 6 months ago #33095

  • SteveP
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Sry for the late reply, erm the function of the subnet mask is to hide the internal network of the company

Wrong - you're thinking of NAT (Network Address Translation).

Maybe you should look at some articles about IP addressing and subnet masks. You'll receive lots of help here (I certainly have) but I doubt if anyone will spoonfeed you. It helps to have a basic understanding and then explain in detail the part(s) that you don't understand and I'm sure that someone will walk you through the bits that don't fall into place.

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Re: Problem With Subnets! 8 years 6 months ago #33097

Hi Fishnbone, the Bitwise "AND" operation is used to determine what subnet a given IP address lives within. In your case, the IP address (or host) is 156.154.81.56. By converting that IP address and the subnet mask into binary numbers and "AND-ing" them together you get the result of 156.154.81.48, which is the actual subnet address. The subnet mask of 255.255.255.240 allows for subnets with 14 usable host addresses. In your case, the range of usable IP addresses is 156.154.81.49 to 156.154.81.62. You cannot use the subnet address of 156.154.81.48 or the broadcast address of 156.154.81.63. The broadcast address is typically used when a host needs to communicate with another host and does not have that hosts IP address / MAC address in its ARP cache. For example, if your host 156.154.81.56 wants to communicate with host 156.154.81.50, it first needs to know what MAC Address to forward that request to so it floods the entire subnet with a broadcast asking who has 156.154.81.50 and what is your MAC address. Once it receives a reply, it caches that information in its ARP cache and begins communication. The switch then forwards the packets to the appropriate switch port based on the MAC address in the header.

Does that help?

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Re: Problem With Subnets! 8 years 6 months ago #33132

Hihi!

SteveP: icic ok i shall try looking and finding articles about it

Gipper: Thank you for your detailed explanation i shall look and understand it thoroughly. and yes it was helpful!


Thank you all for helping!

FishnBone

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