Subnet masking..

  Gaz 25 00:16 27 Jan 2005
Locked

Hi, have any of you guys got any time just to explain subnet masking to me.

I need to know how to assign subnet masks if someone says "ok, you got 5,000 Pc's here - network them..." well, of course you need subnet masking to split the collision domain and get all the PC's on at once.

However, I'm finding it rather 'strange' to how it works... No one has really explained how it's actually found out. I need Class A, B and C IP's and subnets to be worked out please.

Can any one help me understand it at all? It just doesn't flow - but there again, no one has explained it to me completly yet, and online tutorials seem incomplete and don't teach how to work it out.

Thanks in advance.

  recap 08:42 27 Jan 2005

click here this is a tool that I have found very useful Gaz 25.

  recap 09:32 27 Jan 2005

Here is an example of how to calculate a Network range:

A network ID of 137.72.32.0/20 means that a subnet mask will be used that contain 20 1s in its binary form (The decimal equivalent of this will be a subnet mask of 255.255.240.0). The subnet mask will look like the following:

11111111 11111111 11110000 00000000

Therefore, the first 20 digits if IP addresses will represent the network ID and the last 12 digits will represent the host ID. In this case the network portion will be:

01110101 01001000 0010

The smallest host ID will be:

0000 00000001

which will yield an IP address of 137.72.32.1. Note that all zeros is not a valid host ID.

The largest host ID will be:

1111 11111110

Which will yield an IP address of 137.72.47.254. Note that ones is not a valid host ID. Therefore the available address range given a network ID of 137.72.32.0/20 will be 137.72.32.1 - 137.72.47.254

click here for further information.

  Chezdez 12:30 27 Jan 2005

unfortunately, explaining subnet masking is very difficult without actually being to write it down, and show you where each value comes from

recap has made a good effort, but to understand fully, you really need someone to show you, in person, and on paper

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