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IP addressing, masks and subnetting


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#1
SallyMae

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Because I'm drowning in information right this second, I'm having a bit of a hard time formulating my question. Perhaps I can start this the best I can and a little "back and forth" with someone will help me sort and file all the information I have and eventually figure out what I'm trying to figure out. Here's where I'd like to start:

Using CIDR notation for the following address: 192.168.5.130/24, I found some statements and a chart stating the following information for the address:

IP address: (binary - 11000000.10101000.00000101.10000010) (dotted decimal - 192.168.5.130)
Subnet mask: (binary - 11111111.11111111.11111111.00000000) (dotted decimal - 255.255.255.0)
Network prefix (binary - 11000000.10101000.00000101.00000000) (dotted decimal - 192.168.5.0)
Host part (binary - 00000000.00000000.00000000.10000010) (dotted decimal - 0.0.0.130)

The information I'm reading states, in part, "an address (192.168.5.130) and its associated /24 network mask (255.255.255.0)"

I understand the /24 comes from the 24 leftmost "1" bits in the subnet mask. What I can't figure out is how one knows that 255.255.255.0 is associated with 192.168.5.130 as a subnet mask. I do understand that certain address class ranges use from 8 to 24 bits in the leftmost bits to designate a mask but something is lost upon me about how the algorithm(?) is applied to the address so that you know which address goes with which mask. Maybe I'm getting deeper than I need to get and can just use a subnet calculator to get the information I need? I don't know. Does anybody out there understand what I'm trying to get at and can maybe help me out here?

Thanks.
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#2
Neil Jones

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This is all very well but what exactly are you trying to do with this information?
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#3
SallyMae

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I just decided I'd like to learn ip networking so I found a free online course that sends a lesson a day to your email. I was catching on fine but got a little lost when it came to figuring out the pattern between ip address and mask. I took a practice test and missed several questions that wanted me to identify networks, hosts, addresses, masks, etc. given an address in CIDR notation. From what I've read the mask does not appear to be part of the actual datagram so I figure from other wording I've read that there's some pattern between ip address and mask that links the two together. I went on the internet to do more research figuring I'd find something to help me out and ended up with a flood of information. I get the idea this might be quite a lenghty explanation. Maybe too much for this forum. Even if someone could point me to some other reading (a book, website, etc.) that'd be great.

Any way, thanks for the reply.
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#4
SallyMae

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OK, I think I can ask a more concrete question now. I've been doing some more digging on the internet and found the following information:

"Let's say your ISP has assigned you 16 IP addresses. Your workstation is set to an address of 192.168.1.9, with a mask of 255.255.255.240. Just from that, you can calculate the rest of the addresses that belong to you: 192.168.1.8 through 192.168.1.23."

Using this information,can someone break down for me and be more explicit about just how from a mask of 255.255.255.240 and an address of 192.168.1.9 one can calculate the rest of the addresses in the above example.

Thanks.

Edited by SallyMae, 27 October 2011 - 01:34 PM.

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#5
SallyMae

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Well, I've been digging and scrounging. I think maybe I'm getting "warm", here. Can someone tell me if the answer to my question lies somewhere in what is called "bitwise operations"?
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#6
LouZiffer

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.

Edited by LouZiffer, 16 November 2011 - 06:44 PM.

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