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Appropriate subnet address ranges

By allamp ·
I have been given IP addresses from 129.196.140.0 thru 129.196.143.255. From those addresses I must create 6 subnets to accomodate segments with as few as 2 NICs to as many as 135 workstations. And I need to figure out the appropriate subnet mask for each address range. If I use 8 bit slots for host addresses (to accomodate the 135 workstation subnet), then I only have 4 subnets (x.y.140.0, x.y.141.0, x.y.142.0 and x.y.143.0). I can't figure out how to get 6 subnets and still have enough host IDs for the 135 workstation subnet. allamp@foxinternet.net

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Appropriate subnet address ranges

by donq In reply to Appropriate subnet addres ...

140.001; 140.002; 140.003; 140.004;.......
141.001; 141.002; 141.003; 141.004;.......
142.001; 142.002; 142.002; 142.004;.......
143.001; 143.002;.......
144.001; 144.002;.....
145.001; 145.002;...
146.001; 146.00...

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Appropriate subnet address ranges

by allamp In reply to Appropriate subnet addres ...

Thanks for the effort, but my available address range is not that large. I only have the space from x.y.140.0 through x.y.143.255. I appreciate your effort though. Al

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Appropriate subnet address ranges

by -Q-240248 In reply to Appropriate subnet addres ...

You must use variable-length subnetting, since you don't have enough addresses to accomodate 6 subnets with at least 192 hosts each, which will be the maximum size you'd need (135 hosts). You will also have to subnet using a class C subnet mask on your smaller subnets (2 hosts). Start with a mask that will give you the 6 subnets. THen you'll need to break down some of the subnets, dividing them amongst your smaller networks. It depends upon your hosts and their locations within the IP scheme. You'll then need a router with multiple ports to support not only 6 networks, but also VLSM and classless subnetting. I cannot think clearly enough to give you the subnet mask you will begin with, but with a little time, I could figure it out for you.Email me if you need more info..

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Appropriate subnet address ranges

by allamp In reply to Appropriate subnet addres ...

Thanks for the help Marc. If I could find your email address I would love to show you the answer I came up with (also with significant insight from Don's answer #4 below). Al at allamp@foxinternet.net

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Appropriate subnet address ranges

by kfedor In reply to Appropriate subnet addres ...

This is impossible. The issue in that you can
not exactly obtain a subnet mask that fully cover you 135 host. I mean that 135 lay in range from 128 to 255 that correspond with consecutive ip subnet 255.255.255.128,
255.255.255.0.
In first mask you obtain subnet with max 126 hosts, with second mask you obtain subnet with max 253 hosts.
Solution: You mast revise you requirement to obtain subnet with 135 hosts.

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Appropriate subnet address ranges

by kfedor In reply to Appropriate subnet addres ...

This is impossible, if you will 6 subnets with max 135 hosts, but if you will that some subnets will be less than 135, than VLSM will be decision, of course.

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Appropriate subnet address ranges

by allamp In reply to Appropriate subnet addres ...

Thanks for taking your time to consider my addressing problem, but I'm pretty sure that it is possible. Here's why: If I use a subnet mask of 255.255.255.0 on just the 129.196.140.1 thru 129.196.140.254 portion of the available address space I can accomodate the 135 node segment. That still leaves over 750 IP addresses to handle to remaining 5 subnetworks, which consist of 58 nodes, 35 nodes, 26 nodes, 3 nodes and 2 nodes. That means I only need addresses for about 125 more nodes. Don'tyou agree that there must be some way to apply subnet masks to the remaining address range to provide addresses for the remaining 5 subnetworks? Al

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Appropriate subnet address ranges

by dlw6 In reply to Appropriate subnet addres ...

You must use Variable Length Subnet Masking. It's only a bit more complicated than regular subnetting.

I don't have exact numbers of hosts for each of your segments, so the following walk-through is just an example.

For your large (135-host) networks, use a 24-bit subnet with a mask of 255.255.255.0. Let us say that one is x.x.140.0 for the large network, and x.x.140.3 for another large network.

Now, say you have a medium-sized segment with no more than 60 hosts. For that you can usea 26-bit mask (255.255.255.192). Let us say you have two of those which can be x.x.141.64 and x.x.141.128 for two medium sized networks, and if you need two more medium ones you can add x.x.142.64 and x.x.142.128.

At this point, you have two Class C sized subnets and four 60-host sized subnets, but you can squeeze even more out of it with VLSM.

Now, let's say you need more small networks of 30 hosts each. You use a 27-bit mask for these, and (this is where it gets tricky) you can use the space that was wasted by the subnets I already named above. For example, you can use x.x.141.32, x.x.141.192, x.x.141.32, and x.x.141.192 with a mask of 255.255.255.224.

Your 6-host networks could use a mask of 255.255.255.248 with network addresses in the range of x.x.x.8, 16, 24, 224, 232, and 240.

This example gives you two Class C-sized, four 60-host, four 30-host, and 12 6-host networks, all from only the 4 Class C's you started with.

The hard part is keeping track of the different subnets. You'll want to diagram it out, and if you hook it up and machine A can see machine B but B can't see A, then you'll want to check the subnets on each.

VLSM makes more sense if you chart the possibilities out, and if you e-mail me at don-willadsen@us.army.mil I'll share my chart with you.

Good fortune,
Don

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Appropriate subnet address ranges

by allamp In reply to Appropriate subnet addres ...

Thanks for your help Don. Al

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Appropriate subnet address ranges

by allamp In reply to Appropriate subnet addres ...

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