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Author Topic: Subnetting  (Read 1687 times)


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« on: Jun 22, 2014, 03:44 PM »
I'm fairly certain I understand what subnetting is and how to do it, but my assignment seems to be asking me for a configuration that isn't possible.  I'm wondering if someone who understands subnetting already would be able to make sense of it.  The assignment text is listed below:

Quote from: Assignment
Your IP address is You will need to subnet this address to get 10 networks and 9 hosts per network. You will need to complete the following and show your work:


1. Custom Subnet Mask

2. Network Addresses

3. Host Addresses

Now as I understand it, you can set up the number of networks in powers of 2, so dividing a 255-address pool by 10 would leave leftovers.  Likewise, trying to get 9 nodes per network would also leave leftovers. (notice how they dont specify whether those 9 nodes include or exclude the network and broadcast addresses, im assuming they exclude it since it specifically says 9 "hosts" and not nodes.)

Can anyone else make sense of this?  Should I just do as it says and ignore the leftovers at the end? Or should I just do the next best thing and round up to 16 networks of 16 nodes?
« Last Edit: Jun 22, 2014, 03:48 PM by Bastian »

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Re: Subnetting
« Reply #1 on: Jun 22, 2014, 04:56 PM »
I'm looking at it too, and anyway I try to figure it out I still come up with going with the 16 option instead of with less. One of the biggest rules I was told over and over again while I was working on Cisco was that no matter what you settled on, you always have to leave room for expansion in a company. I'd say it's better to have leftover than to have not enough, but maybe someone with more expertise in this matter will hopefully chime in with some advice for you Cody.

If I can think of anything else, I'll edit my post. Until then, good luck!


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Re: Subnetting
« Reply #2 on: Jun 22, 2014, 07:26 PM »
16 subnets, 14 hosts per.

Can't really do anything else. If the host counts were variable, you might be able to get away with some VLSM jiggery-pokery for extra credit or some shit, but they aren't.

Gotta work in powers of 2. (2^4 and 2^4 in this silly case.)
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Re: Subnetting
« Reply #3 on: Jun 22, 2014, 09:16 PM »
That's why the question kinda confuses me too. The assignment asks for custom masking, but if they only want 10 networks with 9 hosts each then VLSM isn't even considered in this at all. I could understand if they asked you for 10 networks with a varying number of hosts, but they only ask for 9 each.


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Re: Subnetting
« Reply #4 on: Jun 24, 2014, 08:07 AM »
You have to go up to the next power of 2.   Just because they want 10 networks doesn't mean you can't give them MORE.... it's like the price is right. 


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