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# Subnetting

4 replies to this topic

### #1 worlock

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Posted 13 June 2011 - 05:58 AM

With a network address of 204.15.5.0/24 what would be the order of 5 subnets. The largest subnet would have to support 28 host addresses.
Any ideas?

Thanks, :help:
Worlock

### #2 evaanscook

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Posted 18 July 2011 - 10:00 PM

Subnetting is a network design strategy that segregates a bigger network in to smaller parts. All systems that are assigned to a specific subnet will share values that are common for both the subnet and for the network as a whole. It involves the use of several tools in order to establish the series of subnetworks and permit them to still function as a complete technique when necessary. There is the matter of connectivity.

### #3 Insomnia

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Posted 22 July 2011 - 09:35 PM

QUOTE (worlock @ Jun 13 2011, 01:58 PM) <{POST_SNAPBACK}>
With a network address of 204.15.5.0/24 what would be the order of 5 subnets. The largest subnet would have to support 28 host addresses.
Any ideas?

Thanks,
Worlock

You may need to explain this better.

You're already given a subnet with a mask of /24, are you subnetting this given range into smaller networks?  I have no idea what you mean by order, IP range maybe?

Assuming you want to create 5 equal subnets using a single common subnet mask, within the range you are given, your mask would need to be 255.255.255.224, or /27.

This would allow for up to 8 (or 2^3) subnets, with the ability to support 2^5 (32) actual IP addresses per subnet.  Of these IPs, 30 are addressable, as two are required for broadcast communications.  This meets the requirements of the question.

IP ranges would be
0-31
32-63
64-95
96-127
128-159
160-191
192-223
224-255

How to find the number of IPs:
A full IP number is a 32-bit number made up of four octets, (32/4) = 8 bits per octet.  This means that each octet has 2^8 = 256 possible combinations to make up that octet's number.  When you subnet an octet, you are dividing which numbers are assigned to which subnet.  In this case, since we have to divide the last octet into 8 subnets, 3 bits are required for use to define subnets. 8 = 2^3: this is where 3 comes from.

This means that: 2^8/2^3 = 2^5, 32 IPs are used per each subnet.  Simplification shows that 8 - 3 = 5 (bits).

2^8 = total combinations allowed in the octet, 2^3 = required combinations to define this particular subnet.  2^5 = IP combinations per each subnet.

How to find the subnet mask:
Subnet mask is found by taking the highest addressable value (255) and removing the number of IPs per subnet (2^5)
This becomes 255 - 2^5 = 255 - 32 = 224.

I can explain this more indepth and at the binary level, but this should be sufficient.  Hopefully you understand what I'm trying to show you.

Edited by Insomnia, 22 July 2011 - 09:42 PM.

### #4 nelsonheell

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Posted 17 August 2011 - 01:34 AM

Subnet is the network design strategy that separates the largest network in the small parts. And all regulations that are assigned to specific sub-network share the values ​​that are common to both the subnet of the network as a whole.

### #5 absolute40

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Posted 25 August 2011 - 07:53 AM

Here are some cool Cisco subnetting and binary games I found on the Cisco site to help practice your subnetting skills!

Subnet Game
Binary Game
Subnet Troubleshooting Game
CCNA Certified

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