CCNA - subneting

Author

subneting

Andyy

2004-04-20, 7:22 am

You are the network administrator of a large company whose ip address is 172.168.0.0
Subnet the above address cosidering the following: This company has 27 departments and wants to dedicate a subnet to each department.

It also considers expanding its operations and creating another 14 departments each having its own subnet.

Further future expansion is also a possibility but will be of a very small scale (no more than 10 subnets).Each subnet is required to be able to accommodat a maximum of 350 hosts.

The 37th subnet is to be used for the management department.What is the network address of the 37th subnet ?

forbesl

2004-04-20, 8:25 am

<sniff><sniff>....smells like a brain-dump question.

stnosc

2004-04-20, 9:19 am

www.learntosubnet.com

dmaftei

2004-04-20, 5:10 pm

quote:
Originally posted by Andyy
172.168.0.0

Your question is ambiguous. On one hand you're told that you'll have at most 51 subnets (27 + 14 + 10). On the other hand you're told that a subnet should accomodate maximum 350 hosts. How you answer it depends on you want to settle for.

1. If you want to have the minimum number of subnets, you start by finding the smallest power of two bigger than 51: that's 64. To get 64 subnets from a class B network you need a 255.255.252.0 mask. Your subnets will go like:

172.168.0.0/22
172.168.4.0/22
172.168.8.0/22
etc.

You'll find the 37th among those. The catch here is that each subnet will have 1022 host addresses.

2. If you want the smalest subnets that can accomodate 350 hosts, you'll find the smallest power of two bigger than 350: that's 512. A subnet with 512 addresses (510 hosts) has a 255.255.254.0 mask. When you apply that mask to your 172.168.0.0 network you get:

172.168.0.0/23
172.168.2.0/23
172.168.4.0/23
etc.

Again you'll find the 37th yourself. The catch here is that you end up with 128 subnets, much more that the 51 you need.

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