# Subnetting, partition ip addresses. networking



## bawse.c (Sep 29, 2011)

Hi,

I am trying to figure out a way to partition the departmental IP network address block to create a staff and a student subnet. Each of these will be identified by its own network address and netmask. It is university policy that you must be economical with the IP addresses. That is, the subnets must be as small as possible, but they must be large enough to accommodate the maximum number of hosts you were given. 

Also, it is university policy that the respective gateway router to the outside 
world should always be given the highest possible host IP address in the subnet. 

The student subnet should have a higher IP network address than the staff subnet. 

The network must be able to support up to 60 machines on the staff subnet (not counting the router) and up to 120 machines on the student subnet (also not counting the router).

IP address/netmask
University network address	127.158.128.0
University network mask	255.255.192.0
University internet gateway IP address	127.158.191.254
Department network mask	255.255.254.0
Department router address	127.158.129.254


Suppose that the network address of the departmental network is 127.158.128.0 (calculated by AND between Dep network mask and Dep router address)


I know that 60 machines would use 6 bits for the staff subnet.
the netmask of staff would be 255.255.255.192.

how can I figure out the the IP network address of the staff subnet.
I have worked out the range for the staff subnetwork.

127.158.128.0 - 127.158.128.63
127.158.128.1 = Gateway address
127.158.128.63 = Broadcast address

Now how can I calculate the IP network address of the staff subnet??

Please help its urgent


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## heliuminside (Sep 25, 2011)

First of all you cannot use the subnet 127.0.0.0, it is reserved for loopbacks.
However you can yo use either of these private addresses:

10.0.0.0/8
172.16.0.0/16
192.168.0.0/24

Policy requirements: a subnet for staff 60 machines and a subnet for students 120 machines.

Policy states that staff machines should use the first part of subnet and students one the second.

I would not recommend you that design because if you put 60 machines first you will end up eating address space. Take it like this:

Staff subnet: 172.16.1.0/192 you will use the space 0-63 however in order to apply the second part to this subnet you need to eat up to another 64 addresses, because you cannot start subneting from smaller networks to bigger ones. This would look like this:

Staff part is 172.16.1.0 - 63 /192 (*255.255.255.192) and for the students part it would be 172.16.1.128.0/128 (*255.255.255.128)

So you would waste 64 addresses, but let's not call it waste because you will be able to squeeze another subnet for 64 addresses between staff machines and students one.

If I were you I would do it this way:

Students 172.19.50.0/128 (assign machines addresses .1 through .125, for router use .126 and your broadcast would be .127)

Staff 172.19.50.128/192 (assign machines addresses through .129 through .189, for router use .190 and your broadcast would be .191)

You can use the similar schemes for every class group you just need to start subnetting from the bigger part first.


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## bawse.c (Sep 29, 2011)

The thing is that I have to do it the way they have provided and use the network ip address they have provided. You see its just theory work and not practical so the numbers wont matter but it has to be calculated properly.


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## heliuminside (Sep 25, 2011)

bawse.c said:


> I know that 60 machines would use 6 bits for the staff subnet.
> the netmask of staff would be *255.255.255.192*.
> 
> how can I figure out the the IP network address of the staff subnet.
> ...


You have already worked out the staff range so let me fill your students range.

127.158.128.128 - 127.158.128.254 (usable IP range 129 - *254*)
127.158.128.*254* - Gateway address (Router IP)
127.158.128.255 - Broadcast address
Subnet mask: *255.255.255.128*

That would be your homework however if you'd apply this in real world you would not use the IP range efficiently because you have eaten some space from the range.


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## bawse.c (Sep 29, 2011)

*Thanks Helium =) 

I managed to work it out last night and I am glad I got the same answer as you!

You are a legend !*


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## heliuminside (Sep 25, 2011)

You are welcome! Glad to here you know how to subnet.


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