Here are the requirements starting with the network.
One seven, two point sixteen Dot 1.0 slash 24.
I need to subnet this network into one two three four five six seven subnets.
The requirements for each subnet are listed.
125 hosts over here.
59 hosts over here between the routers.
Two hosts, each coming off the router.
That's the edge router that connects to the internet.
We have a DMZ which needs 25 hosts and coming off of the router here, we need a 12 hosts network for
management when creating subnets.
We have to remember that the sizes of subnets that we can create are constrained by the binary place
values.
The binary place values, if you look at eight bits, are 128, 64, 32, 16, eight, four, two and
one.
In other words, we cannot create a subnet specifically for 125 hosts, but we can create a subnet for
128 hosts, two of which are not usable, so it would be effectively 126 hosts.
In other words?
We can create subnets for one hundred and twenty eight minus two hosts, which meets the requirement
of 125 hosts.
Similarly, instead of 59 hosts, we can create a subnet for 64 minus two hosts, meaning 62 usable
hosts.
For the management network, instead of 12, host will create a subnet for 16 minus two hosts or 14
usable hosts.
For the point to point networks of two hosts, each will use the place value of four to create four
minus two usable hosts per subnet and for the DMZ network will create a subnet of 30 to minus two or
30 usable hosts.
This will meet the requirement of 25 hosts for the DMZ.
So now that we know the sizes of the subnets will need to create, we need to ask ourself if the network
that we're starting with has enough address space to accommodate these networks.
Currently, the one seven two six one zero network is slashed 24, meaning it's a 256 hosts network
or 256 minus two, is 254 usable hosts.
If we add 120 eight plus 64 plus 32 plus 16, we get 240.
Add four, eight and 12 more.
We get two hundred and fifty to two hundred and fifty two hosts is less than 256, so we should have
enough address space in the one seven two six one 1.0 network to accommodate these seven subnets.
So now that we figured out the different sizes of subnets that we're going to need to create, I have
listed them out here working from largest to smallest and starting with the one seven two six one zero
subnet.
The question is what will the subnet mask be?
Currently, the subnet mask is slashed 24 to create a subnet for 128 minus two hosts will need to borrow
one bit.
The 128 bit in the binary place values.
This will create a subnet mask of twenty five ones.
You can see the one bit here in the one hundred and twenty eighth place.
This is a slash 25 subnet mask, so I'll put in twenty five here and you can see that we now have a
Slash 25 subnet mask.
This creates 128 minus two usable hosts for two reasons.
The first reason is the last one is our subnet multiplier and the subnet multiplier.
The one here is in the 128th place.
This means that the networks will go up by 128.
Also, the zeros that are left over in the host portion are seven zeros and two to the seventh power
is 128.
In other words, we have 128 values in the host bits minus two makes 126 usable hosts.
So the one seven two six one zero gets a slash 25 subnet mask, creating a network that goes from zero
to 127.
And the next network will start at one hundred and twenty eight.
Now, how many bits do we need to borrow from the host portion to create a subnet starting at 128 for
64 minus two usable hosts?
To create this subnet will need to borrow two bits from the host portion of the subnet mask.
Notice that now we have a slash 26 subnet mask because there's 26 ones and the subnet multiplier is
in the 64s place.
We have six zeros in the host bits, meaning two to the sixth power is 64.
So we have 64 minus two usable hosts.
With the subnet multiplier in the 64s place, the sublets now go up by 64.
So the next subnet will be one hundred and ninety two.
With the next subnet, starting at 192 to create a subnet for 32 minus two usable hosts will need to
have the subnet mask and at the 32s place, the subnet mask will now look like this.
You can see we have 27 ones to make a slash 27 subnet mask.
The last one in the subnet mask, the subnet multiplier is in the 32s place, so the networks will now
go up by 30 to.
Slash, 27, is now our subnet mask.
The networks will go up by 32, so starting at 192, the next network will be two 24.
To create the next subnet of 16 minus two usable hosts will need to change the subnet mask to slash
tape.
Now I'm borrowing one two three four bits from the host portion of the subnet mask.
I've got four zeros or two to the fourth power creating 16 hosts.
The subnet multiplier is in the 16's place, meaning the networks will go up by 16.
So we now have a slash 28 subnet mask with 28 ones.
The networks now go up by 16.
So the next network will start at two 40.
For the final three, subnets will change the subnet mask to slash 30.
Now we're borrowing six bits from the host portion of the original subnet mask for host bits.
We only have two zeroes or four values in the host portion of the subnet mask, creating four minus
two or two usable hosts per subnet with the subnet mask at EGX30.
The subnet multiplier being in the first place.
The network's go up by four.
So we now have the 240.
To 44 and to 48 subnet notice that 240 has four hosts, two usable hosts, the next subnet starts at
244 and the following subnet starts at 248.
These subnets are now all slash 30.
We can clearly see that with a slash 25 subnet mask.
We have a subnet multiplier of 128 and we have 128 minus two usable hosts.
The next network starts at 128 with the 128 network.
We have a slash 26 subnet mask.
The subnet multiplier 64.
So the next network starts at 192.
The 192 network has a 27 subnet mask with the subnet multiplier in the 32s place.
So the next network starts at 224.
The 224 Subnet has a 28 subnet mask with a slash 20 subnet mask.
The subnet multiplier is in the 16's place, making the next network start at 240.
It goes up by 16.
The 240 subnet has a 30 subnet mask, which is in the Ford's place, or the subnet multiplier being
a four.
And the network now goes up by for the 02:44 network also has a slash 30.
So the network goes up by four.
And so the last network is a 248 network slash 30, meaning the subnet is size four or four hosts two
usable.
If you do not count the network and broadcast address, we now have all of our subnets noticed there's
no overlapping address spaces.
The first subnet goes from zero to 127.
The next subnet goes from 128 to 191.
Next.
Network 192 goes from 192 to 223.
And you can see that none of the address spaces overlap and the subnet mask is sized for that particular
subnet.
I can now go and put all of the subnets into their proper places within the topology.