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You can download the 200kb PDF file to see the questions I'm being asked. I'm not a networking guy and our teacher has really failed to teach the basics and just thrust us into this thing.

I have no choice but to brute force my way through this filler class.

How exactly can I decide where to subnet? For example, in my PDF does every connection between a router and a switch have to be a Subnet? Where do I apply VLSM?

Does anyone have a tutorial step by step on create a VLSM network between a couple of routers, switches and hosts.

In the PDF they show 8000h, that means I need to accomodate 8000 hosts right? I don't know how to do that.

If the question says the IP address in the beginning is 191.20.0, how can I accomodate 8000 hosts?

Edit: My main question is how to accomodate 8000h like in the PDF

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2 Answers 2

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I am only doing this because I believe you. The kids I am going to school with are lost, and we are using the cisco netacad curriculum. The answer is divide and conquer. Assuming I counted correctly this is correct, though I would have taken more time to look at how the routes will aggregate. There are gaps if you need to fix something. It took longer to count than to produce this.

Network           Net Broadcast     CIDR Mask              UsableHosts 
172.16.0.0        172.16.63.255     18   255.255.192.0     16,382      AVL  isPrivate, isClassB
172.16.64.0       172.16.95.255     19   255.255.224.0     8,190       AVL  isPrivate, isClassB
172.16.96.0       172.16.127.255    19   255.255.224.0     8,190       REQ 8000  isPrivate, isClassB
172.16.128.0      172.16.143.255    20   255.255.240.0     4,094       AVL  isPrivate, isClassB
172.16.144.0      172.16.159.255    20   255.255.240.0     4,094       REQ 4000  isPrivate, isClassB
172.16.160.0      172.16.175.255    20   255.255.240.0     4,094       REQ 4000  isPrivate, isClassB
172.16.176.0      172.16.191.255    20   255.255.240.0     4,094       REQ 4000  isPrivate, isClassB
172.16.192.0      172.16.207.255    20   255.255.240.0     4,094       REQ 4000  isPrivate, isClassB
172.16.208.0      172.16.223.255    20   255.255.240.0     4,094       REQ 4000  isPrivate, isClassB
172.16.224.0      172.16.227.255    22   255.255.252.0     1,022       AVL  isPrivate, isClassB
172.16.228.0      172.16.231.255    22   255.255.252.0     1,022       REQ 1000  isPrivate, isClassB
172.16.232.0      172.16.235.255    22   255.255.252.0     1,022       REQ 1000  isPrivate, isClassB
172.16.236.0      172.16.239.255    22   255.255.252.0     1,022       REQ 1000  isPrivate, isClassB
172.16.240.0      172.16.243.255    22   255.255.252.0     1,022       REQ 1000  isPrivate, isClassB
172.16.244.0      172.16.245.255    23   255.255.254.0     510         AVL  isPrivate, isClassB
172.16.246.0      172.16.247.255    23   255.255.254.0     510         REQ 500  isPrivate, isClassB
172.16.248.0      172.16.249.255    23   255.255.254.0     510         REQ 500  isPrivate, isClassB
172.16.250.0      172.16.250.255    24   255.255.255.0     254         REQ 250  isPrivate, isClassB
172.16.251.0      172.16.251.255    24   255.255.255.0     254         REQ 250  isPrivate, isClassB
172.16.252.0      172.16.252.255    24   255.255.255.0     254         REQ 200  isPrivate, isClassB
172.16.253.0      172.16.253.255    24   255.255.255.0     254         REQ 200  isPrivate, isClassB
172.16.254.0      172.16.254.127    25   255.255.255.128   126         AVL  isPrivate, isClassB
172.16.254.128    172.16.254.255    25   255.255.255.128   126         REQ 125  isPrivate, isClassB
172.16.255.0      172.16.255.127    25   255.255.255.128   126         REQ 125  isPrivate, isClassB
172.16.255.128    172.16.255.191    26   255.255.255.192   62          AVL  isPrivate, isClassB
172.16.255.192    172.16.255.199    29   255.255.255.248   6           AVL  isPrivate, isClassB
172.16.255.200    172.16.255.203    30   255.255.255.252   2           AVL  isPrivate, isClassB
172.16.255.204    172.16.255.207    30   255.255.255.252   2           REQ 2  isPrivate, isClassB
172.16.255.208    172.16.255.211    30   255.255.255.252   2           REQ 2  isPrivate, isClassB
172.16.255.212    172.16.255.215    30   255.255.255.252   2           REQ 2  isPrivate, isClassB
172.16.255.216    172.16.255.219    30   255.255.255.252   2           REQ 2  isPrivate, isClassB
172.16.255.220    172.16.255.223    30   255.255.255.252   2           REQ 2  isPrivate, isClassB
172.16.255.224    172.16.255.227    30   255.255.255.252   2           REQ 2  isPrivate, isClassB
172.16.255.228    172.16.255.231    30   255.255.255.252   2           REQ 2  isPrivate, isClassB
172.16.255.232    172.16.255.235    30   255.255.255.252   2           REQ 2  isPrivate, isClassB
172.16.255.236    172.16.255.239    30   255.255.255.252   2           REQ 2  isPrivate, isClassB
172.16.255.240    172.16.255.243    30   255.255.255.252   2           REQ 2  isPrivate, isClassB
172.16.255.244    172.16.255.247    30   255.255.255.252   2           REQ 2  isPrivate, isClassB
172.16.255.248    172.16.255.251    30   255.255.255.252   2           REQ 2  isPrivate, isClassB
172.16.255.252    172.16.255.255    30   255.255.255.252   2           REQ 2  isPrivate, isClassB
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You need a subnet for each link connected to a router. Each link connected to a router is a LAN segment.
You must apply VLSM everywhere. To do this you have to create smaller subnet in the 172.16.0.0/16 range for each segment.
The job here is to create subnet large enough for all host of each segment for subnet that also doesn't overlap each others.

The first step is to find the subnet size needed for each segment.
The second step will be to split 172.16.0.0/16 into subnets you need at first step.

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Thanks for the help! That makes sense somehow. How would I go about determining the subnet size needed for each segment? –  Sergio Tapia Aug 30 '10 at 11:07
    
It depends of number of host that need to be connected to the segment. Take a look to en.wikipedia.org/wiki/Subnetwork –  radius Aug 30 '10 at 11:12
    
For example 8000hosts are needed between a lan and a router. Does the number of hosts determine how many subnets I need? Can you help me with this little example of 8000h? –  Sergio Tapia Aug 30 '10 at 11:32
    
8000hosts won't be "between the LAN and router" ... they will be the LAN. So, if you need 8000 hosts in 1 subnet... then you will need a subnet with sufficent number of available addresses to support 8000 hosts + 1 for router. You can do that with a /19 quite easily. try using a good tool like: subnet-calculator.com/cidr.php On a side note... I took this class, I wouldn't consider it filler... but quite important. –  TheCompWiz Aug 30 '10 at 17:45

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