Subnetting Question

Hello there, I am currently doing a networking subject at College and would appreciate some guidance on a homework question I got. I am still getting my head around subnetting.

**Please note I have modified the original question for academic integrity purposes so that this post is for guidance, not for direct answers**

“You work for a growing international company that has five sites around the world, they now require a new addressing scheme for their entire network. At each site, there is a router that will connect to this network. The amount of workstations expected in each site as follows:

Site 1 - 180 workstations

Site 2 – 410 workstations

Site 3 – 220 workstations

Site 4 – 109 workstations

Site 5 – 170 workstations

You have received a criteria for designing this network with the following

- Must utilize 10.0.0.0 private IP address

- The network should cover the five sites

- Each site to have their own single subnet

- Addressing solution must be simplified and straightforward to administer

- Allows up to 2000 devices per site in the future

- Reduce the amount of IP address space wasted”

The instructor said that there is no one correct solution and that the reasoning behind your proposed solution is the important part.

After doing some research and using the VLSM/CIDR calculators. I came up with two possible solution if I am getting the criteria and subnetting parts right…

Solution 1

Use 10.0.0.0/13 for entire network with /16 mask for each subnet would allow up to 8 subnets with 65534 address available at each subnet.

Site 1: 10.1.0.0 – 10.1.255.255 - 10.1.0.0 /16

Site 2: 10.2.0.0 – 10.2.255.255 - 10.2.0.0 /16

Site 3: 10.3.0.0 – 10.3.255.255 - 10.3.0.0/16

Site 4: 10.4.0.0 – 10.4.255.255 - 10.4.0.0/16

Site 5: 10.5.0.0 – 10.5.255.255 - 10.5.0.0/16

10.6.0.0-10.7.255.255 – reserved for future use

Very simple addressing solution where each site is labelled accordingly by using the second octet. The third octet could be used to label floors, areas, departments etc. I think the downside is that a lot of the IP address space is unused and could have major performance issues if not broken down using VLSM/VLANs/DHCP correctly etc.

Solution 2

Use a 10.0.0.0 /18 for the entire network with /21 mask for each subnet allows up to 8 subnets with 2046 addresses available at each subnet.

Site 1: 10.0.0.0 – 10.0.7.255 - 10.0.0.0 /21

Site 2: 10.0.8.0 – 10.0.15.255 - 10.0.8.0/21

Site 3: 10.0.16.0 – 10.0.23.255 – 10.0.16.0/21

Site 4: 10.0.24.0 – 10.0.31.255 – 10.0.24.0 /21

Site 5: 10.0.32.0 – 10.0.39.255 - 10.0.32.0 /21

10.0.40.0 – 10.0.63.255 - reserved for future use

Although more complex in addressing, allows growth and IP address wastage is more minimized. VLSM/VLANs can be used to break down the subnet at each site.

I am leaning towards Solution 1 as the question seems more focused on simplicity, room for growth and less emphasis on reducing IP address wastage.

Any feedback or thoughts would be greatly appreciated.