Am I subnetting this correctly?

[dehlert]

I'm tasked with creating a network that has been assigned the 10.11.12.0/23 network address for all computers and devices. It should have 3 subnets for classrooms, office management, and public use.

Working through binary, I cam up with this. Please let me know if I'm on the right track as I spent countless hours trying to grasp this.

Using the power of 2 now have 4 sub nets:
10.11.12.1 - 10.11.12.126
10.11.12.128 - 10.11.12.254
10.11.13.1 - 10.11.13.126
10.11.13.128 - 10.11.13.254

All using the subnet mask of: 255.255.254.0
All using a broadcast address of: 10.11.13.255

I felt like I was writing in another language but if anyone can confirm this or has any tips they may know of to help me in the future, that would be most helpful. Thanks!

 

[PizzaTheHutt]

For three subnets, why not create three VLANs and use them with an entire subnet each - client separation will really help you in the future.

 

[dehlert]

For three subnets, why not create three VLANs and use them with an entire subnet each - client separation will really help you in the future.

Thank you for the quick response, but per the assignment, it asked specifically for 3 subnets unfortunately. But that is a great idea for an after-mentioned thought.

 

[jsmithepa]

For three subnets, why not create three VLANs

Is homework.


OP, u may wanna GOOGLE, there are tricks that can do this faster.

 

[PizzaTheHutt]

If it's homework, I would put:

10.11.12.1 - 10.11.12.254
10.11.13.1 - 10.11.13.254
10.11.14.1 - 10.11.14.254

 

[dehlert]

Thank you! I just want to make sure through my studies though that the above 4 subnet addresses and ranges are correct?

 

[PizzaTheHutt]

The ranges in an IP each go up to 255 possible values (0-254). The subnets are (technically speaking) governed by the third "chunk" of the address (e.g. 192.168.1.1 and 192.168.2.1) and the nodes connected each get a different fourth "chunk" (e.g. 192.168.1.15 and 192.168.1.24). This is all a generalisation but I hope it helps.

 

[dehlert]

If it's homework, I would put:

10.11.12.1 - 10.11.12.254
10.11.13.1 - 10.11.13.254
10.11.14.1 - 10.11.14.254

How could I do that if the mask is /23
I changed it to /25, for the 4 subnets but I need at least 254 on one subnet.
Sorry if I'm being confusing.

 

[Kewlx25]

For three subnets, why not create three VLANs and use them with an entire subnet each - client separation will really help you in the future.

Thank you for the quick response, but per the assignment, it asked specifically for 3 subnets unfortunately. But that is a great idea for an after-mentioned thought.

Even though the assignment hasn't asked this, you should be aware that you should NEVER have more than one subnet per broadcast domain. I assume this is an entry level assignment that is just trying to get you familiar with subnets, then routing, then VLANs.