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Subnetting assignment

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Hello all, 

Been quite a long time since I've posted on here. Hope everyone is doing well! I figured what better place to turn to than the knowledgeable users of testmy.net?! 

I'm in a networking class and one of our homework problems has me stumped. I understand the general concept of subnetting but I am struggling with this. 


I get /16 translates to a subnet mask of (/16 in CIDR) I also understand we're subnetting the whole third octet but this part confused me as  we shouldn't need the WHOLE third octet subnetted if we've only got 3 networks with 5 hosts per?  The problem is below. Any assistance would be greatly appreciated as I have quite a few more similar problems to work through. P.S if this is the wrong section I apologize :) 


A router at your main company location is connected to your provider and 3 internal locations. The network address from your provider is Each location has a maximum of 5 nodes

Assume you are using the entire byte 3 for subnets

A. What are the 1st 3 and last 3 possible subnets to the three locations?
B. Assume you have decided to use the 1
st 3 subnets
B1. what are the 1
st and last 4 host addresses on each subnet?
B2. what is the broadcast address on each subnet?
C. What is the new subnet mask?


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So what exactly is the issue? If you're using the entire third byte as your subnet block, your new mask would be, or /24.


Which means the first subnet is, then,, etc.


They're probably asking you to use the entire third block so that it makes an easy beginner question. Otherwise you would be able to get away with a (/29) instead. Which would give you exactly 5 host addresses, 1 gateway address, 1 network address, and 1 broadcast address. The problem with this is that it's not as easy of a beginner question. (Your first subnet is to, then to, etc.)




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