Configuring subnets quandry

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I am learning the basics of subnetting however am faced with a dilemma on approaching the issue. For example I have been tasked to set up a network with 20 hosts using a Class C network addressing scheme which I understand to be with the default subnet mask of Now I understand that it leaves me with 254 hosts 0 being the subnet and 255 being the broadcast.

So if I have 20 hosts to setup that leaves 234 host spaces wasted unless the network grows to include that many hosts. Based on the requirements of 20 hosts I have the following questions.

  1. How do I accommodate future growth e.g. how many hosts do I allow for?
  2. If I were to simply restrict the number of hosts to 20 I take it that would leave me with a /27 subnet i.e. Is that right?
  3. If 2 point is correct I would have 8 subnets with the following network subnet address, broadcast addess and starting and ending host address. Is that right?
  4. If 3 is right do I still a router to allow each subnet to communicate with one another?

Subnet addresses

The broadcast address of each of these would be

The starting and ending host addresses for each of these would be - - - -

Unless I have understood it incorrectly my host addresses should be as follows as opposed to what I thought they were above  - - - - - -


  1. You’re totally right, 254 hosts are allowed, so you can add 234.
  2. Exactly, /28 would be too small, /27 fits fine (30 hosts allowed)
  3. Exactly.
  4. If you have a router, it can route traffic between the subnets (if they’re connected of course and the router knows how to route between them).

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