I just started networking and was given this exercise I'm trying to determine how many subnets are needed for this network.:

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The main network ID is Given that I know that this is a class B IP address and the subnet mask is Based on my calculations maximum number of subnet with the given information is 11. But since I have 4 routers and 6 switches, I won't need more than 10 subnets. To achieve this should I change the network id to which will give me a subnet mask of where I will get 14 maximum number of hosts. Is my logic correct or am I missing something?

  • I'm just impressed with the graphic :) – Thufir Feb 26 '18 at 19:19

For me the better is use the different 3rd octet and have a appropriate netmask.

For example

4 Routers and internet router :

Different hall (s1 to s5)

192.168.{1-5}.0/29 (if you add hall you can add appropriate number)

And DMZ :

In this configuration you can change netmask if the number of pc's or server is increases.

To calculate your netmask, in Linux you can use the package ipcalc to view your lan, broadcast and differents hosts ip's :


You can use the 4rd octet to all subnet in gateway. For example 192.168.x.1 = gateway for subnet x

To manage your ip you can use nipap (open-source address management)

For the computers, if you need dynamic IP address, you can add a DHCP Server in your DMZ, and add DHCP Relay in yours routers.

For the type of connexions, RJ45 cat. 5 or 6 is suffisent between computer and switch. Between router you can use RJ45 cat. 6 or the fiber.

  • How can I determine the ip address of the gateway? Will it be with respect to each switch or router in the setup? And how can determine the type of wires to use for my connections? – 9it3e1 Dec 8 '16 at 11:41

You'd always want to have the lowest amount of ips per subnet possible so you don't missuse any of them.

For your case, with 6 ips/subnet is enough so you'd have a mask of which is the same as

  • Upvoted since this is a corrct answer to the question the OP wanted. But 'always' is not always. You want an as big as possible (or at least big enough) subnet to cover you with future expansion. Which is theory/exam vs practice. – Hennes Dec 11 '16 at 13:16

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