Introduction

The question

Campus A

1000 hosts

Campus B

400 hosts

Department Administration

110 hosts

10.0.0.0/8

172.16.0.0/16

192.168.1.0/24

Answer

Subnet 1 - 1000 hosts

1111 1111 . 1111 1111 . 1111 1100 . 0000 0000 = 255.255.252.0 or /22

Range:

1010 1100 . 0001 0000 . 0000 00 | 00 . 0000 0001 = 172.16.0.1 1010 1100 . 0001 0000 . 0000 00 | 11 . 1111 1110 = 172.16.3.254

Broadcast: 1010 1100 . 0001 0000 . 0000 00 | 11 . 1111 1111 = 172.16.3.255



Subnet 2 - 400 hosts

So for our second network we need at least 400 hosts. The amount of bits we need is 2^9 (512) for the hosts. And we know our first available network is 172.16.4.0.



Subnet mask:



1111 1111 . 1111 1111 . 1111 1110 . 0000 0000 = 255.255.254.0 or /23

Range:

1010 1100 . 0001 0000 . 0000 010 | 0 . 0000 0001 = 172.16.4.1 1010 1100 . 0001 0000 . 0000 010 | 1 . 1111 1110 = 172.16.5.254

Broadcast: 1010 1100 . 0001 0000 . 0000 010 | 1 . 1111 1111 = 172.16.5.255

Subnet 3 - 110 hosts

So for our third network we need at least 110 hosts. The amount of bits we need is 2^7 (128) for the hosts. And we know our first available network is 172.16.6.0.



Subnet mask:



1111 1111 . 1111 1111 . 1111 1111 . 1000 0000 = 255.255.255.128 or /25

Range:

1010 1100 . 0001 0000 . 0000 0110 . 0 | 000 0001 = 172.16.6.1 1010 1100 . 0001 0000 . 0000 0110 . 0 | 111 1110 = 172.16.6.126

Broadcast: 1010 1100 . 0001 0000 . 0000 0110 . 0 | 111 1111 = 172.16.6.127

Subnet 4 - router 1

The subnets for our routers only require 2 usable IP's. The amount of bits we need for this is 2^2 (4) for the hosts. And the first available address is now 172.16.6.128.



Subnet mask:



1111 1111 . 1111 1111 . 1111 1111 . 1111 1100 = 255.255.255.252 or /30

Range:

1010 1100 . 0001 0000 . 0000 0110 . 0000 00 | 01 = 172.16.6.129 1010 1100 . 0001 0000 . 0000 0110 . 0000 00 | 10 = 172.16.6.130

Broadcast: 1010 1100 . 0001 0000 . 0000 0110 . 0000 00 | 11 = 172.16.6.131

Subnet 5 - router 2

The amount of bits we need for this network is also 2^2 (4) for the hosts. And the first available address is now 172.16.6.132.



Subnet mask:



1111 1111 . 1111 1111 . 1111 1111 . 1111 1100 = 255.255.255.252 or /30

Range:

1010 1100 . 0001 0000 . 0000 0110 . 0000 00 | 01 = 172.16.6.133 1010 1100 . 0001 0000 . 0000 0110 . 0000 00 | 10 = 172.16.6.134

Broadcast: 1010 1100 . 0001 0000 . 0000 0110 . 0000 00 | 11 = 172.16.6.135

The amount of bits we need for this network is alsofor the hosts. And the first available address is nowSubnet mask: The subnets for our routers only require 2 usable IP's. The amount of bits we need for this isfor the hosts. And the first available address is nowSubnet mask: Summary Needed Size Allocated Size Address Mask Dec Mask Assignable Range Broadcast 1000 1022 172.16.0.0 /22 255.255.252.0 172.16.0.1 - 172.16.3.254 172.16.3.255 400 510 172.16.4.0 /23 255.255.254.0 172.16.4.1 - 172.16.5.254 172.16.5.255 110 126 172.16.6.0 /25 255.255.255.128 172.16.6.1 - 172.16.6.126 172.16.6.127 2 2 172.16.6.128 /30 255.255.255.252 172.16.6.129 - 172.16.6.130 172.16.6.131 2 2 172.16.6.132 /30 255.255.255.252 172.16.6.133 - 172.16.6.134 172.16.6.135

So for our third network we need at least 110 hosts. The amount of bits we need isfor the hosts. And we know our first available network isSubnet mask: So for our second network we need at least 400 hosts. The amount of bits we need isfor the hosts. And we know our first available network isSubnet mask:

Today I had an exam about CCNA 2 which was made by our teacher. So this was not the standard CISCO multiple choice exam. The first question was to subnet a network using VLSM. Since I do not had a guide for myself I will make this post.We have a network with the following locations:Subnet this network using VLSM with the required amount of hosts in each subnet. You can choose between the following networks:Since we have a network thathosts I choose for thenetwork. Also the serial interfaces between the routers need to be included in the subnets. So we have a total of 5 subnets in this particular network.So the first network is our subnet with at least 1000 hosts. The amount of bits we need isfor the hosts.Subnet mask: