CTI Technician Training Internet Protocol Part 2

Review Is this address on your network? Your info Destination IP Convert IP and subnet mask to binary Draw a line between network bits and host bits. Convert Destination IP to binary. Check to see if network bits match. Don’t Match No it is not.

Calculating hosts from a mask Number of hosts per subnet can be calculated by finding all of the possible host addresses. (Remember not to count the network id and broadcast address.) The formula used for calculating number of hosts is: 2 n -2 n = number of host bits You have to -2 because the network id and broadcast address cannot be used as host addresses.

Subnetting Definition Dividing a larger network into smaller, equally sized networks. Example: If given a /16 network, it can be divided into 256 separate /24 networks.

To calculate subnets, you must find all of the differences between the larger mask and the smaller mask. This will give you the network id’s of your new smaller networks /

Calculating networks from a subnet mask To find the number of subnets available, you must find the difference of bits between the larger mask and the smaller mask. The formula used for calculating number of subnets is: 2n2n2n2n n = number of bits difference If given a /20 network, how many /24 networks can we get out of it? 2 4 = 16

Finding valid network id’s To find valid network id’s, you must first know the network id of your large network. Next, you need to know what size networks you would like to subnet to. Find the number of smaller networks you will have. (2 n ) Find the value of the last bit of the smaller subnet mask. This will be the increments to count by to find valid network id’s. Continue counting by that number until you reach the last network id.

Subnetting Example You have been assigned /20 How many /23 networks can you create? 2 (23-20) 2 (23-20) = = 8 networks What are their network id’s? Find the least significant bit position for / Count in increments of , , , , , , , , , , , , ,

Variable Length Subnet Masks VLSM simply means that your smaller networks do not have to be the same size. Example: If you have been provided a /22, you can subnet one /23 and two /24 networks.

VLSM Example A /21 network could be subnetted as follows: /22 /22 /22 /22 /23 /23 /23 /23 /24 /24 /24 /24 /25 /25 /25 /25 /26 /26 /26 /26 /27 /27 /27 /27 /28 /28 /28 /28 /29 /29 /29 /29 /30 /30 /30 /30 /27 /27 /27 /27 /30 /30 /30 /30

Questions or Comments? Adam Vocks - MCP, MCSE Vice-President Computer Techniques, Inc.