Determine a node’s IP Network Address Gina Minks EME5603 Fall 2008 Final Project For EMC Employees

Introduction In a large IP environment, routers are used to break up large networks into subnetworks. This diagram shows a router breaking a network into three subnets; one for engineering, one for QA, an one for sales. Each node in a network is identified by an IP address and a subnet mask. These two pieces of information can be used to identify on which subnet the node resides. Being able to identify the network information helps make routing between networks efficient. Engineering Sales QA Interne t

Why take this module? By the end of this module, you will be able to take any IP Address and Subnet mask, and using only a pencil and piece of paper determine the network address for that pair. If you work with any of the Network Management/Configuration products you will need to be familiar with basic network troubleshooting skills. If you work with any products that are connected to an IP network, you probably need to know how to troubleshoot that IP connection.

Objectives Given an IP Address, convert the IP address from Decimal to Binary Given a Subnet Mask, convert the Subnet Mask from Decimal to Binary Perform a Boolean AND operation on the Binary IP Address and Binary Subnet Mask Given the result of a Boolean operation on an IP Address and Subnet Mask, convert the binary operation results to decimal format Write the Network Address for the given IP Address and Subnet Mask in dotted decimal notation These are the steps used to find the network address from the IP Address and the Subnet Mask. We’ll go over each of these steps in detail in upcoming pages.

Review of terms Before we get started, let’s go over a few terms you will need to know to complete this module. 1.Octet: 8 consecutive bits, or one byte. IP addresses have 4 octets 2.MSD: Most Significant Digit This is the left most digit, or the digit with the greatest value in the number 3.LSD: Least Significant Digit This is the right-most digit, or the digit with the least value in the number 4.Dotted Decimal Notation: IP addresses are written in decimal format so that they are easier for humans to read. The numbers are the decimal representation of the binary octets. Each octet is separated by a decimal. Now that we’ve reviewed the terminology, let’s get started!

Determining the Network Address Suppose we have the following information about a node on the network: IP Address Subnet Mask How do you figure out the network on which the node resides? Engineering Sales QA

These are all of the steps required to determine the network ID of an IP Address and Subnet Mask: Separate the IP address & Subnet Mask into octets Convert each octet from decimal to binary Perform an AND on the IP address & Subnet Mask convert the result of step three from binary to decimal Write the converted number in dotted decimal notation. This is the network IP Address: Steps to find the network ID Subnet Mask255 0 IP Address Subnet Mask IP Address Subnet Mask IP Address AND AND

Hang in there… We’ll go through this step by step Don’t freak out yet!

Step 1: Separate the IP address & Subnet Mask into octets Both the IP Address and the Subnet mask must be converted from decimal to binary. This will be easier if you work on one address and one octet at a time For the example we’ll work through in this module, we’ll use the following node information: IP Address: Subnet Mask: Network Address: ____________ Let’s start by separating the IP address into octets. Can you list the four octets of this IP Address?

Did you list the following as the octets? Fantastic! Each octet of the IP address and Subnet Mask must be converted from decimal format to binary format. To make things easy at first, fill out this chart as you complete the conversion. Separate the IP address & Subnet Mask into octets Decimal Binary

Step Two: Convert each octet to binary Let’s review the steps to convert a decimal number to binary, and then you can practice performing a few conversions on your own First, we’ll review the rules we need to follow.

Rules for converting decimal to binary Evaluate the number, beginning with the MSB The number is > 128The number is = 128The number is < Write a 1 in the binary conversion chart column 1. Write a 0 in the binary conversion chart column 2. Subtract 128 from the number 2. Write a 0 in each remaining conversion chart column 2. Evaluate the number with the next place value in the conversion chart 3. Evaluate the difference with the next place value in the conversion chart 3. Write each number in the conversion chart out – this is the binary number 3. Continue until the LSB has been evaluated 4. Write each number in the conversion chart out – this is the binary number

Examples for the 128 column Let’s continue to evaluate the IP address. Start with the right-most octet (219) 219 is MORE THAN 128 Place a 1 in the MSB column of the binary conversion chart Place Value 1? Binary Place Value 1 Binary Subtract 128 from 219: Evaluate 91 with the next place value (64) YOU TRY IT: Do you put a 1 or a 0 in the 64 place value column?

ANSWER Place Value 11 Binary 91 is GREATER THAN 64, so a 1 goes in the 64 place value column YOU TRY IT: What do you do next?

Next step -- That’s right! Subtract 64 from 91: And then evaluate 27 with the next place value (32). YOU TRY IT: What number goes in the 32 place value column? Place Value 11? Binary

ANSWER Place Value 110 Binary 27 is LESS THAN 32, so a 0 goes in the 32 place value column You are doing great! Keep going! YOU TRY IT: What do you do next?

Next step -- That’s right! Evaluate 27 with the next place value (16). YOU TRY IT: What number goes in the 16 place value column? Place Value 110? Binary

ANSWER Place Value 1101 Binary 27 is MORE THAN 16, so a 1 goes in the 16 place value column You are doing great! Keep going! YOU TRY IT: What do you do next?

Next step -- That’s right! Subtract 16 from 27: Now evaluate 11 with the next Place Value column (8). YOU TRY IT: What number goes in the 8 place value column? Place Value 1101? Binary

ANSWER Place Value Binary 11 is MORE THAN 8, so a 1 goes in the 8 place value column You are doing great! Keep going! YOU TRY IT: What do you do next?

Next step -- That’s right! Subtract 8 from 11: Now evaluate 3 with the next Place Value column (4). YOU TRY IT: What number goes in the 4 place value column? Place Value 11101? Binary

ANSWER Place Value Binary 3 is LESS THAN 4, so a 0 goes in the 4 place value column You are doing great! Keep going! YOU TRY IT: What do you do next?

Next step -- That’s right! Evaluate 3 with the next Place Value column (2). YOU TRY IT: What number goes in the 2 place value column? Place Value ? Binary

Next step Place Value ? Binary Correct! A 1 goes in the 2 Place Value column because 3 is GREATER THAN 2. Next, Subtract 3 from 2: Finally, evaluate 1 with the next Place Value column (1). Does a 1 or a 0 go in the 1 Place Value column?

Final Answer Place Value Binary Correct! A 1 goes in the 1 Place Value column because 1 is EQUAL TO 1 You’re Done! Now just write the digits from each of the columns, beginning with the MSB: is the binary equivalent of 219

So we have converted one octet of the given IP address to binary. Write it in the chart Separate the IP address & Subnet Mask into octets Decimal Binary We still have to convert the other three octets of this IP address to binary. Not to mention, we still have to do the conversion on the Subnet mask. Let’s get started!

Do the conversion Now you do the conversion for the other octets in the IP address Don’t cheat and use the calculator! Work out the conversion using the binary conversion chart. Refer to pages 13 – 26 if you get stuck Place Value Binary Place Value Binary Place Value Binary

Conversion Answers Now check your work. Did come up with the following binary values for each octet? Place Value Binary Place Value Binary Place Value Binary

Awesome! Now record the binary value of each octet in the Write it in the chart Record Binary values for each octet Decimal Binary Now we have the binary representation of the given IP address. Now it’s time to do more decimal to binary conversion. We need to convert the subnet mask from decimal to binary as well. Do you remember the first step?

If you chose separate the Subnet Mask into octets, that is correct. If you recall, the given Subnet Mask for our module is Fill out this chart, separating the octets of the Subnet Mask into the four columns of the Decimal row. Separate Subnet Mask into octets ???? Decimal Binary

This chart shows the correct separation of the octets in the Subnet Mask. Did you get it right? Octet Separation Answer Decimal Binary Do you remember the next step?

Convert the subnet mask to binary That’s right – do the binary to decimal conversion. There are only two numbers to convert: 0 and 255. Now you do the conversion for the other octets in the IP address Don’t cheat and use the calculator! Work out the conversion using the binary conversion chart. Refer to pages 13 – 26 if you get stuck Place Value Binary Place Value Binary

Do the conversion Did you get these values when you did the conversion? Great. Now, fill out the octet chart Place Value Binary Place Value Binary

This chart shows the correct separation of the octets in the Subnet Mask. Did you get perform the conversion correctly? Answer Decimal Binary Ok so let’s review where we are so far….

√ Separate the IP address & Subnet Mask into octets First step, complete Subnet Mask255 0 IP Address

√ Separate the IP address & Subnet Mask into octets √ Convert each octet from decimal to binary Second Step, complete Subnet Mask255 0 IP Address Subnet Mask IP Address

√ Separate the IP address & Subnet Mask into octets √ Convert each octet from decimal to binary → Perform an AND on the IP address & Subnet Mask Step Three: Perform an AND Operation Subnet Mask255 0 IP Address Subnet Mask IP Address Subnet Mask IP Address AND Perform an AND? What does THAT mean?

Boolean AND rules Boolean is a type of math. A Boolean AND is a mathematical operation that takes two binary numbers and combines them into one number. Here are the rules to the Boolean AND operation: = = = = 1 For example, to AND the following binary numbers: You would perform the Boolean operation on each pair of numbers, starting with the LSD: Or:

Let’s try an example. What is the result of the Boolean AND of the following binary numbers? Remember: Perform the Boolean operation on each pair of numbers, starting with the LSD Boolean AND practice

Boolean AND answer Is this the answer you got? Great! Now perform an AND operation on the binary version of the IP and Subnet Mask we have been evaluating during this module: Subnet Mask IP Address AND

Boolean AND answer Is this the answer you got? Fantastic! Now it’s time to move to the next step. Subnet Mask IP Address AND

Let’s review the steps we’ve completed so far: √ Separate the IP address & Subnet Mask into octets √ Convert each octet from decimal to binary √ Perform an AND on the IP address & Subnet Mask That means we are almost done! → Convert the result of the AND operation from binary to decimal Steps to find the network ID Subnet Mask255 0 IP Address Subnet Mask IP Address Subnet Mask IP Address AND AND????

We’ll use the binary conversion chart to convert a binary number to decimal. In the chart, write the place value for the column under every one in the binary number. Next, add up all the numbers in the Decimal Row = 166 Write the sum of the numbers in the Decimal Row in the Decimal Value Row. This is the decimal equivalent of the binary number Rules for converting from binary to decimal Place Value Binary Decimal Decimal Value Place Value Binary Decimal 166Decimal Value

Step 4: Convert the AND result from Binary to Decimal AND Place Value Binary Decimal Decimal Value Place Value Binary Decimal Decimal Value Now it’s your turn! Convert each section of the AND result from Binary to decimal Place Value Binary Decimal Decimal Value Place Value Binary Decimal Decimal Value

Results AND Place Value Binary 82Decimal 10Decimal Value Place Value Binary Decimal 127Decimal Value Did you get the same results? Place Value Binary 6432Decimal 96Decimal Value Place Value Binary Decimal 0Decimal Value

Let’s review the steps we’ve completed so far: √ Separate the IP address & Subnet Mask into octets √ Convert each octet from decimal to binary √ Perform an AND on the IP address & Subnet Mask √ Convert the result of the AND operation from binary to decimal There is only one more step! → Write the converted number in dotted decimal notation. Steps to find the network ID Subnet Mask255 0 IP Address Subnet Mask IP Address Subnet Mask IP Address AND AND

Step 5: Write the converted number in dotted decimal notation This step is straight forward. Write the converted value of the AND operation in dotted decimal format. Network Address = AND

Final Practice We’ve practiced the individual steps needed to find the Network Address from an IP Address and Subnet Mask. Now you get to practice doing the entire thing on your own. Using the following IP Address and Subnet Mask, determine the pair’s Network Address. Feel free to use any of the aides in this lesson, but do not use a calculator! IP Address: Subnet Mask: Network Address:________________

Final Answer Did you get the correct answer? IP Address: Subnet Mask: Network Address: Fantastic!! Now please proceed to the Post-Test to see if you are ready to proceed to the next level in the world of networking.