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April 19, 2023 RE Meyers, Ms.Ed., CCAI
CCENT Exam Success StrategiesCCENT Exam Success Strategies
Accurate and Fast IP Address Problem Solving
Part 1: Building A Subnet Answer Key
April 19, 2023 RE Meyers, Ms.Ed., CCAI
ObjectiveObjective
After successfully completing the activities in this presentation, the student will be able to construct an IP Addressing “answer key” for 2 octets with no outside assistance that includes:
• CIDR• Subnet mask values• Powers of two and their equivalent values• Binary value for each bit of each octet
April 19, 2023 RE Meyers, Ms.Ed., CCAI
Subnets and VLSM Problem SolvingSubnets and VLSM Problem Solving
Given enough practice and time, networking instructors and students will be able to solve all subnet and VLSM problems on an exam.On a certification exam, the biggest challenge is time.
• Certification exam time management is a critical skill for success.• Spend the least amount of time on each question.• Under pressure of a ticking clock, anyone can choke and freeze.• Accurate answers can be found quickly!• It requires patience and practice.• Did I mention practice? You must practice. A lot.
April 19, 2023 RE Meyers, Ms.Ed., CCAI
IP Address Problem SolvingIP Address Problem Solving
“What do I need to know first?”You must be 100% locked in
converting decimal numbers 0 – 255 to binary, and eight bit binary to decimal accurately and quickly.
If not, then this presentation will not help much.
Practice binary-decimal-binary conversions until you can do them easily.
April 19, 2023 RE Meyers, Ms.Ed., CCAI
Subnets and VLSM Problem SolvingSubnets and VLSM Problem Solving
What else do I need to know?” This is not a presentation on how to subnet or how to
develop VLSM IP addresses.Both of those skills are presumed to be taught, practiced,
and accomplished already.Practice is the only way to become proficient at
subnetting and VLSM addressing. • Very few people actually like to practice.• Nobody likes to fail.• Practice reduces failure to a small percentage.• Your choice.
April 19, 2023 RE Meyers, Ms.Ed., CCAI
Critical ReadingCritical Reading
Many complain that Cisco exams are “reading comprehension exams” and not technical exams.Anyone who works at a help desk will confirm that clear
communication is the first hurdle to solving any problem.This presentation will focus on getting the correct
addresses. Part 3 is about picking out the words that are important, and those that are not.
April 19, 2023 RE Meyers, Ms.Ed., CCAI
IP Problem Solving: IP Problem Solving: Use the Answer KeyUse the Answer Key
Every certification exam allows you to write notes using given pen and paper.Usually these are a erasable pen and
an 8”x10” piece of laminated paper or card stock.
Before you start the exam, and the ticking clock, create your IP Addressing Answer Key.
The exam problems will then be easy to solve.
April 19, 2023 RE Meyers, Ms.Ed., CCAI
Building the Subnet the Answer KeyBuilding the Subnet the Answer Key
Watch this presentation once or twice without writing anything down.Then click through it while doing all the steps on paper.You’ll be tempted to just print it the key. Don’t!The point is to be able to write the key out during a
certification exam. • You don’t get to bring a pre-printed key in with you!
If you can’t create it from a blank page, then you are no better off than before.
April 19, 2023 RE Meyers, Ms.Ed., CCAI
Building an the Subnet Answer Key: Step 1Building an the Subnet Answer Key: Step 1
1. Take your paper and set it long ways (landscape) on the table. At an inch down from the top, draw a dotted line to the
bottom, and put a big dot at the top of it.
April 19, 2023 RE Meyers, Ms.Ed., CCAI
Building an the Subnet Answer Key: Step 2Building an the Subnet Answer Key: Step 2
2. Using the width of a finger, draw 8 lines down on EACH side of the center dotted line Each column, between the lines, is one of eight binary
bits to the right of the dot, and eight bits to the left.
April 19, 2023 RE Meyers, Ms.Ed., CCAI
Building an the Subnet Answer Key: Step 3Building an the Subnet Answer Key: Step 3
3. At the top of the center line dot, write /24. This dot is the divider between the octet on the right and
the octet on the left. The right is the fourth octet of an IP address The left is the third octet of an IP address /24 is the CIDR notation for the divider between the 3rd
and 4th octet, and the default for a Class C address.
/24
April 19, 2023 RE Meyers, Ms.Ed., CCAI
Building an the Subnet Answer Key: Step 4Building an the Subnet Answer Key: Step 4
4. Complete the rest of the CIDR notations From center to right, add one for each line From center left, subtract one for each line
/24/20 /21 /22 /23 /25 /26 /27 /28 /29 /30/19/18/17 /31/16 /32
April 19, 2023 RE Meyers, Ms.Ed., CCAI
Building an the Subnet Answer Key: Step 5Building an the Subnet Answer Key: Step 5
5. About 11/2 inch down from the CIDR in each binary bit column, write the decimal equivalent of each binary placeholder in each octet. From right to left: 1, 2, 4, 8 …etc. Remember all you
have to do is start from 1 and multiple by 2. Restart after the /24 dot. Then draw a horizontal line under the numbers
4. Complete the rest of the CIDR notations From center to right, add one for each line From center left, subtract one for each line
/24/20 /21 /22 /23 /25 /26 /27 /28 /29 /30/19/18/17 /31/16 /32
128 4 2 1 12481632641288163264
April 19, 2023 RE Meyers, Ms.Ed., CCAI
Building an the Subnet Answer Key: Step 6Building an the Subnet Answer Key: Step 6
6. Right above the decimal placeholder numbers, write the power of 2 numbers. From right to left, 20, 21, 22, etc. all the way to the end on
the left. Do NOT restart at the /24 dot!
5. About 11/2 inch down from the CIDR in each binary bit column, write the decimal equivalent of each binary placeholder in each octet. From right to left: 1, 2, 4, 8 …etc. Remember all you
have to do is start from 1 and multiple by 2. Restart after the /24 dot. Then draw a horizontal line under the numbers
4. Complete the rest of the CIDR notations From center to right, add one for each line From center left, subtract one for each line
/24/20 /21 /22 /23 /25 /26 /27 /28 /29 /30/19/18/17 /31/16 /32
128 4 2 1 12481632641288163264
2023 2125 22242628 2729210211214 212213215
April 19, 2023 RE Meyers, Ms.Ed., CCAI
Building an the Subnet Answer Key: Step 7Building an the Subnet Answer Key: Step 7
7. Above the powers of 2 enter the decimal equivalents of each. Start at the right under 20 with “1” and just multiply by 2
for every bit column as you go to the left.
6. Right above the decimal placeholder numbers, write the power of 2 numbers. From right to left, 20, 21, 22, etc. all the way to the end on
the left. Do NOT restart at the /24 dot!
5. About 11/2 inch down from the CIDR in each binary bit column, write the decimal equivalent of each binary placeholder in each octet. From right to left: 1, 2, 4, 8 …etc. Remember all you
have to do is start from 1 and multiple by 2. Restart after the /24 dot. Then draw a horizontal line under the numbers
4. Complete the rest of the CIDR notations From center to right, add one for each line From center left, subtract one for each line
/24/20 /21 /22 /23 /25 /26 /27 /28 /29 /30/19/18/17 /31/16 /32
128 4 2 1 12481632641288163264
2023 2125 22242628 2729210211214 212213215
124816326412825651210242048409681921638432678
April 19, 2023 RE Meyers, Ms.Ed., CCAI
Building an the Subnet Answer Key: Step 8Building an the Subnet Answer Key: Step 8
8. Last step: Enter the subnet mask numbers for each binary bit column in each octet from left to right. Start with 128 and then add the next column bit value to
get the new entry. Continue left to right and be sure to restart at 128 after
the /24 dot line.
7. Above the powers of 2 enter the decimal powers of 2 numbers Start at the right under 20 with “1” and just multiply by 2
for every bit column as you go to the left.
6. Right above the decimal placeholder numbers, write the power of 2 numbers. From right to left, 20, 21, 22, etc. all the way to the end on
the left. Do NOT restart at the /24 dot!
5. About 11/2 inch down from the CIDR in each binary bit column, write the decimal equivalent of each binary placeholder in each octet. From right to left: 1, 2, 4, 8 …etc. Remember all you
have to do is start from 1 and multiple by 2. Restart after the /24 dot. Then draw a horizontal line under the numbers
4. Complete the rest of the CIDR notations From center to right, add one for each line From center left, subtract one for each line
/24/20 /21 /22 /23 /25 /26 /27 /28 /29 /30/19/18/17 /31/16 /32
128 4 2 1 12481632641288163264
2023 2125 22242628 2729210211214 212213215
124816326412825651210242048409681921638432678
128 192 240224 252248 254 255254252248240224192128255
April 19, 2023 RE Meyers, Ms.Ed., CCAI
Completed Subnet Answer KeyCompleted Subnet Answer Key
Build an answer key in 8 steps. Ironic, eh?7. Above the powers of 2 enter the decimal powers of 2 numbers Start at the right under 20 with “1” and just multiply by 2
for every bit column as you go to the left.
6. Right above the decimal placeholder numbers, write the power of 2 numbers. From right to left, 20, 21, 22, etc. all the way to the end on
the left. Do NOT restart at the /24 dot!
5. About 11/2 inch down from the CIDR in each binary bit column, write the decimal equivalent of each binary placeholder in each octet. From right to left: 1, 2, 4, 8 …etc. Remember all you
have to do is start from 1 and multiple by 2. Restart after the /24 dot. Then draw a horizontal line under the numbers
4. Complete the rest of the CIDR notations From center to right, add one for each line From center left, subtract one for each line
/24/20 /21 /22 /23 /25 /26 /27 /28 /29 /30/19/18/17 /31/16 /32
128 4 2 1 12481632641288163264
2023 2125 22242628 2729210211214 212213215
124816326412825651210242048409681921638432678
128 192 240224 252248 254 255254252248240224192128255
April 19, 2023 RE Meyers, Ms.Ed., CCAI
Review of Each Column and RowReview of Each Column and Row
7. Above the powers of 2 enter the decimal powers of 2 numbers Start at the right under 20 with “1” and just multiply by 2
for every bit column as you go to the left.
6. Right above the decimal placeholder numbers, write the power of 2 numbers. From right to left, 20, 21, 22, etc. all the way to the end on
the left. Do NOT restart at the /24 dot!
5. About 11/2 inch down from the CIDR in each binary bit column, write the decimal equivalent of each binary placeholder in each octet. From right to left: 1, 2, 4, 8 …etc. Remember all you
have to do is start from 1 and multiple by 2. Restart after the /24 dot. Then draw a horizontal line under the numbers
4. Complete the rest of the CIDR notations From center to right, add one for each line From center left, subtract one for each line
/24/20 /21 /22 /23 /25 /26 /27 /28 /29 /30/19/18/17 /31/16 /32
128 4 2 1 12481632641288163264
2023 2125 22242628 2729210211214 212213215
124816326412825651210242048409681921638432678
128 192 240224 252248 254 255254252248240224192128255Top row: CIDR notation for each bit column
Second row down: Normal subnet mask number for each bit columnThird row down: Decimal values for the powers of two for each bit column
Fourth row down: Power of two for each bit column, right to left. Always start with 20 and not 21 !Fifth and last row down: Normal binary bit value for each column
April 19, 2023 RE Meyers, Ms.Ed., CCAI
Now What?Now What?
Did I mention that the only way to solve subnet/VLSM problems quickly and accurately was to practice?First, you need to practice building this key until you can
do it quickly and accurately.The next presentation in this series shows how to use the
answer key to solve subnet problems, followed by VLSM.