CIDR Practice Question

Duration: 8 min

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Inside: a video lesson and guided study material.

Module outline

  1. Paper 1 | Reasoning Test: Series (Number and Letter Series) (Numerical Relations and Reasoning), Coding Decoding, Data Sufficiency, Syllogisms, Deductive and Inductive Reasoning (Logical Deduction and Induction) (Prepositional Reasoning), Seating Arrangements, Blood Relations, Puzzle Solving (Puzzles), Venn Diagram, Analogy, Ranking, Order and Sequence, Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning), Selection Decision Table (Decision Making), Logical Sequence Of Words, Cubes & Dices, Analytical Reasoning (Counting Figures Reasoning), Calendar, Alphabet and Word Tests, Numerical Reasoning, Number System, Averages, Mixtures and Alligation, Percentages, Series Completion, Analogy and Classification, Patterns in Two-Dimensional Figures, Coding and Decoding, Mathematical Operations, Direction Sense, Algebra, Logical Deduction and Induction, Syllogisms and Venn Diagrams, Critical Reasoning, Order, Ranking and Sequence, Reading Comprehension, Profit, Loss and Discount, Constraint Puzzles, Speed, Time and Distance, Traverse Surveying, Ratio and Proportion, Time and Work, Mensuration, Permutations and Combinations, Clocks and Calendars, Data Interpretation, Assembling and Grouping of Shapes, Transformation of Shapes, Three-Dimensional Patterns and Visualization, Cubes and Dice, Vocabulary, Blood Relations, Data Sufficiency
  2. Paper 1 | Numerical Analysis: Number System, HCF LCM, Percentage, Ratio and Proportion (Ratios), Average, Sequence and Series (Series), Powers and Exponents (Surds and Indices), Algebra, Statistics, Data Interpretation, Mental Ability, Arithmetic, Logarithm, Profit and Loss, Simple Interest and Compound Interest, Speed Time and Distance, Mixture and Alligation, Mensuration and Geometry, Permutation and Combination, Probability, Sequences and Series, Powers, Surds and Logarithms, Subject-Verb Agreement, Sentence Completion, Geometry, Sentence Structure and Correction, Data Sufficiency, Trigonometry, Measurement and Quantity Take-Off, Signal Space and Optimum Detection, Probability, Statistics, Algebra, Time and Work, Speed, Time and Distance, Data Interpretation, Graph Theory, Combinatorics
  3. Paper 1 | General Knowledge: State Wise GK, History, Geography, GK- Current Affairs, Static General Knowledge, Polity, Indian Economy
  4. Paper 1 | DBMS: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, File Organization & Indexing, Relational Algebra, SQL, Transaction Management, Concurrency Control, Relational Calculus, Database Security & Authorization, Database Recovery
  5. Paper 1 | Data Communication & Network: Introduction to CN, Data Communication, DLL: Access Control, DLL: Flow Control, DLL: Error Control, DLL: Framing, Data Link Layer - Ethernet, Net Layer: IPv4 & Proto, Net Layer: IP Addressing, Net Layer:Routing Protocol, Transport Layer Services, TL: Congestion & UDP, Application Layer, Network Security, Security in Mobile and Wireless Computing, Input Output Organisation, File Management, Hardware Basics, Terms & Abbreviations, Protocols & Services, Network Access Technologies, Cyber Safety and Security, Basics of COA
  6. Paper 2 | System Analysis & Design: Fundamentals of Systems and Information Systems, SDLC and Development Approaches, Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Documentation and Software Requirements Specification (SRS), SDD and Quality Assurance, Software Design, Estimation and Metrics, Software Testing, Software Maintenance and Configuration Management, Security, Risk Management & Maintenance, extras
  7. Paper 2 | Programming Language (Java): Java Fundamentals, OOPS with Java, Array, String, IO & References, Generic & Collections, Multithreading, Java, Miscellaneous, Control Flow, OOPS with C++, Stack, C Fundamentals, Arrays & Pointers, Object Oriented Technology, Control Flow & Looping, Introduction to Python
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This educational video provides a step-by-step guide to Variable Length Subnet Masking (VLSM) using a specific networking problem. The instructor starts with a single Class C network, 200.1.2.0/24, and demonstrates how to divide it into three distinct subnets with varying host requirements: one subnet needing 126 hosts and two others needing 62 hosts each. The lecture emphasizes the importance of allocating the largest subnet first to prevent address fragmentation. Through a combination of whiteboard drawing and slide presentation, the instructor derives the correct subnet masks (/25 and /26) and calculates the precise IP address ranges for each resulting subnet, concluding with a summary of CIDR formulas.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The video begins with the instructor presenting a specific problem statement on the screen: "Consider we have a big single network having IP Address 200.1.2.0/24. We want to do subnetting and divide this network into 3 subnets, such that first contains 126 hosts, and other two contains 62 hosts each?" He starts the solution by writing the network address 200.1.2.0/24 at the top of the screen. He then draws a large blue circle to represent the entire available IP address space. To the left of the circle, he writes the number "3" in a red circle, indicating the three subnets required. He proceeds to draw a vertical red line down the center of the blue circle, effectively splitting the address space into two equal halves, which is the first step in allocating the largest subnet.

  2. 2:00 – 5:00 02:00-05:00

    The instructor focuses on the first requirement: a subnet with 126 hosts. He explains that to support 126 usable hosts, the subnet must have a block size of 128 (2^7), because 2^7 - 2 = 126. This means 7 bits are needed for hosts, leaving 25 bits for the network prefix (32 - 7 = 25). He writes /25 next to the left half of the circle. Next, he addresses the remaining right half of the circle, which needs to be split into two subnets of 62 hosts each. For 62 hosts, he calculates a block size of 64 (2^6), requiring 6 host bits and a prefix length of 26 (32 - 6 = 26). He draws a horizontal line to split the right side into two quadrants and writes "62" in each. He then writes the specific subnet IDs on the right: 200.1.2.128/26 and 200.1.2.192/26, explaining the binary values 10000000 (128) and 11000000 (192) that determine these starting addresses.

  3. 5:00 – 7:43 05:00-07:43

    The instructor transitions to a slide that summarizes the final calculated subnets. The slide is divided into three sections: "1st Subnet", "2nd Subnet", and "3rd Subnet". For the 1st Subnet, it lists the IP Address as 200.1.2.0, Direct Broadcast Address as 200.1.2.127, and the Range of IP Addresses as [200.1.2.0, 200.1.2.127]. The 2nd Subnet is listed as 200.1.2.128/26 with a range of [200.1.2.128, 200.1.2.191]. The 3rd Subnet is 200.1.2.192/26 with a range of [200.1.2.192, 200.1.2.255]. Finally, a slide titled "Designing subnets for CIDR Notations" appears, showing the formula n_sub = 32 - log_2 N_sub and stating the rule that the starting address must be divisible by the number of addresses in the sub-network.

The lecture successfully bridges the gap between theoretical subnetting rules and practical application. By visually splitting the address space circle, the instructor makes the abstract concept of binary division concrete. The progression from identifying the largest host requirement to calculating the corresponding prefix length and finally listing the specific IP ranges provides a clear, repeatable method for solving VLSM problems. The inclusion of the CIDR formula slide at the end reinforces the mathematical foundation behind the visual steps, ensuring students understand both the "how" and the "why" of the subnetting process.

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