CIDR Practice Question

Duration: 8 min

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Module outline

  1. About Course: About the Course
  2. General Aptitude & Reasoning: Number System, Percentage, Ratio and Proportion (Ratios), Average, Profit and Loss, Simple Interest and Compound Interest, Time and Work, Speed Time and Distance, Mixture and Alligation, Data Interpretation, Algebra, Probability, Permutation and Combination, Venn Diagram, HCF LCM, Divisibility Rules, Age Problems, Pipe and Cistern, Partnership, Linear Algebra, Sequence and Series (Series), Statistics, Powers and Exponents (Surds and Indices), Arithmetic, Mensuration and Geometry, Calculus, Trigonometry, Vectors, Speed Mathematics and Basic Mathematics, Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning), Analogy, Series (Number and Letter Series) (Numerical Relations and Reasoning), Puzzle Solving (Puzzles), Syllogisms, Deductive and Inductive Reasoning (Logical Deduction and Induction) (Prepositional Reasoning), Calendar, Seating Arrangements, Coding Decoding, Blood Relations, Directions (Direction Test), Clock, Analytical Reasoning (Counting Figures Reasoning), Ranking, Order and Sequence, Logical Sequence Of Words, Inequality, Data Sufficiency, Cubes & Dices
  3. Computer Networks & Cybersecurity: 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, Hardware Basics, Network Security
  4. Programming, Data Structures & Algorithms: C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling, OOPS with C++, Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing, Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms, Greedy Algorithms, Dynamic Programming, Minimum Spanning Trees, Shortest Path Algos, Advanced Algorithms
  5. AI, Machine Learning, Big Data & Cloud: Emerging Tech Trends, Artificial Intelligence, Big Data Systems, Approaches to AI, Search Algorithms, Knowledge Representation, Cloud Computing
  6. Digital Logic & Computer Organization: Digital Systems & Boolean Basics, Logic Gates & Hardware, Boolean Expression, Boolean Minimization, Combinational Circuit, Sequential Circuits, Number System, Number Representation, Basics of COA, Floating Point Rep, Cache Memory Organization, Input Output Organisation, Pipelining, Instr Formats & Modes, Register Transfer and Microoperations, Control Unit Design, Programming the Basic Computer
  7. TOC & Compiler: Introduction to TOC, Deterministic FA (DFA), Non-Deterministic FA, Regular Expressions, Grammar, Regular Language Properties, Moore & Mealy Machines, Pushdown Automata & CFG, Turing Machines, Complexity Theory, Intro to Compilers, Lexical Analysis, Grammar & CFG, Syntax Analysis: Top-Down, Syntax Analysis: Bottom-Up, Semantic Analysis & SDT, Intermediate Code Gen, Code Optimization, Run Time Environment
  8. Discrete Mathematics: Set Theory, Relations, Functions, Graph Theory, Group Theory, Propositional and Predicate Logic
  9. Operating System: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Threads & Process Creation, Deadlock, Memory Management, Virtual Memory, Disc Scheduling, File Management, Unix OS, Linux OS, Distributed Systems
  10. Software Engineering: Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Design, Estimation and Metrics, Software Testing, Software Maintenance and Configuration Management, Object Oriented Technology, HTML Basics, JavaScript-Basics, Java, XML
  11. Database Management System: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, File Organization & Indexing, Relational Algebra, SQL, Relational Calculus, Transaction Management, Concurrency Control, Database Recovery, Data Warehousing & Mining, Enhanced Data Models, NoSQL
  12. Other Recurring CS Topics: Basics of Computer Graphics, 2-D Geometrical Transforms and Viewing, Multimedia
  13. Live Classes: ISRO Live classes
  14. Full Mock Test:
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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