CIDR block representation practice question
Duration: 4 min
This video lesson is available to enrolled students.
Inside: a video lesson and guided study material.
Module outline
- Quantitative Ability: Percentage, Profit and Loss, Ratio and Proportion (Ratios), Average, Time and Work, Speed Time and Distance, Simple Interest and Compound Interest, Age Problems, Number System, Divisibility Rules, HCF LCM, Algebra, Permutation and Combination, Probability, Data Interpretation, Logarithm, Sequence and Series (Series), Powers and Exponents (Surds and Indices), Speed Mathematics and Basic Mathematics
- Logical Reasoning: Seating Arrangements, Puzzle Solving (Puzzles), Data Arrangement, Coding Decoding, Blood Relations, Directions (Direction Test), Ranking, Order and Sequence, Data Sufficiency, Venn Diagram, Inequality, Series (Number and Letter Series) (Numerical Relations and Reasoning), Logical Sequence Of Words, Deductive and Inductive Reasoning (Logical Deduction and Induction) (Prepositional Reasoning), Selection Decision Table (Decision Making), Analogy, Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning)
- Verbal Ability: Comprehension / Reading Comprehension / Unseen Passages (Critical Reasoning) (Paragraph Questions), Subject Verb Agreement (Verb Noun Agreement), Tenses, Articles, Preposition, Conjunction, Modals, Active Passive Voice (Voice), Direct and Indirect Speech, Vocabulary, Sentence Re-arrangements (Para Jumbles) (Narrative Sequencing), Sentence Completion (Fill in the blanks), Sentence Correction (Error Correction), Cloze Test (Cloze Passage), Facts, Inference and Judgements
- Programming Fundamentals (Technical): C Fundamentals
- Data Structures (Technical): Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing
- Algorithms (Technical): Algorithm Analysis, Sorting Algorithms, Greedy Algorithms, Dynamic Programming, Minimum Spanning Trees, Shortest Path Algos, Time Complexity Analysis, Advanced Algorithms
- OOPs (Technical): Object Oriented Programming (OOPS)
- DBMS (Technical): Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, File Organization & Indexing, Relational Algebra, Relational Calculus, Transaction Management, Concurrency Control, Database Recovery, ORDBMS, Database Security & Authorization, Query Processing & Optimization, Enhanced Data Models, Data Warehousing & Mining, Big Data Systems, NoSQL
- SQL (Technical): SQL
- Operating Systems (Technical): Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Deadlock, Threads & Process Creation, Memory Management, Virtual Memory, Disc Scheduling, File Management, Windows OS, Linux OS, Security, Distributed Systems, Virtual Machines
- Computer Networks (Technical): 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, Cloud Computing and IoT, Cyber and Info Security
- Software Engineering (Technical): Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Design, Estimation and Metrics, Software Testing, Software Maintenance and Configuration Management
- Coding/Automata Round: Coding Questions by Yash Sir, C Programming by Yash Sir, Programming in C++, Java, Python for Placements by Yash Sir, Pseudo Codes
- Personality / Behavioral Assessment: Behavioral Assessment (Behavioral Competency Profiling) (Psychometric Test)
- Writing Assessment: English Writing Ability
AI summary & chapters
AI Summary
An AI-generated summary of this video lecture.
The video lecture focuses on determining if a specific range of IP addresses constitutes a valid Classless Inter-Domain Routing (CIDR) block and finding its representation. The instructor presents a problem involving the range 100.1.2.32 to 100.1.2.47. He systematically applies three rules: contiguity, power-of-2 size, and divisibility of the first address. Through step-by-step calculation, he verifies the block size is 16, confirms it is a power of 2, and checks if the starting address is divisible by 16. Finally, he derives the CIDR notation /28. The lecture is structured around a specific question displayed on the slide, guiding the student through the verification process.
Chapters
0:00 – 2:00 00:00-02:00
The instructor introduces the problem statement displayed on screen: "Consider a block of IP Addresses ranging from 100.1.2.32 to 100.1.2.47." He underlines the question "Is it a CIDR block?" and lists the "Rules for Creating CIDR Block (Network)". He begins calculating the total number of addresses by subtracting the start from the end: "47 - 32". He emphasizes the need to add 1 for inclusive counting, writing "(47 - 32) + 1". He explains the "plus 1" concept using a small example "0-9" resulting in 10 numbers. He calculates the total size as 16. He writes "15 + 1" and circles "16". He also writes "35" and "35" vertically, seemingly checking something else or just scribbling, but focuses on the 16.
2:00 – 3:38 02:00-03:38
The instructor verifies the calculated size of 16 against the rules. He checks if 16 is a power of 2, noting the sequence "8, 16, 32, 64, 128" written on the board. He then applies the third rule: "First IP Address of the block must be divisible by the size of the block." He writes "32 / 16" and confirms the result is 2, meaning it divides evenly. He concludes it is a valid CIDR block. He then determines the CIDR representation. Since the block size is 16 ($2^4$), he deduces the host bits are 4. He calculates the network prefix as $32 - 4 = 28$. He writes the final answer "100.1.2.32 / 28". He also draws a diagram of 32 bits to visualize the host bits.
The lesson effectively demonstrates the algorithmic approach to validating CIDR blocks. By breaking down the problem into size calculation, power-of-2 verification, and divisibility checks, the instructor provides a clear method for students to solve similar networking problems. The final derivation of the /28 prefix solidifies the connection between block size and CIDR notation. The visual aids, such as the list of powers of 2 and the divisibility check, reinforce the theoretical rules with practical application.

