ClassLess Interdomain Routing - CIDR With Example

Duration: 4 min

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Module outline

  1. Quantitative Aptitude: Ratio and Proportion (Ratios), Data Interpretation, Mixture and Alligation, Permutation and Combination, Number System, Sequence and Series (Series), Speed Time and Distance, Speed Mathematics and Basic Mathematics, Algebra, Percentage, Profit and Loss, Simple Interest and Compound Interest, Powers and Exponents (Surds and Indices), Time and Work, Mensuration and Geometry, Partnership
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  3. English Language: Vocabulary, Noun, Subject Verb Agreement (Verb Noun Agreement), Adjectives, Tenses, Comprehension / Reading Comprehension / Unseen Passages (Critical Reasoning) (Paragraph Questions), Cloze Test (Cloze Passage), Sentence Correction (Error Correction), Sentence Completion (Fill in the blanks), Sentence Re-arrangements (Para Jumbles) (Narrative Sequencing), Sentence Construction, Pronoun, Preposition, Conjunction, Adverb, Verb, Modals, Articles, Determiner, Interjection
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  10. SQL (IT Specialist): SQL
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  15. Computer Architecture (IT Specialist): Basics of COA, Floating Point Rep, Cache Memory Organization, Input Output Organisation, Pipelining, Instr Formats & Modes, Control Unit Design, Register Transfer and Microoperations, Multiprocessors, Programming the Basic Computer
  16. Data Communication & Networking (IT Specialist): 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
  17. Descriptive Test (Main Exam): English Writing Ability
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This lecture segment teaches how to determine the number of addresses, first address, and last address for a CIDR block using an address mask. The instructor works through the example 167.199.170.82/27, showing its binary form 10100111 11000111 10101010 01010010. The mask is formed by setting the 27 leftmost bits to 1 and the remaining 5 bits to 0. The number of addresses is calculated as N = NOT(mask) + 1, which equals 2^5 = 32. The first address is found by ANDing the given address with the mask, yielding 167.199.170.64. The last address is found by ORing the given address with NOT(mask), yielding 167.199.170.95. A summary slide titled “Address Mask” defines the mask as a 32-bit number with n leftmost bits set to 1 and the rest 0, and lists the three bitwise operations NOT, AND, and OR used to compute block properties.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The slide presents the question “Find the Number of addresses, first and last address of the CIDR block to which” with “Address: 167.199.170.82/27 (10100111 11000111 10101010 01010010) belongs to.” The instructor circles the address line and underlines binary octets, isolating the final group “01010010.” He then writes “2^5 = 32” on the whiteboard, indicating that with a /27 prefix there are 5 host bits and therefore 32 addresses in the block.

  2. 2:00 – 4:15 02:00-04:15

    A second slide states “The mask by setting 27 leftmost bits to 1 and 5 rightmost bits to 0 in dotted-decimal notation is:” and “Number of addresses in the block: N = NOT (mask) + 1 =”, with “NOT” circled in red. The instructor sketches tally marks and five circles representing the zero bits. Later slides show “First address: First = (address) AND (mask) =” and “Last address: Last = (address) OR (NOT mask) =”, with binary rows for the AND and OR operations. The computed first address 167.199.170.64 and last address 167.199.170.95 appear on screen. A final “Address Mask” slide defines the mask as a 32-bit number with n leftmost bits set to 1 and lists N = NOT(mask) + 1, first address = (any address in block) AND mask, and last address = (any address in block) OR NOT(mask).

The lesson centers on CIDR address-mask arithmetic. The key rule is that a /n prefix creates a mask with n leading 1-bits and (32-n) trailing 0-bits. From this mask, three bitwise formulas give block properties: N = NOT(mask) + 1 for the number of addresses, first address = address AND mask, and last address = address OR NOT(mask). In the worked example 167.199.170.82/27, the five trailing zero bits give 2^5 = 32 addresses. ANDing with the mask clears host bits to produce the first address 167.199.170.64, while ORing with NOT(mask) sets host bits to 1 to produce the last address 167.199.170.95. The progression moves from identifying the prefix length, to constructing the mask, to applying NOT/AND/OR operations, and finally to a summary slide that generalizes the method.

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