CCNA | Subnetting (Part 1) | Day 13 |
Introduction to Subnetting
Welcome to Jeremy's IT Lab, a free CCNA course.
Importance of subnetting in networking.
Aim to simplify the concept of subnetting.
Video segmented into two or three parts for better understanding.
CIDR (Classless Interdomain Routing)
CIDR stands for Classless Inter-Domain Routing.
Developed to increase flexibility in IPv4 addressing.
Moves away from rigid Class A, B, C addressing.
Overview of IPv4 Address Classes
Five classes of IPv4 addresses: A, B, C, D, E.
Class A
Begins with 0 in the first octet.
Decimal range: 0 to 127.
IP Address Range: 0.0.0.0 to 127.255.255.255.
Prefix Length: /8 (first octet for network, 3 for hosts).
Large usable address space: ~16,777,216 addresses.
Class B
Begins with 10 in the first octet.
Decimal range: 128 to 191.
IP Address Range: 128.0.0.0 to 191.255.255.255.
Prefix Length: /16 (first two octets for network, 2 for hosts).
Usable addresses: ~65,536.
Class C
Begins with 110 in the first three bits.
Decimal range: 192 to 223.
IP Address Range: 192.0.0.0 to 223.255.255.255.
Prefix Length: /24 (first three octets for network, last one for hosts).
Usable addresses: 256.
Class D
Begins with 1110 (used for multicast).
Decimal range: 224 to 239.
Class E
Begins with 1111 (reserved for future use).
Decimal range: 240 to 255.
Issues with Classful Addressing
Classful addressing can lead to wasted IP addresses.
Example of point-to-point connection leads to underutilization.
Companies assigned network ranges based on size (Class A for large, Class C for small).
Transition to CIDR
Introduced by the IETF in 1993.
Removes strict class rules, allows for variable-length subnet masking.
Improves efficiency in allocation.
Example of Subnetting
Re-evaluating a point-to-point network using CIDR.
Addresses can be assigned in smaller blocks according to requirements.
Calculating Usable Addresses
Formula for usable addresses: 2^n - 2, where n = number of host bits.
CIDR Notation and Subnet Masks
CIDR uses a slash (/) notation to denote prefix length.
Example: /24 corresponds to 255.255.255.0.
Practice Calculation Tasks
Example with 203.0.113.0 network to illustrate usable addresses for different prefix lengths:
/24: 254 usable addresses.
/25: 126 usable addresses.
/26: 62 usable addresses.
/27: 30 usable addresses.
/28: 14 usable addresses.
/29: 6 usable addresses.
/30: 2 usable addresses (4 total).
/31: 0 usable addresses, but usable for point-to-point links.
/32: Not really usable for general networking but can specify one host.
Characteristics of 31 and 32 Networks
Using /31 allows addressing two routers directly.
/32 is generally used in static configurations for specific hosts.
Summary of Key Points
CIDR provides flexibility over traditional classful addressing.
Understanding how to subnet efficiently saves IP addresses and optimizes network usage.
Upcoming Content
Next video will cover practice problems and provide practical exercises on subnetting.
A final task mentioned to find subnets for a network with specific requirements.
Calls to Action
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Offer links for supplementary materials (flashcards).
Membership options available for further support.