Cisco Networking/CCENT/Subnetting

This lesson covers subnetting.

Objectives and Skills
Objectives and skills for the subnetting portion of Cisco CCENT certification include:
 * Identify the appropriate IPv4 addressing scheme using VLSM and summarization to satisfy addressing requirements in a LAN/WAN environment

Readings

 * 1)  Subnetwork
 * 2)  IPv4 subnetting reference
 * 3)  Classless Inter-Domain Routing
 * 4)  Supernetwork
 * 5) Cisco: IP Addressing and Subnetting for New Users

Multimedia

 * 1) YouTube: Binary Math - CompTIA Network+ N10-005: 1.3
 * 2) YouTube:  Subnetting - CompTIA Network+ N10-005: 1.3
 * 3) YouTube: Subnetting, Cisco CCNA, Binary Numbers - Part 1
 * 4) YouTube: Subnetting, Cisco CCNA, Binary Numbers - Part 2
 * 5) YouTube: Subnetting, Cisco CCNA, Binary Numbers - Part 3
 * 6) YouTube: Subnetting, Cisco CCNA, Binary Numbers - Part 4
 * 7) YouTube: Subnetting Cisco CCNA - Part 1 The Magic Number
 * 8) YouTube: Subnetting Cisco CCNA - Part 2 The Magic Number
 * 9) YouTube: Subnetting Cisco CCNA - Part 3 The Magic Number
 * 10) YouTube: Subnetting Cisco CCNA - Part 4 The Magic Number
 * 11) YouTube: Subnetting Cisco CCNA - Part 5 The Magic Number
 * 12) YouTube: Subnetting Cisco CCNA - Part 6 The Magic Number

Activities

 * 1) Review 3com: Understanding IP Addressing: Everything You Ever Wanted To Know.  Complete all exercises in Appendix B (page 57).
 * 2) Review EasySubnetting.com subnetting resources and complete multiple subnetting exercises.
 * 3) Generate practice subnetting questions using the TunnelsUp: Subnet Calculator.
 * 4) Play the Cisco: Subnet Troubleshooting Game and practice until you can consistently achieve a high score.
 * 5) Play the Subnetting.net Subnetting Game and practice until you can consistently achieve a high score.
 * 6) Play the Insite: Cisco Subnet Slingshot Game and practice until you can consistently achieve a high score.
 * 7) Review Subnet Ninja: Subnetting How To Guide and verify your answers with the Subnet Calculator
 * 8) Check your Subnets and Masks Online with this Subnetting Calculator and verify that your subnet masks and CIDR is correct.

Lesson Summary

 * A subnetwork, or subnet, is a logical, visible subdivision of an IP network.
 * The practice of dividing a network into two or more networks is called subnetting.
 * An IP address has two fields, a network prefix and a host identifier.
 * The network prefix is identified using CIDR notation.
 * In IPv4, the network prefix may also be identified using a 32-bit subnet mask in dotted-decimal notation.
 * A network is divided into two or more subnetworks by dividing the host identifier field into separate subnet number and host identifier fields.
 * All hosts on a subnetwork have the same network prefix.
 * Traffic between subnets is exchanged through a router.
 * The first address on any given IPv4 network or subnet is reserved for the network itself.
 * The last address on any given IPv4 network or subnet is reserved for broadcast.
 * The separation of the network prefix/subnet number from the host identifier is performed by a bitwise AND operation between the IP address and the (sub)network mask.
 * The number of subnetworks created by subnetting can be calculated as 2n, where n is the number of bits used for subnetting.
 * The number of available hosts on each subnet can be calculated as 2n-2, where n is the number of bits available for the host identifier.
 * Traditionally, the first network, known as subnet zero, and the last network, known as the all-ones subnet, were not used on production networks. This practice was declared obsolete by  in 1995.
 * The goal of Classless Inter-Domain Routing was to slow the growth of routing tables on routers across the Internet, and to help slow the rapid exhaustion of IPv4 addresses.
 * Classless Inter-Domain Routing is based on variable-length subnet masking (VLSM), which allows a network to be divided into variously sized subnets, providing the opportunity to size a network more appropriately for local needs.
 * The benefits of supernetting are conservation of address space and efficiencies gained in routers in terms of memory storage of route information and processing overhead when matching routes.

Key Terms

 * binary mask
 * Data that is used for bitwise operations to set multiple bits either on, off or inverted in a single bitwise operation.


 * bitwise AND
 * A binary operation that takes two representations of equal length and performs the logical AND operation on each pair of corresponding bits. The result in each position is 1 if the first bit is 1 and the second bit is 1; otherwise, the result is 0.


 * broadcast address
 * A logical address at which all devices connected to a multiple-access communications network are enabled to receive datagrams. In IPv4 networks, the broadcast address is the all-ones address, the last address on the network subnet.


 * network address
 * The address of a network or subnetwork. In IPv4 networks. the network address is the all-zeros address, the first address on the network subnet.


 * prefix mask
 * A subnet mask specified in CIDR notation.


 * provider-independent address space
 * A block of IP addresses assigned by a regional Internet registry (RIR) directly to an end-user organization.


 * routing table
 * A data table stored in a router or a networked computer that lists the routes to particular network destinations, and in some cases, metrics (distances) associated with those routes.


 * subnet
 * A logical, visible subdivision of an IP network.


 * subnet address
 * A logically visible subdivision of an IP network.


 * subnet mask
 * A bitmask that encodes the (sub)network prefix length in dotted-decimal notation, starting with a number of 1 bits equal to the prefix length, ending with 0 bits, and encoded in four-part dotted-decimal format.


 * subnetting
 * The practice of dividing a network into two or more networks.


 * supernet
 * An Internet Protocol (IP) network that is formed from the combination of two or more networks (or subnets) with a common Classless Inter-Domain Routing (CIDR) prefix.


 * variable-length subnet masks (VLSM)
 * Used to divide a network into variously sized subnets, as opposed to fixed-length subnet masks used in classful addressing.

Assessments

 * Flashcards: Quizlet: CCENT - Subnetting
 * Flashcards: Quizlet: Subnet Mask - Mask Bits
 * Flashcards: Quizlet: Subnetting
 * Quiz: Quizlet: CCENT - Subnetting
 * Quiz: Quizlet: Subnet Mask - Mask Bits
 * Quiz: Quizlet: Subnetting