Internet Protocol Analysis/Subnetting

This lesson continues the Internet layer and looks at subnetworks, Classless Inter-Domain Routing (CIDR), subnetting, and supernetworks. Activities include IPv4 subnetting, and using the Cisco Subnet Game.

Readings

1. Wikipedia: Subnetwork
2. Wikipedia: IPv4 subnetting reference
3. Wikipedia: CIDR notation
4. Wikipedia: Classless Inter-Domain Routing
5. Wikipedia: Supernetwork

Multimedia

1. YouTube: Subnetting, Cisco CCNA, Binary Numbers - Part 1
2. YouTube: Subnetting, Cisco CCNA, Binary Numbers - Part 2
3. YouTube: Subnetting, Cisco CCNA, Binary Numbers - Part 3
4. YouTube: Subnetting, Cisco CCNA, Binary Numbers - Part 4
5. YouTube: Subnetting Cisco CCNA - Part 1 The Magic Number
6. YouTube: Subnetting Cisco CCNA - Part 2 The Magic Number
7. YouTube: Subnetting Cisco CCNA - Part 3 The Magic Number
8. YouTube: Subnetting Cisco CCNA - Part 4 The Magic Number
9. YouTube: Subnetting Cisco CCNA - Part 5 The Magic Number
10. YouTube: Subnetting Cisco CCNA - Part 6 The Magic Number

Activities

1. Review Cisco: IP Addressing and Subnetting for New Users.
2. Review Understanding TCP/IP addressing and subnetting basics.
3. Experiment with an online subnet calculator such as Online IP Subnet Calculator.
4. Generate practice subnetting questions using this Subnet Calculator.
5. Review EasySubnetting.com subnetting resources.
6. Play the Cisco: Subnet Troubleshooting Game.
7. Consider situations in which a packet analyzer might be used to troubleshoot subnetting and routing traffic.

Lesson Summary

• 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 smaller 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.
• 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

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.

CIDR notation

A compact specification of an Internet Protocol address and its associated routing prefix.

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 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.

Review Questions

Click on a question to see the answer.

1. An IP address has two fields, _____.

   An IP address has two fields, a network prefix and a host identifier.
2. The network prefix is identified using _____.

   The network prefix is identified using CIDR notation.
3. In IPv4, in addition to using CIDR notation, the network prefix may be identified using _____.

   In IPv4, in addition to using CIDR notation, the network prefix may be identified using a 32-bit subnet mask in dotted-decimal notation.
4. A network is divided into two or more subnetworks by dividing _____.

   A network is divided into two or more subnetworks by dividing the host identifier field into separate subnet number and smaller host identifier fields.
5. All hosts on a subnetwork have the same _____.

   All hosts on a subnetwork have the same network prefix.
6. Traffic between subnets is exchanged through a _____.

   Traffic between subnets is exchanged through a router.
7. The first address on any given network or subnet is reserved for _____.

   The first address on any given IPv4 network or subnet is reserved for the network itself.
8. The last address on any given IPv4 network or subnet is reserved for _____.

   The last address on any given IPv4 network or subnet is reserved for broadcast.
9. The separation of the network prefix/subnet number from the host identifier is performed by _____.

   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.
10. The number of subnetworks created by subnetting can be calculated as _____.

    The number of subnetworks created by subnetting can be calculated as 2ⁿ, where n is the number of bits used for subnetting.
11. The number of available hosts on each subnet can be calculated as _____.

    The number of available hosts on each subnet can be calculated as 2^n-2, where n is the number of bits available for the host identifier.
12. The goal of Classless Inter-Domain Routing was to _____.

    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.
13. Classless Inter-Domain Routing is based on _____.

    Classless Inter-Domain Routing is based on variable-length subnet masking (VLSM).
14. The benefits of supernetting are _____.

    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.

Assessments

• Lesson Flashcards
• Terms Flashcards
• Quiz

References

Type classification: this is a lesson resource.

Completion status: this resource is considered to be complete.

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