© 2011 ITT Educational Services Inc.

Unit 3 IP Subnetting and Basic Router Configuration Chapters 8-11 NT2640.U3.PS1
© 2011 ITT Educational Services Inc. NT-2640 Advanced Networking: Unit 3: Slide 1

In this unit, students will demonstrate an:
Objectives In this unit, students will demonstrate an: Ability to Identify and Analyze IP Subnet Needs Understanding of the Conversion Process from Binary to Dotted Decimal Understanding of the Conversion Process from Binary to Prefix Notation Understanding of the Calculation Process for IP Subnets with Classful and Classless Masks Understanding of the Basic Configuration Process for Cisco IOS Devices Understanding of the Cisco IOS Router Specific Items © 2011 ITT Educational Services Inc. NT-2640 Advanced Networking: : Unit 3: Slide 2

Perspectives on IPv4 Subnetting and Subnet Mask Conversion Chapters 8 & 9 NT2640-U2-PS1
© 2011 ITT Educational Services Inc. NT-2640 Advanced Networking: : Unit 3: Slide 3 3

IP Subnetting Subnet Planning, Design, and Implementation Tasks
Today, a network engineer practically never has the opportunity to design a new internetwork from nothing. Instead, an engineer might make design changes to an existing internetwork, and then implement those changes. © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 4

Analyze Needs The four basic questions that can be used to analyze the addressing and subnetting needs for any new or changing Enterprise network are: 1. Which hosts should be grouped together into a subnet? 2. How many subnets does this network require? 3. How many host IP addresses does each subnet require? 4. Will we use a single subnet size for simplicity, or not? © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 5

PC A and B in One Subnet, PC C in a Different Subnet
Subnets PC A and B in One Subnet, PC C in a Different Subnet © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 6

Determining the Number of Subnets
To determine the number of subnets required, the engineer must think about the internetwork as documented and apply the following rules. To do so, the engineer requires access to network diagrams, VLAN configuration details, and if you use Frame Relay WANs, details about the Permanent Virtual Circuits (PVCs). © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 7

Large Branch B1 with 50 Hosts/Subnet
© 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 8

Subnet Size Concepts © 2011 ITT Educational Services Inc.
NT-2640 Wan Technologies: Unit 3: Slide 9

One Size Subnet Fits All
To choose to use a single size subnet in a network, you must use the same mask for all subnets, because the mask defines the size of the subnet. But which mask? One requirement to consider when choosing that one mask is the following: that one mask must provide enough host IP addresses to support the largest subnet. To do so, the number of host bits (H) defined by the mask must be large enough so that 2H – 2 is larger than (or equal to) the number of host IP addresses required in the largest subnet. © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 10

Chapters 10 and 11 Analyzing Existing Subnet Mask and Operating Cisco Routers

Public IP Networks Public IP networks, and the administrative processes surrounding them, ensure that all the companies that connect to the Internet all use unique IP addresses. In particular, once a public IP network has been assigned to a company, only that company should use the addresses in that network. That guarantee of uniqueness means that Internet routing can work well, because there are no duplicate public IP addresses. © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 12

Two Companies with Unique Public IP Networks

Re-using the Same Private Network 10.0.0.0, with NAT

Private IP Addresses Table 8-1 RFC 1918 Private Address Space
Private IP Networks Class of Networks Number of Networks A 1 through B 16 through C 256 © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 15

Choose the Mask The number of subnets required
The number of hosts/subnet required That a choice was made to use only 1 mask for all subnets, so that all subnets are the same size (same number of hosts/subnet) The classful IP network number that will be subnetted © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 16

Unsubnetted Class A, B, and C Networks

Size of Unsubnetted Class A, B, or C Networks
Class B: 216 – 2 = 65,534 Class C: 28 – 2 = 254 © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 18

The Concept of Borrowing Host Bits

Borrowing Enough Subnet and Host Bits

Powers of 2 Reference for Designing Masks
Number of Bits 2X 2X – 2 1 2 4 3 8 6 16 14 5 32 30 64 62 7 128 126 256 254 9 512 510 10 1024 1022 11 2048 2046 12 4096 4094 © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 21

Masks and Mask Formats The subnet mask is a 32-bit binary number with a number of binary 1s on the left, and with binary 0s on the right. By definition, the number of binary 0s equals the number of host bits – in fact, that is exactly how the mask communicates the idea of the size of the host part of the addresses in a subnet. The beginning bits in the mask equal binary 1, with those bit positions representing the combined network and subnet parts of the addresses in the subnet. © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 22

Creating the Subnet Mask – Binary – Class B Network

First 10 Subnets from 172.16.0.0, 255.255.255.0 Subnet Number
IP Addresses Broadcast Address – – – – – – – – – – Skipping many… – – © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 24

Chapter 9 Subnet Mask Conversion

Example Conversions – Binary to Prefix
Binary Mask Logic Prefix Mask Count = 18 binary 1s /18 Count = 28 binary 1s /28 Count = 13 binary 1s /13 © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 26

Example Conversions – Prefix to Binary
Prefix Mask Logic Binary Mask /18 Write 18 1s, then 14 0s, total 32 /28 Write 28 1s, then 4 0s, total 32 /13 Write 13 1s, then 19 0s, total 32 © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 27

The Nine Possible Values in One Octet of a Subnet Mask
Binary Mask Octet Decimal Equivalent Number of Binary 1s 128 1 192 2 224 3 240 4 248 5 252 6 254 7 255 8 © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 28

Example Conversions – Binary to Decimal
Binary Mask Logic Decimal Mask maps to 255 maps to 192 maps to 0 maps to 240 maps to 248 © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 29

Example Conversions – Decimal to Binary
Decimal Mask Logic Binary Mask 255 maps to 192 maps to 0 maps to 240 maps to 248 maps to © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 30

Conversion from Prefix to Decimal: Full Binary Vs. Shorthand

Conversion from Decimal to Prefix: Full Binary Vs. Shorthand

Practice Problems: Find the Mask Values in the Other Two Formats
Prefix Binary Mask Decimal /25 /16 /27 © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 33

Chapter 10 Analyzing Existing Subnet Masks

Prefix (Subnet) and Host Parts Defined by Mask’s 1s and 0s

Class Concepts Applied to Create Three Parts

Relationship Between /P, N, S, and H

Calculating the number of hosts/subnet
Step 1. Convert the mask to prefix format (/P) as needed Step 2. Determine N based on the class Step 3. Calculate S = P – N Step 4. Calculate H = 32 – P Step 5. Calculate hosts/subnet: 2H – 2 Step 6. Calculate number of subnet: 2S © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 41

Chapter 11 Cisco Router Configuration

Both need some passwords to secure access to the CLI.
As you might imagine, both routers and switches need some of the same configuration settings. Both need a name. Both need some passwords to secure access to the CLI. To reach a router’s enable mode, a user must reach user mode either from the console or from a Telnet or SSH session, and then use the enable command. © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 43

Configuring Basic Passwords & Hostname
Router#configure terminal Router(config)#enable secret cisco Router(config)#hostname Emma Emma(config)#line console 0 Emma(config-line)#password faith Emma(config-line)#login Emma(config-line)#exit Emma(config)#line vty 0 15 Emma(config-line)#password love Emma(config)#exit Emma# © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 44

Configuring IP Addresses on Cisco Routers
Albuquerque#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Albuquerque (config)#interface Fa0/0 Albuquerque (config-if)#ip address Albuquerque (config-if)#interface S0/0/1 Albuquerque (config-if)#ip address Albuquerque (config-if)#^Z © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 45

Router Configuration with clock rate Command
Albuquerque#show running-config ! lines omitted for brevity interface Serial0/0/1 clock rate ! interface Serial0/1/0 bandwidth 128 © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 46

Powering on a Router When a router first powers on, it follows these four steps: 1. The router performs a power-on self-test (POST) to discover the hardware components and verify that all components work properly. 2. The router copies a bootstrap program from ROM into RAM, and runs the bootstrap program. 3. The bootstrap program decides which IOS image (or other OS) to load into RAM, and loads that OS. After loading the IOS image, the bootstrap program hands over control of the router hardware to the newly loaded OS. 4. If the bootstrap program loaded IOS, IOS finds the configuration file (typically the startup-config file in NVRAM) and loads it into RAM as the running-config. © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 47

Summary In this unit, we discussed:
Identifying and Analyzing IP Subnet Needs Converting from Binary to Dotted Decimal Converting from Binary to Prefix Notation The Calculation Process for IP Subnets with Classful and Classless Masks The Basic Configuration Process for Cisco IOS Devices Cisco IOS Router-Specific Items © 2011 ITT Educational Services Inc. NT-2640 Advanced Networking: : Unit 3: Slide 49

Assignments Assignment 3.1: IP Subnetting
Discussion 3.1IP Subnetting – Exercise Subnetting Lab 3 © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 50

Lab 3.1 Setting Router passwords Configuring Router IP settings
Configuring SSH Terminal History I Rebuild a Configuration SSH and Telnet Basic Router Configuration and Command Line Interface Switch and Router Security © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 51

© 2011 ITT Educational Services Inc.

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