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 © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 11

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 © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 13

Re-using the Same Private Network 10.0.0.0, with NAT © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 14

Private IP Addresses Table 8-1 RFC 1918 Private Address Space Private IP Networks Class of Networks Number of Networks 10.0.0.0 A 1 172.16.0.0 through 172.31.0.0 B 16 192.168.0.0 through 192.168.255.0 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 © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 17

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 © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 19

Borrowing Enough Subnet and Host Bits © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 20

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 © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 23

First 10 Subnets from 172.16.0.0, 255.255.255.0 Subnet Number IP Addresses Broadcast Address 172.16.0.0 172.16.0.1 – 172.16.0.254 172.16.0.255 172.16.1.0 172.16.1.1 – 172.16.1.254 172.16.1.255 172.16.2.0 172.16.2.1 – 172.16.2.254 172.16.2.255 172.16.3.0 172.16.3.1 – 172.16.3.254 172.16.3.255 172.16.4.0 172.16.4.1 – 172.16.4.254 172.16.4.255 172.16.5.0 172.16.5.1 – 172.16.5.254 172.16.5.255 172.16.6.0 172.16.6.1 – 172.16.6.254 172.16.6.255 172.16.7.0 172.16.7.1 – 172.16.7.254 172.16.7.255 172.16.8.0 172.16.8.1 – 172.16.8.254 172.16.8.255 172.16.9.0 172.16.9.1 – 172.16.9.254 172.16.9.255 Skipping many… 172.16.254.0 172.16.254.1 – 172.16.254.254 172.16.254.255 172.16.255.0 172.16.255.1 – 172.16.255.254 172.16.255.255 © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 24

Chapter 9 Subnet Mask Conversion © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 25

Example Conversions – Binary to Prefix Binary Mask Logic Prefix Mask 11111111 11111111 11000000 00000000 Count 8 + 8 + 2 = 18 binary 1s /18 11111111 11111111 11111111 11110000 Count 8 + 8 + 8 + 4 = 28 binary 1s /28 11111111 11111000 00000000 00000000 Count 8 + 5 = 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 11111111 11111111 11000000 00000000 /28 Write 28 1s, then 4 0s, total 32 11111111 11111111 11111111 11110000 /13 Write 13 1s, then 19 0s, total 32 11111111 11111000 00000000 00000000 © 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 00000000 10000000 128 1 11000000 192 2 11100000 224 3 11110000 240 4 11111000 248 5 11111100 252 6 11111110 254 7 11111111 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 11111111 11111111 11000000 00000000 11111111 maps to 255 11000000 maps to 192 00000000 maps to 0 255.255.192.0 11111111 11111111 11111111 11110000 11110000 maps to 240 255.255.255.240 11111111 11111000 00000000 00000000 11111000 maps to 248 255.248.0.0 © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 29

Example Conversions – Decimal to Binary Decimal Mask Logic Binary Mask 255.255.192.0 255 maps to 11111111 192 maps to 11000000 0 maps to 00000000 11111111 11111111 11000000 00000000 255.255.255.2 40 240 maps to 11110000 11111111 11111111 11111111 11110000 255.248.0.0 248 maps to 11111000 11111111 11111000 00000000 00000000 © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 30

Conversion from Prefix to Decimal: Full Binary Vs. Shorthand © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 31

Conversion from Decimal to Prefix: Full Binary Vs. Shorthand © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 32

Practice Problems: Find the Mask Values in the Other Two Formats Prefix Binary Mask Decimal 11111111 11111111 11000000 00000000 255.255.255.252 /25 /16 255.0.0.0 11111111 11111111 11111100 00000000 255.254.0.0 /27 © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 33

Break 10 Min. © 2011 ITT Educational Services Inc. NT-2640 Advanced Networking: : Unit 1: Slide 34

Chapter 10 Analyzing Existing Subnet Masks © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 35

Prefix (Subnet) and Host Parts Defined by Mask’s 1s and 0s © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 36

Mask 255.255.255.0: P=24, H=8 © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 37

Class Concepts Applied to Create Three Parts © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 38

Subnet 10.1.1.0, Mask 255.255.255.0: N=8, S=16, H=8 © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 39

Relationship Between /P, N, S, and H © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 40

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 © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 42

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 10.1.1.1 255.255.255.0 Albuquerque (config-if)#interface S0/0/1 Albuquerque (config-if)#ip address 10.1.2.1 255.255.255.0 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 128000 ! 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

Loading the Cisco IOS © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 3: Slide 48

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