© 2011 itt educational services inc. nt-2640 advanced networking: unit 2: slide 1 unit 2 tcp/ip...

© 2011 ITT Educational Services Inc. NT-2640 Advanced Networking: Unit 2: Slide 1

Unit 2

TCP/IP Network, Transport & Application Layers

Chapters 5-7

NT2640.U2.PS1

© 2011 ITT Educational Services Inc. NT-2640 Advanced Networking: : Unit 2: Slide 2

Objectives

• In this unit, students will demonstrate an: Understanding of Network Layer Addressing Understand of Basic IP Routing Concepts Understanding of Basic IP Subnetting Principles Understanding of the Differences between and the Features of the

Layer 4 Protocols TCP & UDP Understanding of Basic Network Security Concepts including Common

Issues and Defenses Understanding Tasks Involved in the Installation of Cisco IOS Devices Understanding the Basic Tasks Involved in the Accessing the Cisco

IOS CLI Environment and Utilizing the Help Subsystem


Network Layer Addressing and Layer 4 Protocols

Chapters 5 & 6

NT2640-U2-PS1

Chapter 1

3

Routing Logic: PC1 Sending to PC2

© 2011 ITT Educational Services Inc. NT-2640 Advanced Networking: Unit 2: Slide 4

IPv4 Header

© 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 2: Slide 5

19.6

Change the following IPv4 addresses from binary notation to dotted-decimal notation.

Example 19.1

SolutionWe replace each group of 8 bits with its equivalent decimal number (see Appendix B) and add dots for separation.

19.7

Figure 19.2 Finding the classes in binary and dotted-decimal notation

19.8

Table 19.1 Number of blocks and block size in classful IPv4 addressing

Class First Octet Range

Valid Network Numbers*

Total Number for This Class of Network

Number of Hosts Per Network

A 1 to 126 1.0.0.0 to 126.0.0.0 27 – 2 (126) 224 – 2 (16,777,214)

B 128 to 191 128.0.0.0 to 191.255.0.0 214 (16,384) 216 – 2 (65,534)

C 192 to 223 192.0.0.0 to 223.255.255.0

221 (2,097,152) 28 – 2 (254)


19.10

Figure 19.7 Configuration and addresses in a subnetted network

Using Subnets


19.12

Figure 19.8 Three-level hierarchy in an IPv4 address

Address Formats When Subnetting Is Used (Classful)


• Address Formats When Subnetting Is Used (Classless)

• IP addressing with subnetting uses a concept called a subnet mask. A subnet mask helps define the structure of an IP address,


19.15

Table 19.2 Default masks for classful addressing

19.16

22-1 DELIVERY22-1 DELIVERY

The network layer supervises the handling of the The network layer supervises the handling of the packets by the underlying physical networks. We define packets by the underlying physical networks. We define this handling as the delivery of a packet.this handling as the delivery of a packet.

19.17

Direct and indirect delivery

19.18

ROUTING or FORWARDINGROUTING or FORWARDING

Forwarding means to place the packet in its route to its Forwarding means to place the packet in its route to its destination. Forwarding requires a host or a router to destination. Forwarding requires a host or a router to have a routing table. When a host has a packet to send have a routing table. When a host has a packet to send or when a router has received a packet to be forwarded, or when a router has received a packet to be forwarded, it looks at this table to find the route to the final it looks at this table to find the route to the final destination. destination.

Forwarding TechniquesForwarding ProcessRouting Table

IP Routing or Forwarding

• Hosts actually use some simple routing logic when choosing where to send a packet. This two-step logic is as follows: Step 1 If the destination IP address is in the

same subnet as I am, send the packet directly to that destination host.

Step 2 If the destination IP address is not in the same subnet as I am, send the packet to my default gateway (a router’s Ethernet interface on the subnet).


Host Routing Alternatives


19.21

Figure 22.2 Route method versus next-hop method

19.22

Figure 22.3 Host-specific versus network-specific method

Simple Routing Example, with IP Subnets


19.24

Figure 22.5 Simplified forwarding module in classless address

Network Layer Utilities

• (ARP) Address Resolution Protocol• (DNS) Domain Name System• (DHCP) Dynamic Host Configuration Protocol• (ICMP) Internet Control Message Protocol

used for troubleshooting - Ping & Tracert


DNS Request and Reply

• Hannah simply sends a DNS request to the server, supplying the name Jessie, or jessie.example.com, and the DNS replies with the IP address (10.1.1.2 )


ARP Process

• As soon as a host knows the IP address of the other host, the sending host may need to know the MAC address used by the other computer.


Address Assignment and DHCP

• DHCP Messages to Acquire an IP Address


ICMP Echo and the ping Command

• Sample Network, ping Command


Chapter 6

Fundamentals of TCP/IP Transport, Applications, and Security


TCP/IP Layer 4 Protocols: TCP and UDPFunction DescriptionMultiplexing using ports Function that allows receiving hosts to choose the

correct application for which the data is destined, based on the port number.

Error recovery (reliability) Process of numbering and acknowledging data with Sequence and Acknowledgment header fields.

Flow control using windowing Process that uses window sizes to protect buffer space and routing devices.

Connection establishment and termination Process used to initialize port numbers and Sequence and Acknowledgment fields.

Ordered data transfer and data segmentation Continuous stream of bytes from an upper-layer process that is “segmented” for transmission and delivered to upper-layer processes at the receiving device, with the bytes in the same order.


Multiplexing Using TCP Port Numbers

• TCP provides a lot of features to applications, at the expense of requiring slightly more processing and overhead, as compared to UDP.

• TCP and UDP both use a concept called multiplexing. • Multiplexing by TCP and UDP involves the process of how a

computer thinks when receiving data. • The computer might be running many applications, such as a

web browser, an e-mail package, or an Internet VoIP application (for example, Skype).

• TCP and UDP multiplexing enables the receiving computer to know which application to give the data to.


2.33

6-1 MULTIPLEXING6-1 MULTIPLEXING

Whenever the bandwidth of a medium linking two devices Whenever the bandwidth of a medium linking two devices is greater than the bandwidth needs of the devices, the link is greater than the bandwidth needs of the devices, the link can be shared. Multiplexing is the set of techniques that can be shared. Multiplexing is the set of techniques that allows the simultaneous transmission of multiple signals allows the simultaneous transmission of multiple signals across a single data link. As data and telecommunications across a single data link. As data and telecommunications

use increases, so does trafficuse increases, so does traffic..

2.34

Figure 6.3 Frequency-division multiplexing

Hannah Sending Packets to Jessie, with Three Applications Using Port Numbers to Multiplex


Popular Applications and Their Well-Known Port Numbers

Port Number Protocol Application20 TCP FTP data21 TCP FTP control22 TCP SSH23 TCP Telnet

25 TCP SMTP

53 UDP, TCP DNS

67, 68 UDP DHCP

69 UDP TFTP

80 TCP HTTP (WWW)

110 TCP POP3

161 UDP SNMP

443 TCP SSL

16, 384–32, 767 UDP RTP-based Voice (VoIP) and Video


Connection & Connectionless Protocols

• Connection-oriented protocol: A protocol that requires an exchange of messages before data transfer begins or that has a required preestablished correlation between two endpoints

• Connectionless protocol: A protocol that does not require an exchange of messages and that does not require a preestablished correlation between two endpoints


Network Security

• In the past, security threats came from geniuses or nerdy students with lots of time. The numbers of these people were relatively small. Their main motivation was to prove that they could break into another

network. The number of potential attackers and the sophistication of the attacks

have increased exponentially.

• Attacks that once required attackers to have an advanced degree in computing now can be done with easily downloaded and freely available tools that the average junior-high student can figure out how to use. Every company and almost every person connects to the Internet,

making essentially the whole world vulnerable to attack.


• Firewalls• IDS and IPS• VPN



Break

10 Min.

Chapter 7

Operating Cisco Routers


Cisco Routers


• Cisco routers need to know several pieces of information before they can start routing IP packets.

• First, they need to know which of their physical interfaces currently connect to real LANs and WANs.

• Next, the router needs to know its IP address and mask for each of these interfaces.

• The router can then use each interface’s IP address/mask pair to calculate the subnet ID of the subnet connected to that interface.

• Finally, the routers need to advertise information about the subnets, so that all routers learn about all subnets, and can then choose the best route with which to forward packets to reach each subnet.

Installing Cisco Routers

• Routers collectively provide the main feature of the network layer—the capability to forward packets end-to-end through a network.

• Routers forward packets by connecting to various physical network links, like Ethernet, serial links, and Frame Relay, and then using Layer 3 routing logic to choose where to forward each packet.

• A typical enterprise network has a few centralized sites as well as lots of smaller remote sites.

• To support devices at each site (the computers, IP phones, printers, and other devices), the network includes at least one LAN switch at each site.


Generic Enterprise Network Diagram


Detailed Cabling Diagram for the Same Enterprise Network


Model 1841 Cisco Integrated Services Router (ISR)


Router Installation

• Step 1: Connect any LAN cables to the LAN ports.

• Step 2: If using an external CSU/DSU, connect the router’s serial interface to the CSU/DSU, and the CSU/DSU to the line from the telco.

• Step 3: If using an internal CSU/DSU, connect the router’s serial interface to the line from the telco.

• Step 4: Connect the router’s console port to a PC (using a rollover cable), as needed, to configure the router.

• Step 5: Connect a power cable from a power outlet to the power port on the router.

• Step 6: Turn on the router.


Devices in a SOHO Network with High-Speed CATV Internet


Steps for Install a SOHO router

• Step 1: Connect a UTP straight-through cable from the router to the switch.

• Step 2: Connect a UTP straight-through cable from the router to the cable modem.

• Step 3: Connect the router’s console port to a PC (using a rollover cable), as needed, to configure the router.

• Step 4: Connect a power cable from a power outlet to the power port on the router.

• Step 5: Turn on the router.


SOHO Network, Using Cable Internet with an Integrated Device


Accessing the CLI• Cisco IOS Software, the operating system (OS) that runs on Cisco

enterprise-class routers, implements and controls logic and functions performed by a Cisco router.

• Besides controlling the router’s performance and behavior, Cisco IOS also defines an interface for humans called the CLI.

The Cisco IOS CLI allows the user to use a terminal emulation program, which accepts text entered by the user.

When the user presses Enter, the terminal emulator sends that text to the router. The router processes the text as if it is a command, does what the command says, and

sends text back to the terminal emulator. The router CLI can be accessed through three popular methods—the console, Telnet, and

Secure Shell (SSH). Two of these methods (Telnet and SSH) use the IP network in which the router resides to

reach the router.

• The console is a physical port built specifically to allow access to the CLI.


CLI Access


Console Connection to a Router


Terminal Settings for Console Access


Accessing the CLI with Telnet and SSH

• To use Telnet, the user must install a Telnet client software package on his or her PC.

• Most terminal emulator software packages today include both Telnet and SSH client functions.

• The router runs Telnet server software by default, but the router does need to have an IP address configured so that it can send and receive IP packets.

• Additionally, the network between the PC and router needs to be up and working so that the PC and router can exchange IP packets.


Password Security for CLI Access

• By default, a Cisco router is very secure as long as the router is locked inside a room.

• By default, a router allows only console access, but no Telnet or SSH access.

• From the console, you can gain full access to all router commands, and if so inclined, you can stop all functions of the router.

• However, console access requires physical access to the router, so allowing console access for routers just removed from the shipping boxes is reasonable.


CLI Password Configuration: Console and Telnet

Access From Password Type Sample Configuration

Console Console password line console 0 login password faith

Telnet vty password line vty 0 15 login password love


User and Enable (Privileged) Modes

• All three CLI access methods covered so far (console, Telnet, and SSH) place the user in an area of the CLI called user EXEC mode.

• User EXEC mode, sometimes also called user mode, allows the user to look around but not break anything.

• The “EXEC mode” part of the name refers to the fact that in this mode, when you enter a command, the router executes the command and then displays messages that describe the command’s results.

• Cisco IOS supports a more powerful EXEC mode called enable mode (also known as privileged mode or privileged EXEC mode).

• Enable mode is so named because the enable command is used to reach this mode.

• Privileged mode earns its name because powerful, or privileged, commands can be executed there. You can use the reload command, which tells the router to reinitialize or reboot Cisco IOS, only from enable mode.


User and Privileged Modes


CLI Help Features

What You Enter What Help You Get

? Help for all commands available in this mode.

help Text describing how to get help. No actual command help is given.

command ? Text help describing all the first parameter options for the command.

com? A list of commands that start with com.

command parm? This style of help lists all parameters beginning with parm. (Notice that there is no space between parm and the ?.)

command parm<Tab> If you press the Tab key midword, the CLI either spells the rest of this parameter at the command line or does nothing. If the CLI does nothing, it means that this string of characters represents more than one possible next parameter, so the CLI does not know which one to spell out.

command parm1 ? If a space is inserted before the question mark, the CLI lists all the next parameters and gives a brief explanation of each.


Key Sequences for Command Edit and RecallKeyboard Command What HappensUp arrow or Ctrl-p This displays the most recently used command. If you press it

again, the next most recent command appears, until the history buffer is exhausted. (The p stands for previous.)

Down arrow or Ctrl-n If you have gone too far back into the history buffer, these keys take you forward to the more recently entered commands. (The n stands for next.)

Left arrow or Ctrl-b This moves the cursor backward in the currently displayed command without deleting characters. (The b stands for back.)

Right arrow or Ctrl-f This moves the cursor forward in the currently displayed command without deleting characters. (The f stands for forward.)

Backspace This moves the cursor backward in the currently displayed command, deleting characters.

Ctrl-a This moves the cursor directly to the first character of the currently displayed command.

Ctrl-e This moves the cursor directly to the end of the currently displayed command.

Ctrl-r This redisplays the command line with all characters. It’s useful when messages clutter the screen.

Ctrl-d This deletes a single character.

Esc-b This moves back one word.

Esc-f This moves forward one word.


Debug and Show Commands• The single most popular Cisco IOS command is the show command. • The show command has a large variety of options, and with those options,

you can find the status of almost every feature of Cisco IOS. • Essentially, the show command lists the currently known facts about the

router’s operational status. • The only work the router does in reaction to show commands is to find the

current status and list the information in messages sent to the user.• A less popular command is the debug command. • Like the show command, debug has many options. • Instead of just listing messages about the current status, the debug

command asks the router to continue monitoring different processes in the router.

• The router then sends ongoing messages to the user when different events occur.


Configuring Cisco IOS Software• Configuration mode is another mode for the Cisco CLI, similar

to user mode and privileged mode. • User mode lets you issue non-disruptive commands and

displays some information. • Privileged mode supports a superset of commands compared

to user mode, including commands that might harm the router. • However, none of the commands in user or privileged mode

changes the router’s configuration. • Configuration mode accepts configuration commands—

commands that tell the router the details of what to do, and how to do it.


CLI Configuration Mode Versus Exec Modes


Configuration Submodes and Contexts

• Configuration mode itself contains a multitude of subcommand modes.

• Context-setting commands move you from one configuration subcommand mode, or context, to another.

• These context-setting commands tell the router the topic about which you will enter the next few configuration commands.

• More importantly, the context tells the router the topic you care about right now, so when you use the ? to get help, the router gives you help about that topic only.


Router Mode Movements• Movement from enable mode to global configuration mode by using the

configure terminal EXEC command• Using a hostname Fred global configuration command to configure the

router’s name• Movement from global configuration mode to console line configuration

mode (using the line console 0 command)• Setting the console’s simple password to hope (using the password hope

line subcommand)• Movement from console configuration mode to interface configuration mode

(using the interface command)• Setting the speed to 100 Mbps for interface Fa0/1 (using the speed 100

interface subcommand)• Movement interface configuration mode back to global configuration mode

(using the exit command)


Navigating Between Different Configuration Modes

• Router#configure terminal• Router(config)#hostname Fred• Fred(config)#line console 0• Fred(config-line)#password hope• Fred(config-line)#interface FastEthernet 0/1• Fred(config-if)#speed 100• Fred(config-if)#exit• Fred(config)#


Common Router Configuration Modes

Prompt Name of Mode

Context-setting Command(s) to Reach This Mode

hostname(config)# Global None—first mode after configure terminal

hostname(config-line)# Line line console 0

line vty 0 15

hostname(config-if)# Interface interface type number


Storing Router Configuration Files• RAM: Sometimes called DRAM for Dynamic Random-Access Memory, RAM is used

by the router just as it is used by any other computer: for working storage. The running (active) configuration file is stored here.

• ROM: Read-Only Memory (ROM) stores a bootstrap (or boothelper) program that is loaded when the router first powers on. This bootstrap program then finds the full Cisco IOS image and manages the process of loading Cisco IOS into RAM, at which point Cisco IOS takes over operation of the router.

• Flash memory: Either a chip inside the router or a removable memory card, Flash memory stores fully functional Cisco IOS images and is the default location where the router gets its Cisco IOS at boot time. Flash memory also can be used to store any other files, including backup copies of configuration files.

• NVRAM: Nonvolatile RAM (NVRAM) stores the initial or startup configuration file that is used when the router is first powered on and when the router is reloaded.


Cisco Router Memory Types

• Cisco IOS stores the collection of configuration commands in a configuration file. In fact, routers use multiple configuration files—one file for the initial configuration used when powering on, and another configuration file for the active, currently used running configuration as stored in RAM.


Names and Purposes of the Two Main Cisco IOS Configuration Files

Configuration Filename

Purpose Where It Is Stored

Startup-config Stores the initial configuration used any time the router reloads Cisco IOS.

NVRAM

Running-config Stores the currently used configuration commands. This file changes dynamically when someone enters commands in configuration mode.

RAM


Configuration Mode, changes for the running-config file

• Step 1: The original hostname command on the router, with the startup-config file matching the running-config file.

• Step 2: The hostname command changes the hostname, but only in the running-config file.

• Step 3: The show running-config and show startup-config commands are shown, with only the hostname commands displayed for brevity, to make the point that the two configuration files are now different.


Copying and Erasing Configuration Files

• Locations for Copying and Results from Copy Operations


IFS Filenames for the Startup and Running Config Files

Config File Common Name Alternative Names

startup-config nvram:

nvram:startup-config

running-config system:running-config


Entering the Setup Mode



Check Point

1. What type of cable is used for console access to a Cisco router and what is the serial communication connection properties?

2. Describe the differences between NVRAM and flash storage

3. Describe the differences between enable mode and configuration mode

4. Describe the differences between startup-config an running-config


Summary

• In this unit, we discussed: Network Layer Addressing Basic IP Routing Concepts Basic IP Subnetting Principles Differences between and Features of the Layer 4

Protocols TCP & UDP Basic Network Security Concepts including Common

Issues and Defenses Tasks Involved in Installing Cisco IOS Devices Basic Tasks Involved in Accessing the Cisco IOS CLI

Environment and Using the Help Subsystem


Break

10 Min.

Assignment 1

• Complete Review Questions on Chapters 1 to 6

• Read Chapter 4 to 7


© 2011 itt educational services inc. nt-2640 advanced networking: unit 2: slide 1 unit 2 tcp/ip...

Documents

itt educational services

wan technologies

deliverythe network

advanced networking

tcpip network

classful ipv4

simple routing logic

basic tasks