Transcript IP Networking UNIT 2.. - Rhema Impact Ministries

Unit 2
TCP/IP Network, Transport &
Application Layers
Chapters 5-7
NT2640.U2.PS1
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Objectives
• In this unit, students will demonstrate an:
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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
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Network Layer Addressing and
Layer 4 Protocols
Chapter 1
Chapters 5 & 6
NT2640-U2-PS1
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3
Routing Logic: PC1 Sending to PC2
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IPv4 Header
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Example 19.1
Change the following IPv4 addresses from binary notation
to dotted-decimal notation.
Solution
We replace each group of 8 bits with its equivalent decimal
number (see Appendix B) and add dots for separation.
19.6
Figure 19.2 Finding the classes in binary and dotted-decimal notation
19.7
Table 19.1 Number of blocks and block size in classful IPv4 addressing
19.8
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)
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Figure 19.7 Configuration and addresses in a subnetted network
19.10
Using Subnets
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Figure 19.8 Three-level hierarchy in an IPv4 address
19.12
Address Formats When Subnetting Is Used (Classful)
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• 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,
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Table 19.2 Default masks for classful addressing
19.15
22-1 DELIVERY
The network layer supervises the handling of the
packets by the underlying physical networks. We define
this handling as the delivery of a packet.
19.16
Direct and indirect delivery
19.17
ROUTING or FORWARDING
Forwarding means to place the packet in its route to its
destination. Forwarding requires a host or a router to
have a routing table. When a host has a packet to send
or when a router has received a packet to be forwarded,
it looks at this table to find the route to the final
destination.
Forwarding Techniques
Forwarding Process
Routing Table
19.18
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:
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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).
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Host Routing Alternatives
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Figure 22.2 Route method versus next-hop method
19.21
Figure 22.3 Host-specific versus network-specific method
19.22
Simple Routing Example, with IP Subnets
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Figure 22.5 Simplified forwarding module in classless address
19.24
Network Layer Utilities
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(ARP) Address Resolution Protocol
(DNS) Domain Name System
(DHCP) Dynamic Host Configuration Protocol
(ICMP) Internet Control Message Protocol
used for troubleshooting - Ping & Tracert
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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 )
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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.
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Address Assignment and DHCP
• DHCP Messages to Acquire an IP Address
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ICMP Echo and the ping Command
• Sample Network, ping Command
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Chapter 6
Fundamentals of TCP/IP Transport,
Applications, and Security
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TCP/IP Layer 4 Protocols: TCP and UDP
Function
Multiplexing using ports
Description
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.
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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.
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6-1 MULTIPLEXING
Whenever the bandwidth of a medium linking two devices
is greater than the bandwidth needs of the devices, the link
can be shared. Multiplexing is the set of techniques that
allows the simultaneous transmission of multiple signals
across a single data link. As data and telecommunications
use increases, so does traffic.
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Figure 6.3 Frequency-division multiplexing
2.34
Hannah Sending Packets to Jessie, with Three
Applications Using Port Numbers to Multiplex
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Popular Applications and Their Well-Known Port Numbers
Port Number
20
21
22
23
Protocol
TCP
TCP
TCP
TCP
Application
FTP data
FTP control
SSH
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
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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
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Network Security
• In the past, security threats came from geniuses or nerdy
students with lots of time.
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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.
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Every company and almost every person connects to the Internet,
making essentially the whole world vulnerable to attack.
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• Firewalls
• IDS and IPS
• VPN
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Break
10 Min.
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Chapter 7
Operating Cisco Routers
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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.
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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.
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Generic Enterprise Network Diagram
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Detailed Cabling Diagram for the Same
Enterprise Network
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Model 1841 Cisco Integrated Services
Router (ISR)
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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.
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Devices in a SOHO Network with High-Speed CATV
Internet
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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.
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SOHO Network, Using Cable Internet with an
Integrated Device
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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.
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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.
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CLI Access
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Console Connection to a Router
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Terminal Settings for Console Access
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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.
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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.
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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
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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.
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User and Privileged Modes
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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.
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Key Sequences for Command Edit and Recall
Keyboard Command
Up arrow or Ctrl-p
Ctrl-d
What Happens
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.)
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.)
This moves the cursor backward in the currently displayed
command without deleting characters. (The b stands for back.)
This moves the cursor forward in the currently displayed
command without deleting characters. (The f stands for
forward.)
This moves the cursor backward in the currently displayed
command, deleting characters.
This moves the cursor directly to the first character of the
currently displayed command.
This moves the cursor directly to the end of the currently
displayed command.
This redisplays the command line with all characters. It’s
useful when messages clutter the screen.
This deletes a single character.
Esc-b
This moves back one word.
Esc-f
This moves forward one word.
Down arrow or Ctrl-n
Left arrow or Ctrl-b
Right arrow or Ctrl-f
Backspace
Ctrl-a
Ctrl-e
Ctrl-r
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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.
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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.
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CLI Configuration Mode Versus Exec Modes
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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.
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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)
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Navigating Between Different
Configuration Modes
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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)#
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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)#
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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.
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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.
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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
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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.
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Copying and Erasing Configuration Files
• Locations for Copying and Results from Copy Operations
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IFS Filenames for the Startup and
Running Config Files
Config File Common Name
Alternative Names
startup-config
nvram:
nvram:startup-config
running-config
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system:running-config
Entering the Setup Mode
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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 startupconfig an running-config
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Summary
• In this unit, we discussed:
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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
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Break
10 Min.
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Assignment 1
• Complete Review Questions on Chapters 1 to 6
• Read Chapter 4 to 7
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