HTML Injection Attacks: Impact and Mitigation Strategies
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Lesson 1 slideshow
1. Š 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 1
www.professordkinney.com
2. Building A Simple network
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Instructional Design-Computer Networking -
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3. Objectives
ī Describe how networking works
ī Host-to-host communication
ī Introducing LANs
ī Understanding Ethernet and Switch
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Instructional Design-Computer Networking -
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4. Network Structure
īDefine a network
īdata or information networks capable of carrying many
different types of communications
īDefine the components of a network
â Network components
âĸ hardware
âĸ software
08/02/13
Instructional Design-Computer Networking -
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5. Network Structure
īEnd Devices and their Role in the Network
â End devices form interface with human network &
communications network
â Role of end devices:
âĸ client
âĸ server
âĸ both client and server
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Instructional Design-Computer Networking -
Bridges Educational Group
6. Network Structure
īIdentify the role of an intermediary device in a data
network and be able to contrast that role with the role
of an end device
â Role of an intermediary device
âĸ provides connectivity and ensures data flows
across network
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Instructional Design-Computer Networking -
Bridges Educational Group
8. Network Structure
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īDefine Wide Area Networks (WANs)
ī- LANs separated by geographic distance are connected
by a network known as a Wide Area Network (WAN)
10. Host-to-Host Communications
īThe OSI reference model provides a means of
describing how data is transmitted over a network.
The model addresses hardware, software, and data
transmission.
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Instructional Design-Computer Networking -
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11. Host-to-Host Communications
Peer-to-Peer Communication
So that data packets can travel from the source to the
destination, each layer of the OSI model at the source must
communicate with its peer layer at the destination. This topic
describes the process of peer-to-peer communication.
īDuring the process of peer-to-peer communication, the
protocols at each layer exchange packets of information called
protocol data units (PDUs) between peer layers.
īThese data packets originate at a source on a network and then
travel to a destination. Each layer depends on the OSI layer
below it to provide a service. To perform its service function, the
lower layer uses encapsulation to put the protocol data unit
(PDU) from the upper layer into lower layer data field. Each
layer then adds whatever headers the layer needs to perform its
function. As the data moves down from Layer 7 through Layer 2
of the OSI model, additional headers are added.
08/02/13
Instructional Design-Computer Networking -
Bridges Educational Group
12. Host-to-Host Communications
īThe network layer provides a service to the transport layer,
and the transport layer presents data to the network
subsystem. The network layer moves the data through the
Internet by encapsulating the data and attaching a header
to create a packet (the Layer 3 PDU). The header contains
information required to complete the transfer, such as
source and destination logical addresses.
īThe data link layer provides a service to the network layer
by encapsulating the network layer packet in a frame (the
Layer 2 PDU). The frame header contains the physical
addresses required to complete the data link functions,
and the frame trailer contains the FCS.
īThe physical layer provides a service to the data link layer,
encoding the data-link frame into a pattern of 1s and 0s
(bits) for transmission on the medium (usually a wire) at
Layer 1.
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14. Ethernet
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īOSI model layers 1 (physical) and 2 (data link)
īTCP/IP model Network Access layer
Application
Presentation
Session
Transport
Network
Data link
Physical
Ethernet
Application
Transport
Internet
Network Access
15. Ethernet
īThe most common LAN technology
īDifferent media (copper cable, optical fibre)
īDifferent bandwidths (10, 100Mbps, Gbps, +)
īSame addressing scheme
īSame basic frame format
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16. Ethernet history
īFirst LAN was Ethernet, designed at Xerox
ī1980 Ethernet standard published by DIX (Digital, Intel, Xerox)
ī1985 IEEE modified Ethernet standard and published as 802.3
Ethernet802.3
802.2MAC
LLC
17. Advantages of Ethernet
īSimplicity and ease of maintenance
īAbility to incorporate new technologies (e.g. fibre
optic, higher bandwidths)
īReliability
īLow cost of installation and upgrade
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Instructional Design-Computer Networking -
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18. Ethernet Frame
Packet
Packet TrailerFrame header
Packet from
Network layer is
encapsulated
Preamble Destination
address
Start of
frame
delimiter
Source
address
Length
/type
7 1 6 6 2
Packet
Data
Frame
Check
Seq.
46-1500 4
Field size in bytes. Preamble and SFD are not counted in
frame size. Frame is 64-1518 (later 1522) bytes.
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Instructional Design-Computer Networking -
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19. Hub and Switch
īShared medium
īShared bandwidth
īCollisions
īPoint to point links
īDedicated bandwidth
īUse full duplex â no collisions
Hub
Switch
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20. Switching table
īSwitch builds a switching table
matching its port numbers to the
MAC addresses of devices connected
to them.
īWhen a frame arrives, it reads the
destination MAC address, looks it
up in the table, finds the right port
and forwards the frame.
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21. Flooding
īIf the switch does not find the destination address in
its table then it floods the frame through all ports
except the incoming port.
īBroadcast messages are flooded.
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22. Learning addresses
īThe switch learns addresses by looking at the source
MAC address of an incoming frame.
īIt then matches the address to the port where the
frame came in and puts the information in its table.
īEntries are time stamped and removed from the table
when the time runs out.
īThey can be refreshed when another frame comes in
from the same host.
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23. ARP table
īA host wants to send a message.
īIt knows the destination IP address and puts it in the
packet header.
īIt looks in its ARP table and finds the corresponding
MAC address.
īIt puts the MAC address in the frame header.
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Instructional Design-Computer Networking -
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24. Internetwork Operating System
īMost Cisco devices use the Cisco IOS.
īDetails vary with the device and feature set.
īNormal access through a command line.
īStored in flash memory and can be upgraded.
īUsually copied into RAM when the device is powered
on, and run from RAM.
25. Router prompts
User EXEC mode
Privileged EXEC mode
Global Configuration mode
Specific Configuration modes
Router>
Router#
Router(config)#
Router(config-if)#
and others
26. EXEC modes
īYou log in to User EXEC mode
Router>
īYou can give basic monitoring commands but cannot
change the configuration
īEnter enable to go to Privileged EXEC mode
Router#
īPassword may be used for security
īYou can give more commands and can go to
configuration modes
27. Configuration modes
īStart in privileged EXEC mode and enter the
configure terminal (config t) command
Router# config t
Router(config)#
īThe prompt changes
īThis is global configuration mode
īAdditional commands take you to interface
configuration, router configuration etc.
28. Console password
īParis(config)#line con 0
īParis(config-line)#password cisco
īParis(config-line)#login
īParis(config-line)#exit
īRestricts access via the console
īUse cisco as the password in labs.
īUse a proper strong password on production
networks
29. Vty password for Telnet
īParis(config)#line vty 0 4
īParis(config-line)#password cisco
īParis(config-line)#login
īParis(config-line)#exit
īAllows and restricts access via 5 vty lines
īUse cisco as the password in labs.
īUse a proper strong, different password on
production networks
30. Enable and enable secret
īParis(config)#enable secret class
īThe password class is needed when you type enable
to enter privileged exec mode
īThis password is encrypted
īParis(config)#enable password cisco
īNot encrypted, used on older routers
īIf you configure both, then only the enable secret is
used.
31. Back up to TFTP server
īStart TFTP server software on host
īParis#copy running-config tftp
īRemote host []? 172.16.1.1
īName of configuration file to write [Paris-config]?
Paris12Oct07
īWrite file Paris12Oct07 to 172.16.1.1? [confirm] y
īWriting Paris12Oct07 ! ! ! ! ! ! [OK]
32. Erase startup configuration
īParis#erase NVRAM:startup-config
īParis#erase startup-config
īParis#erase start
īIf you reload, then the router starts up with the
default configuration. No passwords, no IP addresses
etc.
īCaution if you get this command wrong then you
could erase something else, e.g. IOS
33. Restore file from TFTP server
īRouter#copy tftp running-config
īYou will be prompted for IP address and file name.
īConfiguration is copied into RAM and takes effect at
once.
īSave to NVRAM.
34. Configure a router interface
īParis(config)#interface FastEthernet 0/0
īParis(config-if)#ip address 172.16.1.1 255.255.0.0
īParis(config-if)#no shutdown
īParis(config-if)#exit
īInterface names vary, depending on whether the
router is modular and on the bandwidth.
īE.g. interface Ethernet 0 on an older router
35. Configure a router interface
īParis(config)#interface serial 0/0
īParis(config-if)#ip address 192.168.4.1 255.255.255.0
ī(Paris(config-if)#clock rate 64000)
īParis(config-if)#no shutdown
īParis(config-if)#exit DCE only
36. Switch IP address
īThe switch IP address goes on a virtual interface, not
a real one, normally VLAN1.
īSwA(config)#interface VLAN1
īSwA(config-if)#ip address 172.16.255.1 255.255.0.0
īSwA(config-if)#no shutdown
īSwA(config-if)#exit
37. Interface â show commands
īshow interfaces states whether up or down, gives
some protocol information and statistics about
interface use.
īshow ip interface gives IP addresses and much
more.
īshow ip interface brief gives summary of IP
addresses and whether up/down. Very useful
command.
38. Summary
īNetwork communications using peer to peer hos
communication example.
īExplains how LAN works .
īEthernet and switch how it works.
īCisco IOS commands.
08/02/13
Instructional Design-Computer Networking -
Bridges Educational Group