Networking Basics

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A beginner-level , computer networking stuff :)

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Networking Basics

  1. 1. NETWORKING-BASICS <ul><li>Lokesh Walase ( TY-Comp, Coep)
  2. 2. [email_address]
  3. 3. GNU Free Documentation License
  4. 4. Version 0.1 </li></ul>
  5. 5. OK, but we are going for something different....
  6. 6. What is a Network ? <ul><li>Interconnection of devices ie printers , computers , telephones etc
  7. 7. “Physical Connectivity” among two or more devices </li></ul>
  8. 8. What is networking ? <ul><li>Communication between interconnected devices
  9. 9. TYPES : ( geographical scope ) </li><ul><li>LAN( Local Area Network ) ie within room, building or a university.
  10. 10. MAN( Metropolitian Area Network ) ie spans entire city.
  11. 11. WAN( Wide Area Network ) ie connects different cities, states , countries . </li></ul></ul>
  12. 12. What do I need to set up network ? <ul><li>Devices like computer , printers , telephones etc
  13. 13. NIC ( Network Interface Card ) : it “physically” attaches a computer to a network .
  14. 14. Media : 1.Hub( always “Broadcasting” ) </li><ul><li>2.Switch( 1 st “Broadcasting” & then “Unicasting” ) </li></ul></ul>
  15. 15. Requirements of network <ul>3.Routers( connects different networks ) <li>Cables are used to connect NIC with hub/switch/routers
  16. 16. For LAN we use CAT5 or CAT6 cables with RJ-45 connector ( Registered Jack ) </li></ul>
  17. 17. Ethernet NIC card & Ethernet Connector with RJ-45 connector
  18. 18. RJ-45 connector & Crimper
  19. 19. Hub & Switch
  20. 20. Addressing in Networking <ul><li>Two types of address exists : </li><ul><li>1.MAC address ie “Physical” Address ( 48 bit )
  21. 21. 2.IP address ie “Logical” Address ( Ipv4 is 32bit & Ipv6 is 128 bit) </li></ul><li>Right now Ipv4 is in use.
  22. 22. Command to find MAC & IP address is : “ifconfig” </li></ul>
  23. 23. Addressing in Networking <ul><li>MAC( Media Access Control ) address also called as : link-level addr, ethernet addr, station addr, H/W addr .
  24. 24. Each NIC is programmed at factory with unique MAC. .
  25. 25. 48-bits = </li><ul><li>Top 24 bits: vendor id
  26. 26. Bottom 24 bits: node id </li></ul></ul>
  27. 27. MAC address <ul><li>Website to check your MAC address :
  28. 28. http://www.coffer.com/mac_find/ </li></ul>
  29. 29. Ipv4 Addresses <ul><li>32 bit number ( 4-octets of 8bits ) - Expressed in “dotted-quad” notation, e.g. 164.112.128.1
  30. 30. Two types : </li><ul><li>1. Public
  31. 31. 2. Private </li></ul></ul>
  32. 32. Five Classes in Public IP <ul><li>Class A : </li><ul><li>8bits( Net ID) + 24bits( Host ID)= 32bits
  33. 33. Range : 0.x.y.z to 127.x.y.z
  34. 34. Total nodes in a network of type Class A is ( 2^7 )*(2^24-2) </li></ul></ul>
  35. 35. Five Classes in Public IP <ul><li>Class B : </li><ul><li>16bits( Net ID) + 16bits( Host ID)= 32bits
  36. 36. Higher 2bits are “10”
  37. 37. Range : 128.x.y.z to 191.x.y.z
  38. 38. Total nodes in a network of type Class B is ( 2^14)*(2^16-2) </li></ul></ul>
  39. 39. Five Classes in Public IP <ul><li>Class C : </li><ul><li>24bits( Net ID) + 8bits( Host ID)= 32bits
  40. 40. Higher 3 bits are “110”
  41. 41. Range : 192.x.y.z to 223.x.y.z
  42. 42. Total nodes in a network of type Class C is ( 2^21)*(2^8-2) </li></ul><li>Thus , Net-ID does work of “local router” . </li></ul>
  43. 43. Five Classes in Public IP <ul><li>Classes A,B,C support “unicasting” .
  44. 44. Class D : ( supports “multicasting” , group emails ) </li><ul><li>Higher 4 bits are (1110)
  45. 45. Range is (224).x.y.z to (239).x.y.z </li></ul><li>Class E : ( research & future purpose ) </li><ul><li>Higher 4 bits are (1111)
  46. 46. Range is (240).x.y.z to (253).x.y.z </li></ul></ul>
  47. 47. Lets see an example <ul><li>If IP addr of system = 78.65.76.88 , find its “net ID” , 1 st host , last host & “Directed Broadcast Address” ( DBA )
  48. 48. ANS: 78.0.0.0 , 78.0.0.1 , 78.255.255.254 , 78.255.255.255 ( in that order )
  49. 49. “DBA” is used if packet has to be transmitted to all systems in a network.
  50. 50. Make all “host ID” bits as “1” . </li></ul>
  51. 51. One More Example... <ul><li>If IP addr of system = 203.89.79.66 , find its “net ID” , 1 st host , last host & “Directed Broadcast Address” ( DBA )
  52. 52. ANS : 203.89.79.00 , 203.89.79.01 , 203.89.79.254 , 203.89.79.255 </li></ul>
  53. 53. Limited Broadcast Address <ul><li>It is 255.255.255.255 .
  54. 54. Used to send packet to all nodes within “same” network .
  55. 55. Till now all we saw was “2-level hierarchy”.
  56. 56. But what is actually used is “3-level heirarchy” , it has concept of “subnetting”. </li></ul>
  57. 57. Ranges of Private IP addr <ul><li>Till now all were “public”, now “private”IP's-
  58. 58. 1.)10.0.0.0 to 10.255.255.255 OR
  59. 59. 2.)172.16.0.0 to 172.31.255.255 OR
  60. 60. 3.)192.168.0.0 to 192.168.255.255.
  61. 61. Can you guess the class-type of each ??
  62. 62. NOTE: 1.) has only 1 network , 2.) has max 16 networks & 3.) has max 256 networks . </li></ul>
  63. 63. Need of NAT router <ul><li>Network Address Translation .
  64. 64. Agent between public & private network.
  65. 65. Hides entire IP addr space behind single /group of IP addr. </li></ul>
  66. 66. DHCP & DHCP server <ul><li>Computers on IP networks must be configured b4 communication.
  67. 67. For eg, they must be given IP addr , default route etc .
  68. 68. This could be done manually. But DHCP does this for us.
  69. 69. It is – Dynamic Host Control Protocol . </li></ul>
  70. 70. DHCP & DHCP server <ul><li>DHCP is controlled by a DHCP-server.
  71. 71. DHCP enabled on your computer means you are letting DHCP server assign a IP( from a defined range of nos. )
  72. 72. DHCP server assigns a device IP , subnet mask , default gateway . </li></ul>
  73. 73. DNS & DNS server <ul><li>Domain Name System
  74. 74. Std technology for managing names of websites & Internet domains .
  75. 75. DNS server is like look-up table.
  76. 76. Can you think of something similar that we already use ?? </li></ul>
  77. 77. DNS & DNS servers <ul><li>DNS servers communicate with each other using private protocols.
  78. 78. All DNS servers are arranged in heirarchy .
  79. 79. cat /etc/resolv.conf </li></ul>
  80. 80. Networking commands <ul><li>ifconfig: display current config for all NIC's
  81. 81. ifconfig eth0 down : disable network card
  82. 82. ifconfig eth0 up : enable network card
  83. 83. host moodle.coep.org.in : DNS test
  84. 84. traceroute www.whatismyip.com
  85. 85. tracepath www.whatismyip.com </li></ul>
  86. 86. Networking commands <ul><li>ping localhost : if error then NIC is not physically installed or is bad .
  87. 87. ping moodle.coep.org.in : check connection
  88. 88. netstat -rn : ?? </li></ul>
  89. 89. ssh & scp <ul><li>Ssh – secure shell , scp- secure copy.
  90. 90. Try this : ssh [email_address]
  91. 91. Try this : scp document.pdf [email_address] : ( send file at home folder of student )
  92. 92. Several combinations for scp at : http://www.examplenow.com/scp/ </li></ul>

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