CCNA

1. Cisco Network Support Certifications 2. Networking Terms 3. INTRODUCTION TO NETWORKING 4. TYPES OF NETWORK 5. The Development of the Internet 6. NETWORK ARCHITECTURE 7. TOPOLOGY 8. BUS TOPOLOGY 9. RING TOPOLOGY 10. STAR TOPOLOGY 11. MESH TOPOLOGY 12. HYBRID TOPOLOGY 13. Speed of Networking device 14. NETWORK DEVICES 15. Exploring Wireless Network 16. REPEATERS 17. HUB 18. SWITCH 19. BRIDGE 20. ROUTERS 21. TRANSMISSION Telecommunication 22. Difference between Full Duplex, Half Duplex and Simplex 23. IP-ADDRESSING and IPV4 24. IPv4 address classes 25. IPV6 [ Internet Protocol Version 6 ] 26. SPEED OF VARIOUS DEVICES 27. Network Security 28. Some basic suggestion and steps to prevent Attacks and Network security 29. OSI model 30. UPPER and LOWER Layer 31. Application Layer (Layer 7) 32. Presentation Layer (Layer 6) 33. Session Layer (Layer 5) 34. Transport Layer (Layer 4) 35. Network Layer (Layer 3) 36. Data Link Layer 2 37. Physical Layer 1 38. TCP/IP The DoD Model 39. ROUTED PROTOCOL 40. Ports and Application 41. Important Application, Protocol and Port Number 42. Router Function 43. Types of Routing Protocols 44. STARTING ROUTER 45. CISCO IOS 46. Logging in to the Router 47. CISCO Router IOS commands List 48. Setting time and date of router 49. Router configuration commands 50. Optimizing Switch and Router 51. Understanding Router Terms 52. ROUTER SECURITY 53. Configuring CISCO SWITCH Security Policy 54. IMPLEMENTING STATIC ROUTING 55. UNDERSTANDING THE NEED FOR NAT 56. WAN Connections 57. Access List [ACL] 58. VLAN [Virtual Local Area Network] 59. SPANNING TREE :- BROADCAST STORM 60. Lab 1 Setting up a Serial Interface 61. Lab 2 : IP Addressing 62. Lab 3 Static Routes 63. Lab 4 Default Routes 64. Lab 5 RIP Routes 65. Lab 6 IGRP Routes 66. Lab 7 EIGRP Routes 67. Lab 8 OSPF Routes 68. Lab 9 CHAP and RIP 69. Lab 10 Standard Access-Lists with RIP 70. Lab 11 Extended Access-Lists with RIP 71. Lab 12 Static NAT 72. Lab 13 Many to One NAT 73. Lab 14 NAT Pool 74. Lab 15 ( 2950 Trunk ) 75. Lab 16 ( 2950 Trunk Dynamic ) 76. Lab 17 (2950 VLANs) 77. Lab 18 ( 2950 Deleting VLANs ) 78. Lab 19 ( 2950 VTP ) 79. Lab 20 ( 2950 VTP w/ client ) 80. Lab 21 ( 2950 Telnet )
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UNDERSTANDING THE NEED FOR NAT tutorials

  • Internet is very big network, hundreds and thousands of networks with servers and routers etc.

  • There are many devices, so as on date we run out of IP addresses i.e. using IPV4

  • NAT allows multiple devices to share an internet IP Address.

  • When you access internet using private ip addresses assigned to your NIC cards, when you connect to internet using private ip address router cannot move it outside because private IP address are not routable.

  • So it has to assign you some public IP address.

 

Inside address

Outside address

192.168.1.2 : 5432

200.1.1.1 : 5432

192.168.1.3 : 3146

200.1.1.1 : 3146

 

  • Letís assume your network have private ip address of 192.168.1.2 & 3Ö.and so on. When you uses internet to browse site, Windows web browser will generate unique source port no. letís say in our case it is 5432. It send it to router. What NAT does it will transfer date outside using public address by maintaining source port i.e. 200.1.1.1 : 5432. Inside router it maintain NAT table.

  • Therefore if 2 PCs browse internet at same time, both will send its private ip address i.e. 192.168.1.2 : 5432 and 192.168.1.3 : 3146. From Cisco router it will use 200.1.1.1 only but with 5432 and 3146 source port. And thatís why there is no problem in maintaining session.

  • There are 0 to 65,535 source port no total that can be manage by router. And this form of NAT is commonly called PAT [Port Address Translation]

  • On router

 

Show ip nat translations

 

  • After some time if you give above command some of the session will close

 

Show ip nat translations


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