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2. Networking Basis

2. Networking Basis. 2. Networking Basis. 2.1 Default gateway, its use and packet routing 2.2 DNS and primary/secondary servers 2.3 Configuring a NIC with an IPv4 and IPv6 address 2.4 Network cables 2.5 Network speeds/modes 2.6 NIC LED status/Switch port LED status

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2. Networking Basis

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  1. 2. Networking Basis P.S.R.Peiris, Information technology Center, UoP

  2. 2. Networking Basis 2.1 Default gateway, its use and packet routing 2.2 DNS and primary/secondary servers 2.3 Configuring a NIC with an IPv4 and IPv6 address 2.4 Network cables 2.5 Network speeds/modes 2.6 NIC LED status/Switch port LED status 2.7 Direct Internet access 2.8 Need for a public IP or NAT 2.9 Internet access through a proxy

  3. Default Gateway • A Device on a network that serves as an access point to another network. A default gateway is used by a host when an IP packet’s destination address belongs to someplace outside the local subnet. • A router is a good example of a default gateway

  4. Default Gateway • Important to make IP routing work efficiently • Maintains knowledge of other networks in the larger network and how to reach them • Individual hosts are freed of the burden of having to maintain extensive and continuously updated knowledge about individual remote IP network segments • Only the router that acts as the default gateway needs to maintain this level of routing knowledge to reach other remote network segments in the larger internetwork

  5. DNS • Translates an Internet name (Such as www. pdn.ac.lk) into an IP address(192.248.40.19). • Many applications rely on the directory services that DNS provide to do this work. Web browsers, email programs, and file transfer programs use the names of remote systems. The DNS protocol allows these clients to make requests to DNS servers in the network for the translation of names to IP addresses. Applications can use the address to sent their messages. Without this directory lookup service, the internet would be almost impossible to use.

  6. DNS and primary/secondary servers • In general, domain names can work with only one name server - the primary DNS. However, practice has shown that a domain name needs to have at least two name servers assigned in order to be available at any time. In case there is a problem with the primary name server, the secondary name server will be able to answer the online request for a particular domain. This back-up requirement has turned into an accepted Internet standard that prevents domain names from going offline.

  7. Configuring a NIC with an IPv4 address

  8. Configuring a NIC with an IPv6 address

  9. Configuring a NIC with an IPv6 address

  10. Testing loop-back address, testing its own IP • Loopback address is a special IP number (127.0.0.1) that is designated for the software loopback interface of a machine. • Loopback interface has no hardware associated with it, and it is not physically connected to a network. • Loopback interface allows IT professionals to test IP software without worrying about broken or corrupted drivers or hardware.

  11. Testing loop-back address, testing its own IP • For IPv4, this class A network address is anything in the 127.x.x.x range. • For IPv6, the reserved loopback address is ::1 • You can also specify LOOPBACK as the host name

  12. Testing loop-back address, testing its own IP • Ping 127.0.0.1

  13. A successful ping request to 127.0.0.1 verify that • a computer's network interface card, • it's drivers, and • the operating system's TCP/IP implementation are operating perfectly.

  14. Reachability test to default gateway • Ping [ip-address of default gateway]

  15. Use of ipconfig command

  16. route command • Displays and modifies the entries in the local IP routing table. • Without parameters, route displays help.

  17. route command Syntax • route [-f] [-p] [Command [Destination] [maskNetmask] [Gateway] [metricMetric]] [ifInterface]]

  18. route command Parameters • -f : Clears the routing table of all entries that are not host routes If this is used in conjunction with one of the commands (such as add, change, or delete), the table is cleared prior to running the command.

  19. route command -p : When used with the add command, the specified route is added to the registry and is used to initialize the IP routing table whenever the TCP/IP protocol is started. By default, added routes are not preserved when the TCP/IP protocol is started. When used with the print command, the list of persistent routes is displayed. This parameter is ignored for all other commands.

  20. route command Command Purpose AddAdds a route ChangeModifies an existing route DeleteDeletes a route or routes PrintPrints a route or routes

  21. C:\>route

  22. Network Media • The channel over which a message travels

  23. Network cables

  24. Straight Cables

  25. Cross Cables

  26. Ethernet Most widely used LAN Technology The success of Ethernet is due to the following factors: • Simplicity and ease of maintenance • Ability to incorporate new technologies • Reliability • Low cost of installation and upgrade

  27. Ethernet, fast Ethernet, Gigabit Ethernet, 10GE • 10 Mbps - 10Base-T Ethernet • 100 Mbps - Fast Ethernet • 1000 Mbps - Gigabit Ethernet • 10 Gbps - 10 Gigabit Ethernet

  28. Types of Ethernet

  29. Network Modes • Half Duplex • Full Duplex • Auto

  30. Half Duplex • Communication that only allows one station to receive while the other station is transmitting

  31. Full Duplex • Communication that allows for receipt and transmission simultaneously. • There are no collisions with full duplex transmission.

  32. Auto • Choose common transmission parameters, such as speed, duplex mode, and flow control.

  33. Auto Negotiation Feature on NIC or Switch Port • An Ethernet procedure by which two connected devices choose common transmission parameters, such as speed, duplex mode, and flow control. • connected devices first share their capabilities regarding these parameters and then choose the highest performance transmission mode they both support. • In the OSI model, autonegotiation resides in the physical layer. 

  34. Network Speeds • Bandwidth is the primary measure of computer network speed • Bandwidth is the amount of data that passes through a network connection over time as measured in bits per second (bps) • Latency is another element that contributes to network speed. • The term latency refers to any of several kinds of delays typically incurred in processing of network data. A so-called low latency network connection is one that generally experiences small delay times, while a high latency connection generally suffers from long delays.

  35. Measuring Network Latency • Network tools like ping tests and traceroute measure latency by determining the time it takes a given network packet to travel from source to destination and back, the so-called round-trip time. • Round-trip time is not the only way to specify latency, but it is the most common.

  36. NIC LED status • Solid green:- card is either connected or receiving a signal • Green flashing:-data being sent or received • No light:-card may be bad, not connected properly, or that the card is not receiving a signal from the network • Amber:-indicate collisions

  37. Switch LED status • No Light:-No link • Solid green:- Link is up, but there is no activity on the link • Blinking green: Link has activity • Blinking green and amber:- Link is faulty • Solid amber:- Port is faulty or is disabled due to an error condition

  38. Direct Internet access • A way of connecting a computer to the Internet without using a commercial online service. • Direct Internet access can be purchased through an independent local or national Internet Service Provider (ISP).

  39. Need for a public IP or NAT • For a computer to communicate with other computers and Web servers on the Internet, it must have an IP address. • Theoretically, you could have 4,294,967,296 unique addresses (232). The actual number of available addresses is smaller (somewhere between 3.2 and 3.3 billion) • With the explosion of the Internet and the increase in home networks and business networks, the number of available IP addresses is simply not enough.

  40. However, because you cannot route private addresses over the Internet, and there are not enough public addresses to allow organizations to provide one to every one of their hosts, networks need a mechanism to translate private addresses to public addresses at the edge of their network that works in both directions. Without a translation system, private hosts behind a router in the network of one organization cannot connect with private hosts behind a router in other organizations over the Internet.

  41. Network Address Translation (NAT) •  Network Address Translation allows a single device, such as a router, to act as an agent between the Internet (or "public network") and a local (or "private") network. • This means that only a single, unique IP address is required to represent an entire group of computers

  42. NAT Terminology

  43. NAT Terminology • Inside local address - Usually not an IP address assigned by a RIR(Regional Internet Registry ) or service provider and is most likely an RFC 1918 private address. In the figure, the IP address 192.168.10.10 is assigned to the host PC1 on the inside network. • Inside global address - Valid public address that the inside host is given when it exits the NAT router. When traffic from PC1 is destined for the web server at 209.165.201.1, router R2 must translate the address. In this case, IP address 209.165.200.226 is used as the inside global address for PC1

  44. NAT Terminology • Outside global address - Valid public IP address assigned to a host on the Internet. For example, the web server is reachable at IP address 209.165.201.1 • Outside local address - The local IP address assigned to a host on the outside network. In most situations, this address will be identical to the outside global address of that outside device

  45. How NAT Works

  46. How NAT Works

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