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Networking Basics CCNA 1 Chapter 2

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  1. Networking Basics CCNA 1Chapter 2

  2. Networking Basics and Terminology A Brief History of the Networking Universe • Earliest commercial computers were large mainframes, run by computer scientists • Terminals were invented, allowing users to interact with the computers • Eventually (1960s), some terminals were located to allow remote access

  3. Networking Basics and Terminology A Brief History of the Networking Universe • By late 1960s minicomputers entered marketplace • “Mini’s” were smaller, less powerful and less expensive than mainframes • Mid 1970s – First personal computers (PCs) built by researchers

  4. Networking Basics and Terminology A Brief History of the Networking Universe • 1977 – Apple introduces the Apple-II • 1981 – IBM introduces its first PC • Mid 1980s – Computer users with standalone computers start sharing data through the use of modems connecting to another computer (dialup, point-to-point)

  5. Networking Basics and Terminology The Need for Networking Protocols and Standards • 1960s to 1980s – Each vendor set its own proprietary protocols and standards • Equipment from different vendors would not interoperate • Eventually, open standards were agreed upon • Open standards allow more competition, which increases speed of development

  6. Networking Basics and Terminology Popular Network Standards Organizations

  7. Networking Basics and Terminology Ethernet LANs and LAN Devices • Ethernet LANs originally used coaxial cable (similar to Cable TV cable) • Network Interface Cards (NICs) would attach to a length of cable called a segment

  8. Networking Basics and Terminology Ethernet LANs and LAN Devices • In early Ethernet LANs, all devices sent their data on one wire • All other devices on the segment received the signal • These types of Ethernet are said to be “broadcast” media, because any signal sent by one device is received by all other devices

  9. Networking Basics and Terminology Characteristics of Early Ethernet LANs • Limited to a relatively small geographic area • Allows multiple devices access to high-speed media • Administrative control rests within a single company • Provides full-time connectivity • Typically connects devices that are close together

  10. Networking Basics and Terminology Cisco Networking Device Icons

  11. Networking Basics and Terminology Ethernet Repeaters • When a signal is sent over a wire, it degrades • 10BASE5 limited a single segment to 500 meters; 10BASE2 to a little less than 200 meters (185 meters) – hence their names (the 5 and the 2; the 10 is for 10Mbps) • To extend the distance of LANs, repeaters were developed

  12. Networking Basics and Terminology Features of Ethernet Repeaters • Typically had two ports connecting two different Ethernet segments • Interpreted the incoming signal on one port as 1’s and 0’s • Sent a regenerated clean signal out the other port

  13. Networking Basics and Terminology Repeated Ethernet Signal See Conceptual View on next slide • Betty sends a clean signal • The signal degrades by the time it reaches the repeater • The repeater regenerates a new, clean signal and sends it out its other port

  14. Networking Basics and Terminology Repeated Ethernet Signal

  15. Networking Basics and Terminology Ethernet Hubs and 10BASE-T • Coax cables were expensive and difficult to work with • If the cable broke, everyone on the LAN had problems • Lead to the creation of 10BASE-T

  16. Networking Basics and Terminology Ethernet Hubs and 10BASE-T • The 10 means it runs at 10Mbps • The T means that it uses twisted-pair cable • The cable is Unshielded Twisted-Pair (UTP), which is cheaper than coax cable • Smaller diameter than coax cable • Terminated with RJ-45 connectors

  17. Networking Basics and Terminology 10BASE-T with a Hub – Star Topology

  18. Networking Basics and Terminology Functions of a Hub • Provides RJ-45 jacks so cables with RJ-45 connectors can be attached • Repeats any incoming signal out all other ports • Was originally called a “multiport repeater”

  19. Networking Basics and Terminology Ethernet Bridges • Examine incoming signal, interpret signal as 0’s and 1’s, find the destination MAC address listed in the frame • If destination MAC address is reachable via a different interface than the one on which it was received, then clean, regenerate and forward the frame out that interface • If the destination is reachable on the same interface on which it was received, discard the frame (this is called “filtering”)

  20. Networking Basics and Terminology A Bridge Making a Filtering Decision

  21. Networking Basics and Terminology A Bridge Making a Forwarding Decision

  22. Networking Basics and Terminology Ethernet Frames • An Ethernet frame is the data sent by an Ethernet NIC or interface • The first bits sent are the header; contains info such as the destination and source MAC addresses • Includes headers from other protocols, such as IP

  23. Networking Basics and Terminology Conceptual View of an Ethernet Frame

  24. Networking Basics and Terminology Unicast and Broadcast Ethernet Frames and Addresses • Before the introduction of bridges, the LAN acted as a broadcast medium • The term unicast MAC address identifies a single NIC or Ethernet interface • Sometimes a computer needs to send a frame that will reach all devices on the LAN; it uses a broadcast address: FFFF.FFFF.FFFF • All devices must process data sent to this address

  25. Networking Basics and Terminology LAN Switches • Like a hub, a switch provides a large number of ports/jacks to plug in cables • Forms a physical star topology • When forwarding a frame, the switch regenerates a clean signal • Like bridges, switches use the same filtering/forwarding logic on a per-port basis

  26. Networking Basics and Terminology A Switch Making a Forwarding Decision

  27. Networking Basics and Terminology Wide-Area Networks (WANs) • Cover a large geographic area • WAN Technologies: • Modems • Integrated Services Digital Network (ISDN) • Digital Subscribe Line (DSL) • Frame Relay • T1 or E1 leased lines – T1, E1, T3, E3, etc. • Synchronous Optical Network (SONET) – synchronous transport Level 1(STS-1) optical carrier [OC]-1, STS-3 (OC-3), etc.

  28. Networking Basics and Terminology Point-to-Point Leased Lines • A point-to-point leased line extends between two locations • The line is not owned by the user; it is leased from a service provider • The service provider is often a telephone company (telco) • Often, the term link is used to describe a point-to-point leased line

  29. Networking Basics and Terminology Point-to-Point Leased Lines: Leased lines are drawn like lightning bolts

  30. Networking Basics and Terminology Routers and Their Use with LANs • Routers perform a basic but very important forwarding process in which they receive data packets and then forward the packets toward the destination • Routers can send and receive traffic on most any kind of physical networking media • Routers are the perfect device to connect a LAN to a WAN

  31. Networking Basics and Terminology Metropolitan Area Networks (MANs) • A medium-sized network geography, perhaps city-wide • Usually very high speed • Optical media used between routers can move data at 10 Gbps or even 40 Gbps

  32. Networking Basics and Terminology High-Speed City-Wide MAN

  33. Networking Basics and Terminology Storage-Area Networks (SANs) • Allow computers to communicate with storage devices • Features of SANs: • Performance: concurrent access of disk or tape arrays • Availability: used to back up data to offsite locations • Scalability: easy relocation of backup data, operations, file migration, and data replication between systems

  34. Networking Basics and Terminology Typical SAN Used by a Server Farm

  35. Networking Basics and Terminology Virtual Private Networks (VPNs) • Companies can use the Internet to send data between sites, instead of using leased lines • Often less expensive than leased lines • Can be less secure than leased lines

  36. Networking Basics and Terminology Virtual Private Networks (VPNs)

  37. Networking Basics and Terminology Intranet VPNs • Packets are encrypted before they leave for the Internet • Not practical for a hacker to break the encryption • Intranet VPNs are used inside a single organization

  38. Networking Basics and Terminology Intranet VPN

  39. Networking Basics and Terminology Comparing Intranet VPNs to Extranet and Access VPNs • Intranet VPN – A VPN between sites of a single organization • Extranet VPN – A VPN between sites of different organizations • Access VPN – A VPN between individual users and an enterprise network, allowing access while working from home or traveling

  40. Networking Basics and Terminology Extranet and Access VPNs

  41. Networking Basics and Terminology Physical Network Topologies

  42. Networking Basics and Terminology Physical Bus Topology • 10BASE2 and 10BASE5 use a bus topology • Looks like a city street where each of the computers is a bus stop • A frame sent by one device is received by all other devices

  43. Networking Basics and Terminology Physical Star Topology • 10BASE-T Ethernet connects with a hub • The hub is the device at the center, so it resembles a start • The actual physical layout of the cable may not be in a star pattern

  44. Networking Basics and Terminology Logical Bus Topology • “Logical” refers to how the network operates, not where the cables run • 10BASE-T is a logical bus, because all devices see any signal sent by other devices on the network

  45. Networking Basics and Terminology Physical versus Logical Topology • Physical Topology – The topology is determined by the physical layout of the cabling and transmission media • Logical Topology – The topology is determined by the media access control logic and how the devices collectively send traffic over the network

  46. Networking Basics and Terminology Typical Modern LAN and Its Similarities to a Star Topology

  47. Networking Basics and Terminology Typical Modern LAN Design for a Single Building

  48. Networking Basics and Terminology Ring Topologies • Cable is installed from first device to second device, second device to third device, and so on, until the last device connects to the first device • Each device cleans up the signal, so fewer repeaters are needed • Can have single or dual rings

  49. Networking Basics and Terminology Ring Topology • R1 and R2 detect that cable between them is cut • R1 and R2 loop the primary ring to the backup ring using circuitry in the routers • One ring still works, assuring connectivity

  50. Networking Basics and Terminology Hierarchical and Extended Star Topologies • A central device or site connects to several other sites • Much like a star topology • The other sites then connect to still more sites • Extended star topologies have the same features as a hierarchical topology, but are not drawn in a hierarchy