Chapter 3 - Lesson 2 - PPT


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Chapter 3 - Lesson 2 - PPT

  1. 1. Network Devices Lecture 2
  2. 2. Cabling <ul><li>Computer to computer – crossover cable </li></ul><ul><li>Computer to hub – straight-through cable </li></ul><ul><li>Hub to switch or Hub to hub </li></ul><ul><ul><li>MDI-X port to MDI port – straight-through </li></ul></ul><ul><ul><li>MDI port to MDI-X port – straight-through </li></ul></ul><ul><ul><li>MDI-X port to MDI-X port – cross-over </li></ul></ul>
  3. 3. LEDs <ul><li>Light emitting diodes </li></ul><ul><li>Present on both hubs, switches, and routers </li></ul><ul><li>Green – live connection at that port on that piece of equipment </li></ul><ul><li>Flashing green – activity (traffic) </li></ul><ul><li>Amber – problem </li></ul><ul><li>Red or no light – not working </li></ul>
  4. 4. Managed v. Unmanaged <ul><li>Applies to both switches and hubs </li></ul><ul><li>Has an interface that can be configured </li></ul><ul><ul><li>Speed </li></ul></ul><ul><ul><li>VLANS (switches) </li></ul></ul>
  5. 5. Number of Ports <ul><li>Hubs and Switches </li></ul><ul><ul><li>8 </li></ul></ul><ul><ul><li>16 </li></ul></ul><ul><ul><li>24 </li></ul></ul><ul><ul><li>32 </li></ul></ul>
  6. 6. Packet Network Header Data The protocol data unit that is transmitted over a WAN or between LANs when using a router.
  7. 7. IP Address <ul><li>Logical Address or Network Address </li></ul><ul><li>#.#.#.# </li></ul>
  8. 8. Routers <ul><li>Intelligent network device </li></ul><ul><li>Has CPU built in </li></ul><ul><li>Determines best path for packet to get to destination </li></ul><ul><li>Bases decision on IP address </li></ul><ul><ul><li>Synonyms – logical address, network address </li></ul></ul><ul><li>Refers to its routing table to make decisions about which port to send the packet </li></ul><ul><li>Configurable </li></ul><ul><li>Can connect two LAN segments </li></ul><ul><li>Can connect a LAN to a WAN </li></ul>AUI ports – notice the transceivers on the second router on the rack. Serial ports to connect LAN to WAN
  9. 9. Routable (Routed) Protocols <ul><li>Responsible for sending messages between nodes. </li></ul><ul><li>IP – Internet Protocol (part of the TCP/IP protocol suite </li></ul><ul><li>IPX/SPX – Novell – going away; replaced by IP </li></ul><ul><li>Appletalk – MacIntosh – replaced by IP </li></ul>
  10. 10. NetBeui <ul><li>This network protocol is non-routable. </li></ul>
  11. 11. Routing Protocols <ul><li>Routing protocols route routable protocols </li></ul><ul><li>Responsible for updating routing tables between routers so they can know the topology of the network and determine best path. </li></ul><ul><ul><li>Routing tables – lists of networks and the associated port to each network </li></ul></ul><ul><li>Routing can be dynamic (automatic) or administrator can configure a static route. </li></ul>
  12. 12. Routing Table Example Network Interface E0 E1 S0 S0 Network E1 Network Network E0
  13. 13. Routing Protocols <ul><li>Distance Vector </li></ul><ul><li>Link State </li></ul>
  14. 14. Distance Vector <ul><li>Routers send routing table updates to each neighboring router periodically. </li></ul><ul><li>Examples </li></ul><ul><ul><li>RIP (Routing Information Protocol) </li></ul></ul><ul><ul><li>IGRP (Interior Gateway Routing Protocol) </li></ul></ul><ul><li>Movement from one router to the next is considered a “hop.” </li></ul><ul><li>DV metric (measurement) is “hops.” </li></ul><ul><li>Lower number of hops is better – determines best path </li></ul>
  15. 15. DV Disadvantage <ul><li>Each router transmits its entire routing table every 30 seconds (RIP) creating a lot of network traffic. </li></ul>
  16. 16. Convergence <ul><li>The amount of time needed for all routers in a network to have common knowledge – routing tables all have the same information in them. </li></ul>
  17. 17. Routing Loops A C D E B Network 1 At first, all routers have common routing tables. Network 1 goes down. Router E sends its routing table without Network 1. Router A updates its routing table. At the next update (after 30 seconds), Router A sends its table to D and B. They have to update their tables. Meanwhile, Router C doesn’t have the update about Network 1 so it sends its table to D & B. D may assume that there’s another path through C -> B to Network 1 so it updates its table. Next round, it updates Router A. Router A assumes there is another path. Now they all have inaccurate information and the loop continues.
  18. 18. Split Horizon A C D E B Network 1 Split horizon will not allow an update from the opposite direction of the first update. So, A notified D and B and they cannot send erroneous tables back to A thereby preventing routing loops.
  19. 19. Link State Protocols <ul><li>Examples </li></ul><ul><ul><li>OSPF – Open Shortest Path First </li></ul></ul><ul><ul><li>NLSP – Network Link State Protocol </li></ul></ul><ul><li>When network is installed and OSPF configured as the routing protocol, OSPF uses LSAs (Link State Advertisements) to collect information about the network and build a database of the entire topology. </li></ul><ul><li>During the initial stage where it is learning the topology, the process causes a lot of activity on the network. After the database is built and best paths chosen, traffic is minimized because updates only occur when there is a topology change, (for example, a network goes down) and LSAs are exchanged to make the update in the database. </li></ul><ul><li>Disadvantage </li></ul><ul><ul><li>Requires more RAM to store the database than DV protocols. </li></ul></ul>
  20. 20. Server-based Routers <ul><li>Servers can have two NICS installed and act as a limited router. </li></ul>
  21. 21. Brouter <ul><li>Device that can function as both a router and a bridge depending upon the protocol of the message. If it is a routable protocol, it routes it. If the message protocol is an Ethernet protocol, it either forwards it or blocks it (functions as a bridge). </li></ul>
  22. 22. Gateways <ul><li>A device, system, or software that can perform the function of translating data from one protocol to another (TR to Ethernet), and one format to another. </li></ul><ul><li>Usually a server. </li></ul><ul><li>Slows network traffic because of translation time. </li></ul>
  23. 23. CSU/DSUs <ul><li>Channel Service Unit/Digital Service Unit </li></ul><ul><li>Changes signal from one digital format to another. </li></ul>
  24. 24. ISDN Terminal Adapters <ul><li>Translates digital signal between two digital formats. </li></ul>
  25. 25. Modem <ul><li>Mo dulator/ Dem odulator </li></ul><ul><li>Translates from digital to analog and back. </li></ul><ul><li>56 kbps maximum connection speed. Actual transfer speed is less – around 43 kbps. </li></ul>
  26. 26. Two Factors that Determine Modem Connection Speed <ul><li>Maximum connection speed of the Universal Asynchronous Receiver/Transmitter (UART) chip </li></ul><ul><li>Actual modem speed </li></ul>
  27. 27. UART Chips & Speeds <ul><li>Chip Speed bps </li></ul><ul><li>8250 9600 </li></ul><ul><li>16450 115200 </li></ul><ul><li>16550 115200 </li></ul><ul><li>16650 430800 </li></ul><ul><li>16750 921600 </li></ul><ul><li>16950 921600 </li></ul>
  28. 28. Modem Commands to Know <ul><li>ATA – Answers incoming call </li></ul><ul><li>ATH – Hangs up current connection </li></ul><ul><li>ATZ – Resets the modem </li></ul><ul><li>ATI3 – Displays modem id info </li></ul>