Networking 101

Copyright Priscilla Oppenheimer

Lab 6 LAN Optimization

Scenario

You are a network administrator working for a large company. The network engineers at headquarters have sent you some Cisco routers, firewalls, and switches to install. The devices are already configured. Your college intern has installed the cables. Your job is to check the intern's and engineers' work and to determine if there is any optimization that can be done. For example, could you use 100 Mbps instead of 10 Mbps? Could you use full duplex instead of half duplex?

Step 1. Check the Physical and Data Link Layers.

  1. Power on the routers, firewalls, switches, and workstations if they aren't already on.
  2. Check the Physical Layer by insuring that there is a link light for all connections.
  3. For an additional check of the Physical and Data Link Layers, open a "management session" for a router, firewall, or switch using HyperTerminal. HyperTerminal settings are as follows:
    1. Bits per second = 9600
    2. Data bits = 8
    3. Parity = None
    4. Stop bits = 1
    5. Flow control = none.
  4. Type enable (followed by a carriage return). Type the enable password, provided by the instructor.
  5. Type show interface. Verify that for each interface you see output similar to this: "Ethernet 1/0 is up, line protocol is up."
  6. Verify that the reliability (rely) is 255/255 and that the txload and rxload are not 255/255.
  7. Record the number of CRC errors
  8. On the Ethernet interfaces, record the number of collisions, including the number of late collisions.
  9. Determine whether the Ethernet interfaces are using 10 or 100 Mbps.
  10. Determine whether the Ethernet interfaces are using full or half duplex.

Step 2. Check Throughput

  1. Get a baseline measurement of throughput before we upgrade anything.
    1. Try downloading a large file or going to http://www.dslreports.com/stest.
    2. Record the throughput in Kbps or KB per second.

Step 3. Upgrade to 100 Mbps and Full Duplex if Possible

  1. In this step, we will try upgrading from 10 half to 100 full, only on the links that should support this. So, for each link that should support 100 full, follow the correct set of steps below, depending on which device you are on.
  2. PIX instructions:
    1. In HyperTerminal type configure terminal, which means you are configuring the device from a terminal. (The PC acts as a terminal.)
    2. Type interface, e (for Ethernet) and the number of the interface (1 or 0), followed by 100full.
      1. For example, to change interface e0, type interface e0 100full.
    3. Type exit to get out of configuration mode.
  3. Switch instructions:
    1. In HyperTerminal type configure terminal, which means you are configuring the device from a terminal. (The PC acts as a terminal.)
    2. Type interface, fa (for Fast Ethernet) and the number of the interface.
      1. For example, to change interface fa0/1, type interface fa0/1.
    3. Press Enter.
    4. Change the speed with the speed command. (Use a question mark to see the allowed parameters.)
    5. Change the duplex with the duplex command. (Use a question mark to see the allowed parameters.)
    6. Type exit to get out of configuration mode.
  4. Router instructions:
    1. In HyperTerminal type configure terminal, which means you are configuring the device from a terminal. (The PC acts as a terminal.)
    2. Type interface e (for Ethernet) or fa (for Fast Ethernet) and the number of the interface.
      1. For example, to change interface fa 0/0, type interface fa0/0.
    3. Press Enter.
    4. Change the speed with the speed command. (Use a question mark to see the allowed parameters.)
    5. Change the duplex mode with the full-duplex command.
    6. Type exit to get out of configuration mode.
  5. PC instructions:
    1. Get into the Network Connections Control Panel by selecting Start>Settings>Network Connections.
    2. Double click on Local Area Connection.
    3. Go into Properties.
    4. Click on Configure for the Ethernet adapter.
    5. Click on the Advanced tab and scroll down to Link Speed & Duplex.
    6. Try using 100 Mbps/Full Duplex instead of the current configuration.

Step 4. Test your new configuration.

  1. Run another throughput test to see if you get better throughput.
  2. Verify that errors have not increased by checking the output of show interface for the interfaces you changed.

Step 5. Learn from your mistakes in a lab before you get into the "real world!" :-)

  1. Try setting 100 Mbps and full duplex on links that theoretically shouldn't support it (for example on a link that connects a hub.)
  2. Determine whether collisions and late collisions increase by checking the output of show interface on the routers or firewalls.

Reflection

What were the work goals of this project? (Please write this as if you were writing a work status report. In other words, write the project goals, not the learning objectives.) ___________________________________________________________________________________________________________________

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What problems, if any, occurred when upgrading the speed and duplex mode on links that should support an upgrade? ___________________________________________________________________________________________________________________

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What problems occurred when upgrading the speed and duplex mode on links that shouldn't support an upgrade?

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