CompNtwk : Lab 1.4.6A Gaining Physical Access to the Network

Task 1: Access and Change the Router Passwords

Step 1: Attempt login to the router

NOTE: If the PC used in this lab is also connected to your Academy LAN or to the Internet, ensure that you record the cable connections and TCP/IP settings so these can be restored at the conclusion of the lab.

  1. Referring to the Topology 1, connect the host PC NIC Ethernet port to the router Fa0/0 Ethernet port using a crossover cable. Ensure that power has been applied to both the host computer and router.
  2. Using the given preconfigured topology, attempt to telnet to the router from the PC command line.
  3. When this attempt at remote login fails, establish a direct physical connection to the router by making the necessary console connections between the PC and router. Then establish a terminal session using HyperTerminal or TeraTerm. What does the message-of-the-day display? Jawaban:  ONLY AUTHORIZED ACCESS TO THIS DEVICE PERMITTED Unauthorized access will be penalized in accordance with the relevant laws

Attempt to log in by guessing the password.

How many login attempts are allowed? __________ 3

What message is displayed to indicate failure of the log-in attempts? Jawaban: % Bad passwords

The configuration register needs to be changed so that the startup-configuration is not loaded. Normally, this is this done from the global configuration mode, but because you cannot log in at all, the boot process must first be interrupted so that the change can be made in the ROM Monitor mode.

Step 2: Enter the ROM Monitor mode

ROM Monitor mode (ROMMON) is a limited command-line environment used for special purposes, such as low-level troubleshooting and debugging. ROMMON mode is invoked when a Break key sequence sent to the console port interrupts the router boot process. This can only be done via the physical console connection.

The actual Break key sequence depends on the terminal program used:

  • • With HyperTerminal, the key combination is Ctrl+Break.
  • • For TeraTerm, it is Alt+b.

The list of standard break key sequences is available athttp://www.cisco.com/warp/public/701/61.pdf

  1. To enter ROM Monitor mode, turn the router off, wait a few seconds, and turn it back on.
  2. When the router starts displaying “System Bootstrap, Version …” on the terminal screen, press the Ctrl key and the Break key together if using HyperTerminal, or the Alt key and the b key together if using TeraTerm.

The router will boot in ROM monitor mode. Depending on the router hardware, one of several prompts such as “rommon 1 >” or simply “>” may show.

Step 3: Examine the ROM Monitor mode help

Enter ? at the prompt. The output should be similar to this:

rommon 1 > ?

alias set and display aliases command

boot boot up an external process

break set/show/clear the breakpoint

confreg configuration register utility

context display the context of a loaded image

dev list the device table

dir list files in file system

dis display instruction stream

help monitor builtin command help

history monitor command history

meminfo main memory information

repeat repeat a monitor command

reset system reset

set display the monitor variables

sysret print out info from last system return

tftpdnld tftp image download

xmodem x/ymodem image download

Step 4: Change the configuration register setting to boot without loading configuration file

From the ROM Monitor mode, enter confreg 0×2142 to change the config-register. rommon 2 >confreg 0×2142

NOTE: The ROMMON prompt increments when a command is issued – this is normal behavior. The increment does not mean a change of mode. The same ROMMON commands are still available. “0x” (zero- x) denotes that 2142 is a hexadecimal value. What is this value in binary?

Step 5: Restart router

  1. From the ROM Monitor mode, enter reset, or power cycle the router. rommon 3 > reset

Due to the new configuration register setting, the router will not load the configuration file. After restarting, the system prompts:

“Would you like to enter the initial configuration dialog? [yes/no]:”

  1. Enter no and press Enter.

Step 6: Enter Privileged EXEC mode and view and change passwords

The router is now running without a loaded configuration file.

  1. At the user mode prompt Router>, enter enable and press Enter to go to the privileged mode without a password.
  2. Use the command copy startup-config running-config to restore the existing configuration. Because the user is already in privileged EXEC, no password is needed.
  3. Enter show running-config to display the configuration details. Note that all the passwords are shown.

enable password different

line con 0 password unusual

line vty 0 4 password uncommon

What two measures could be taken to prevent the passwords from being readable? service password encryption, enable secret somepassword

  1. If the passwords were not readable, they can be changed. Enter configure terminal to enter the global configuration mode.
  2. In global configuration mode, use these commands to change the passwords:

FC-CPE-1(config)#enable password cisco

FC-CPE-1(config)#line console 0

FC-CPE-1(config-line)#password console

FC-CPE-1(config-line)#login

FC-CPE-1(config-line)#line vty 0 4

FC-CPE-1(config-line)#password telnet

FC-CPE-1(config-line)#login

Step 7: Change the configuration register setting to boot and load the configuration file

  1. The instructor will provide you with the original configuration register value, most likely 0×2101. While still in the global configuration mode, enter config-register 0×2101 (or the value provided by your instructor). Press Enter. FC-CPE-1(config)#config-register 0×2101
  2. Use the Ctrl+z combination to return to the privileged EXEC mode.
  3. Use the copy running-config startup-config command to save the new configuration.
  4. Before restarting the router, verify the new configuration setting. From the privileged EXEC prompt, enter the show version command and press Enter.
  5. Verify that the last line of the output reads: Configuration register is 0×2142 (will be 0×2101 at next reload).
  6. Use the reload command to restart the router.

Step 8: Verify new password and configuration

  1. When the router reloads, log in and change mode using the new passwords.
  2. Issue the no shutdown command on the fa0/0 interface to bring it up to working status. FC-CPE-1(config-if)# no shutdown
  3. Save the running configuration to startup configuration FC-CPE-1# copy run start
  4. Disconnect the console cable and access the router using Telnet from the PC command line. The newly configured passwords will allow a successful login.

Step 9: Clean up

Erase the configurations and reload the router. Disconnect and store the cabling. For PC hosts that are normally connected to other networks (such as the school LAN or to the Internet), reconnect the appropriate cabling and restore the TCP/IP settings.

Task 2: Access and Change the Switch Passwords

Step 1: Attempt login to the switch

NOTE: If the PC used in this lab is also connected to your Academy LAN or to the Internet, ensure that you record the cable connections and TCP/IP settings so these can be restored at the conclusion of the lab.

  1. Referring to the Topology 2, connect the host PC NIC Ethernet port to the switch Fa0/1 Ethernet port using a straight-through cable. Ensure that power has been applied to both the host computer and switch.
  2. Using the given preconfigured topology, attempt to telnet to the router from the PC command line.

Step 2: Enter the switch: mode

  1. Power off the switch.
  2. Locate the MODE button on the front of the switch.
  3. Hold down the MODE button on the front of the switch while powering on the switch. Release the

MODE button after 10 seconds.

Output similar to the following should be displayed:

Base ethernet MAC Address: 00:0a:b7:72:2b:40

Xmodem file system is available.

The password-recovery mechanism is enabled.

The system has been interrupted prior to initializing the

flash files system. The following commands will initialize

the flash files system, and finish loading the operating

system software:

flash_init

load_helper

boot

switch:

  1. To initialize the file system and finish loading the operating system, enter the following commands at

the switch: prompt:

switch: flash_init

switch: load_helper

  1. To view the contents of flash memory, enter dir flash: at the switch: prompt.

switch: dir flash:

NOTE: Do not forget to type the colon (:) after the word “flash” in the command dir flash:

The file config.txt should be seen listed.

  1. Enter rename flash:config.text flash:config.old to rename the configuration file. This file contains the password definitions.
  2. Enter dir flash: at the switch: prompt to view the name change. switch: dir flash:

Step 3: Restart the switch

  1. Enter boot to restart the switch.
  2. Would you like to terminate autoinstall? [Yes]: Y
  3. Would you like to enter the initial configuration dialog? [yes/no] N Switch>

Step 4: Enter Privileged EXEC mode and view and change passwords

The switch is now running without a loaded configuration file.

  1. At the user mode prompt Router>, type enable and press Enter to go to the privileged mode without a password.
  2. Enter rename flash:config.old flash:config.text to rename the configuration file with its original name.

Switch#rename flash:config.old flash:config.text

Destination filename [config.text]?

Press Enter to confirm file name change.

  1. Copy the configuration file into RAM.

Switch#copy flash:config.text system:running-config

Destination filename [running-config]?

Press Enter to confirm file name.

  1. Press Enter to accept the default file names.

Source filename [config.text]?

Destination filename [running-config]

The configuration file is now loaded.

  1. Enter show running-config to display the configuration details. Note that all the passwords are shown.

enable password different

line con 0 password unusual

line vty 0 4 password uncommon

What two measures could be taken to prevent the passwords from being readable?

____________________________________________ service password encryption

____________________________________________ enable secret somepassword

  1. If the passwords were not readable they can be changed. Enter configure terminal to enter the global configuration mode.
  2. Change the unknown passwords.

FC-ASW-1#configure terminal

FC-ASW-1(config)#enable password cisco

FC-ASW-1(config)#line console 0

FC-ASW-1(config-line)#password console

FC-ASW-1(config-line)#line vty 0 15

FC-ASW-1(config-line)#password telnet

FC-ASW-1(config-line)#exit

FC-ASW-1(config)#exit

Step 5: Save the configuration file

Use the copy running-config startup-config command to save the new configuration.

Step 6: Verify new password and configuration

Power cycle the switch and verify that the passwords are now functional.

Step 7: Clean up

Erase the configurations and reload the switch. Disconnect and store the cabling. For PC hosts that are normally connected to other networks (such as the school LAN or to the Internet), reconnect the appropriate cabling and restore the TCP/IP settings.

Task 3: Reflection

Consider the different methods of securing physical access to networking devices such as routers and

switches. List how only those people who require access can be identified and how this security can be

implemented. Jawaban: Physical security includes locking rooms and closets containing switches and routers. Networking devices sharing common space with other services, such as electrical power panels, should be enclosed in a separated lockable cabinet. Keys and access codes should only be given to identified authorized personnel. People authorized to access the networking devices should include only those network personnel required to configure and troubleshoot switches and routers as part of their regular or daily duties. Other IT personnel such as help desk staff, data center administrators, or desktop support workers would normally not be required to access switches and routers.

 

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