The following three examples demonstrate the use of several boot system commands to specify the Cisco IOS software rescue boot sequence.
2-Network server
If the flash memory is damaged, a system image can be loaded from a TFTP server.
3-ROM
If the flash memory is damaged and the network server fails to load the image, booting from the ROM is the software's last bootstrap option. The system image stored in ROM contains some line command
The copy running-config startup-config command saves commands to NVRAM. The router will execute, if necessary, boot system commands in the order in which they were initially entered into configuration mode
4-Troubleshooting an iOS boot failure:
There are several things that can cause a router to boot poorly:
the configuration file has a missing or incorrect boot system statement.
A value in the configuration registry is incorrect.
the flash image is corrupted,
hardware failure.
5-Managing configuration files using TFTP:
In a Cisco router, the configuration is loaded into RAM and the boot configuration is stored in NVRAM by default. To prevent possible loss of configuration, this boot configuration must be backed up. One of the backup copies of the configuration can be stored on a TFTP server. The copy running-config tftp command can be used for this. The steps in this process are listed below:
-Enter the copy running-config tftp command.
-When prompted, enter the IP address of the TFTP server to store the configuration file.
-Enter the name you want to give the configuration file or accept the default name.
-Confirm the choices by typing yes each time.
The router configuration can be restored by loading the configuration backup file from a TFTP server. The following steps describe this process:
1-Enter the copy tftp running-config command.
2- When prompted, select a host or network configuration file.
3-At the system prompt, type the IP address of the TFTP server where the configuration file is located.
4- At the system prompt, enter the name of the configuration file or accept the default name.
Confirm the configuration file name and server address provided by the system .
6-Errors identified at layer 1 can be as follows:
Broken cables
Disconnected cables
Cables connected to inappropriate ports
Unstable connections
Cables inappropriate for the task at hand (console cables, crossover cables and straight cables must be used wisely)
Transceiver problems
DCE wiring problems
DTE wiring problems
Units off
7-Errors identified at layer 2 can include the following:
Misconfigured serial interfaces
Incorrectly configured Ethernet interfaces
Inappropriate encapsulation assembly (HDLC is used by default for serial interfaces)
Clock Frequency problem
Network adapter issues
8-Errors identified at layer 3 level may include:
Routing protocol not enabled
Invalid routing protocol enabled
Incorrect IP addresses
Incorrect subnet masks
9- Reset password
This procedure has the advantage of not overwriting the configuration, simply changing the passwords while keeping the existing configuration. The connection must be made by a console cable.
You must then restart the router with the switch and press the CTRL key and "Pause" or "Break" on the keyboard within 30 seconds after booting. The following screen should then appear:
After rebooting the router asks if you want to enter the SETUP mode, answer "no" to this question.
The next step is to enter the privileged mode with this "blank" configuration.
No password configuration is blank
Cisco EEM Essentials:
Embedded Event Manager or Cisco EEM is a software component of Cisco IOS that allows network engineers to automate networking tasks, respond to certain types of events, and improve the intelligence of Cisco networking devices. EEM detects real-time network event reporting and tracking. It automates different tasks by using applets and scripts. EEM is embedded in the Cisco IOS, so there will be no need for an external controller or monitoring tool.
pplets and scripts are used in Cisco EEM. Applets is a series of commands within a CLI. It is created using the “event manager applet”. Applets are designed to respond to a certain type of traffic, such as syslog messages, and SNMP traps. Applets are created in this way.
Tcl is an ideal language to use for automated hardware and software testing, and it ma
well be the dominant language used for this purpose. With Tcl you can easily connect to
testing hardware or internal APIs of an application, invoke test functions, check the
results, and report errors. Tcl's interpreted implementation allows tests to be created
rapidly, and the tests can be saved as Tcl script files to reuse for regression testing.
If you are testing a software application, Tcl allows you to connect directly to lower-level
APIs within the application, which provides much more precise and complete testing.
Auto_Rcovery of FastEthernet0/0 Via Cisco EEM
I am going to write an applet for automatic interface recovery. When the interface fastethernet0/0 of a router goes down, then it should recover automatically. The network administrator should recover it manually, but it should be recovered through the EEM apple
Auto-Recovery Interface is our applet name. In the 2nd line when a pattern matches with the Syslog message “. *FastEthernet0/0.down. *”, then it will configure the interface with auto as shown in the above screenshot.
Suppose we want to shut down the interface fast Ethernet 0/0 of a router R1. Then, see the result of a Router in the below screenshot:
Saving configuration to NVRAM
If a network administrator wants to save the running configuration after every hour, then he can simply follow the following Cisco EEM script to automate it.
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