Configuration register
It is a hexadecimal value that specifies the router from where to load the IOS.
0x2100
=> This value specifies the router to load the IOS form the flash into the RAM.
=> It will break the booting sequence of the router.
=> Router will go into the rommon (ROM MONITOR) mode.
=> This mode is used to troubleshooting, maintenance and repair of the router
=> The commands used in this mode are different from the router normal mode.
=> rommon > is appear when we enter into the rommon mode.
=> To enter into rommon mode we can use the key combination as ctrl + break.
0x2101
=> This value specifies the router to not load the IOS from flash to RAM.
=> This value specify the router to boot from mini IOS which is present in the ROM.
=> The command prompt is as router>
0x2102
=> This is the default value for each router
=> This value specifies the router to load IOS from the flash to RAM and then load the startup configuration (saved configuration) from the NVRAM.
=> The command prompt in this mode is router>
0x2142
=> This value specifies the router to load the IOS from flash to RAM.
=> This value specifies the router to bypass the startup configuration.
=> This mode is used to password breakup while saving the configuration.
=> This mode is used to break the password.
=> When we start the router in this mode it bypass the startup configuration and then it will ask you
i) Would you like to enter into initial configuration dialog? yes/no. n
ii) After pressing N you will enter into the CLI (Command Line Interface)
=> Now you are able to configure the new value to your router.
Password recovery
1. Power on the router and press CTRL + BREAK key combination till the router will go into the rommon mode.
2. Change the configuration register value from 0x2102 to 0x2142
The command is confreg 0x2142
3. restart the router
The command to reset the router is reset
4. use the copy start run
a. by using the above command copy start run we try to make the start configuration to running configuration so that other configuration remain same while breaking the password. If we does not use this step even then we are capable to break or change the password but it can’t save the startup configuration.
5. Change all the required passwords.
6. Change the configuration register value back to 0x2102 from the 0x2142.
a. To do so we use the command as
i.Config-register 0x2102
7. Make all the changes permanently saved using the command
a. Copy run start (or)
b. Write
Backup and restore
1. First of all, on the computer where you want to take backup must have a software as Cisco TFTP server.
2.Check the physical connectivity among the computer and router.
a. To connect the router and computer cross wire is required
b. We can connect the pc to switch and switch to router if we have only straight wire.
c. Assign the IP address to both computer and router.
d. IP address of the router is assigned as the default gateway to computer
3. Complete the IP address related formalities over both computer as well as router.
4. Test the physical connectivity using the ping command from computer to router and router to computer.
5. Install the Cisco TFTP server software over the computer and start it while taking the backup or restore the IOS. It must be open.
6. backup of router IOS
a. Use show flash to see the name of router IOS. And copy that name.
b. Then use the command copy flash TFTP to take the back up of router IOS.
7. Backup of the router startup configuration.
a.Use command copy start TFTP.
8. Backup of the router running configuration
a. Use command copy run TFTP
RESTORING
9. Restore the router IOS
a. Use command copy TFTP flash
10. Restore the router running configuration
a. Use command copy TFTP run
11.restore the router startup configuration
a. use command copy TFTP start
It is a hexadecimal value that specifies the router from where to load the IOS.
0x2100
=> This value specifies the router to load the IOS form the flash into the RAM.
=> It will break the booting sequence of the router.
=> Router will go into the rommon (ROM MONITOR) mode.
=> This mode is used to troubleshooting, maintenance and repair of the router
=> The commands used in this mode are different from the router normal mode.
=> rommon > is appear when we enter into the rommon mode.
=> To enter into rommon mode we can use the key combination as ctrl + break.
0x2101
=> This value specifies the router to not load the IOS from flash to RAM.
=> This value specify the router to boot from mini IOS which is present in the ROM.
=> The command prompt is as router>
0x2102
=> This is the default value for each router
=> This value specifies the router to load IOS from the flash to RAM and then load the startup configuration (saved configuration) from the NVRAM.
=> The command prompt in this mode is router>
0x2142
=> This value specifies the router to load the IOS from flash to RAM.
=> This value specifies the router to bypass the startup configuration.
=> This mode is used to password breakup while saving the configuration.
=> This mode is used to break the password.
=> When we start the router in this mode it bypass the startup configuration and then it will ask you
i) Would you like to enter into initial configuration dialog? yes/no. n
ii) After pressing N you will enter into the CLI (Command Line Interface)
=> Now you are able to configure the new value to your router.
Password recovery
1. Power on the router and press CTRL + BREAK key combination till the router will go into the rommon mode.
2. Change the configuration register value from 0x2102 to 0x2142
The command is confreg 0x2142
3. restart the router
The command to reset the router is reset
4. use the copy start run
a. by using the above command copy start run we try to make the start configuration to running configuration so that other configuration remain same while breaking the password. If we does not use this step even then we are capable to break or change the password but it can’t save the startup configuration.
5. Change all the required passwords.
6. Change the configuration register value back to 0x2102 from the 0x2142.
a. To do so we use the command as
i.Config-register 0x2102
7. Make all the changes permanently saved using the command
a. Copy run start (or)
b. Write
Backup and restore
1. First of all, on the computer where you want to take backup must have a software as Cisco TFTP server.
2.Check the physical connectivity among the computer and router.
a. To connect the router and computer cross wire is required
b. We can connect the pc to switch and switch to router if we have only straight wire.
c. Assign the IP address to both computer and router.
d. IP address of the router is assigned as the default gateway to computer
3. Complete the IP address related formalities over both computer as well as router.
4. Test the physical connectivity using the ping command from computer to router and router to computer.
5. Install the Cisco TFTP server software over the computer and start it while taking the backup or restore the IOS. It must be open.
6. backup of router IOS
a. Use show flash to see the name of router IOS. And copy that name.
b. Then use the command copy flash TFTP to take the back up of router IOS.
7. Backup of the router startup configuration.
a.Use command copy start TFTP.
8. Backup of the router running configuration
a. Use command copy run TFTP
RESTORING
9. Restore the router IOS
a. Use command copy TFTP flash
10. Restore the router running configuration
a. Use command copy TFTP run
11.restore the router startup configuration
a. use command copy TFTP start
For more information about this lab please visit our below link.
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