You want to clear an old configuration out of your router and return it to a factory default configuration.
You can delete the current startup configuration files and return the router to its factory default settings with the erase nvram: command:
Router1#erase nvram:
Erasing the nvram filesystem will remove all files! Continue? [confirm] <enter>
[OK]
Erase of nvram: complete
Router1#reload
System configuration has been modified. Save? [yes/no]: no
Proceed with reload? [confirm] <enter>
You can achieve the same result with the erase startup-config command:
Router1#erase startup-config
Erasing the nvram filesystem will remove all files! Continue? [confirm] <enter>
[OK]
Erase of nvram: complete
Router1#reload
Proceed with reload? [confirm] <enter>
Before you redeploy an old router that you have previously used for another purpose, it is a good idea to completely erase the old configuration. This ensures that the router starts with a clean configuration. However, if you did this on a production router, it would wipe out the configuration and disable all of the interfaces. Fortunately, completely deleting your configuration requires two steps: you must erase the startup configuration, then reload the router.
After you erase your startup configuration file and reload, the router will enter its configuration dialog mode. Most experienced Cisco engineers prefer to skip this mode:
--- System Configuration Dialog ---
Would you like to enter the initial configuration dialog? [yes/no]: no
Would you like to terminate autoinstall? [yes]: yes
Press RETURN to get started
!
Router>
At this point, the router's configuration has been returned to the factory defaults:
Router#show running-config Building configuration...
Current configuration : 431 bytes
!
version 12.2 service timestamps debug uptime service timestamps log uptime no service password-encryption !
hostname EBRAHMA
!
ip subnet-zero
!
interface Ethernet0
no ip address shutdown
!
interface Ethernet1
no ip address shutdown
!
interface Serial0
no ip address shutdown
!
interface Serial1
no ip address shutdown
!
ip classless
ip http server
ip pim bidir-enable
!
line con 0
line aux 0
line vty 0 4
!
end
EBRAHMA#
You can now safely reconfigure the router for its new function. Note that the factory defaults vary, depending on the level of IOS you are running and the hardware installed in the router.
If you accidentally erase the startup configuration file, you can still recover it if the router has not yet been reloaded. Simply copy the running configuration back to the startup configuration:
EBRAHMA1#show startup-config
startup-config is not present
EBRAHMA1#copy running-config startup-config
Building configuration...
[OK]
EBRAHMA1#show startup-config
version 12.2
service timestamps debug datetime msec
service timestamps log datetime localtime
service password-encryption
service password-encryption
!
hostname EBRAHMA1
<removed for brevity>
If the router's configuration is erased and the router is reloaded, it will either need to be reconfigured manually from memory.
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