Backing up and Restoring IOS
----------------------------
Basic parts:
Flash
- stores IOS (around 29 MB)
- slow
- is copied to RAM when device boots
RAM
- holds running config and IOS
- fast but volatile
NVRAM
- available on some devices to hold running
config
- fast and non-volatile
Where to put back
ups?
HTTP - web server
FTP - old way; requires username and password
TFTP - uses UDP; don't require username and
password
Configuration Registers
-----------------------
Determines how device
boots up
|
2100 (rommon)
|
device will boot
here if it can't detect an IOS
|
|
2101 (rxboot)
|
limited version of
IOS
|
|
2012
|
normal boot
|
|
2142
|
ignore/bypass NVRAM
|
How Cisco devices boot
----------------------
1. checks config
register
2. checks for `boot
system` command in startup config
3. looks for first
IOS image in flash
4. broadcast for a
tftp server
Commands
--------
|
key command
|
copy ?
|
|
general syntax of
`copy`
|
copy FROM TO
|
|
copies flash to
TFTP server
|
copy flash:
|
|
same as above but
uses prompt
|
copy flash tftp
|
|
prints flash
information
|
show flash
|
|
restoring
|
copy TFTP flash
|
|
copies running
config
|
copy running-config
DESTINATION
|
|
displays
configuration register
|
show version
|
Some notes:
- don't restore running config because it
will just merge it to the present
- e.g: copy tftp running-config
- proper way is to restore running config
from offsite box to startup config
- e.g: copy tftp start-up config
Tutorials
---------
|
recovering enable
password
|
1. Boot into rommon
-> connect to device via console
-> power off device via physical switch
-> power on device
-> hit CTRL+BREAK
2. Change config
register to bypass NVRAM
rommon 1 >
confreg 0x2142
rommon 2 > reset
3. Copy the startup
config to the running config and change
enable password
Router> enable
Router# copy
startup-config running-config
Router# conf t
Router(conf)#
enable secret newpassword
Router(conf)# exit
Router# copy run
start
|
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