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(which represents 0010 and 1111 in binary), the router looks for boot system commands in
startup-configuration to tell it where to find IOS. If there are no boot system commands in the
startup-configuration, the router then searches in the default places, then flash, then ROM, and then a
tftp server.
"
0x00: If the configuration-register value ends in 0x00 (binary 0000), the router enters Rom Monitor
Mode. (See Chapter 8.)
"
0x01: If the configuration register value ends in 0x01, the router boots from ROM.
Changing your boots
If you wish to change the source location from which you want the router to load the IOS system files, you
can use the command boot system along with the parameter that directs the router to the source you wish to
use. It is this command that the router will look for if the configuration-register tells it to look in the
startup-configuration for boot system commands.
The following help command display shows the various parameters that can be used to tell the router where
to look for the IOS.
CCNA_For_Dummies(config)#boot system ?
WORD System image filename
flash Boot from flash memory
mop Boot from a Decnet MOP server
rcp Boot from a server via rcp
rom Boot from rom
tftp Boot from a tftp server
Instant Answer The current setting of the configuration-register is displayed using the Show Version
command.
ItÇs not a trivial matter
Remember Configuration files can also be stored outside the router itself. Using the Trivial File Transfer
Protocol (TFTP), configuration files can be copied and stored on a TFTP server. In fact, after theyÇre backed
up to the TFTP server, these files can be used as the source of the configuration during the boot sequence.
However, the primary reason to back up the configuration to an outside server is to ensure that the router has a
source of its configuration if the configuration file on the router gets corrupted or accidentally (or possibly,
intentionally) erased.
Backing up the flash
ItÇs a good idea to have a backup copy of the routerÇs flash memory on a TFTP server just in case the
configuration file on the router gets corrupted or erased. HereÇs a sample of the command used and the results
displayed by the router:
CCNA_For_Dummies(boot)#copy flash tftp
PCMCIA flash directory:
File Length Name/status
1 3070408 c1600-y-l.111-12.AA
[3070472 bytes used, 1123832 available, 4194304 total]
Address or name of remote host [255.255.255.255]? 192.168.1.2
Source file name? c1600-y-l.111-12.AA
Destination file name [c1600-y-l.111-12.AA]?
Verifying checksum for Øc1600-y-l.111-12.AAÇ (file # 1)... OK
Copy Øc1600-y-l.111-12.AAÇ from Flash to server
as Øc1600-y-l.111-12.AAÇ? [yes/no]yes
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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Upload to server done
Flash device copy took 00:00:52 [hh:mm:ss]
Remember You can upgrade flash memory using the TFTP server. After you obtain an upgraded IOS image
from Cisco, store it on the TFTP server and use the copy TFTP flash command to move it to the routerÇs flash
memory.
Now that itÇs started, back it up!
The two types of configuration files stored on a router are the startup configuration file and the running
configuration file. These files can be copied to and from each other as well as to and from the TFTP server.
The commands to copy these files are shown in the following list. (Remember: To use these commands, you
must be in Enable Privileged mode the one with the # character prompt.)
Remember
CCNA_For_Dummies#copy start tftp
CCNA_For_Dummies#copy run tftp
CCNA_For_Dummies#copy tftp run
CCNA_For_Dummies#copy tftp start
These examples copy the startup configuration to the TFTP server; copy the running configuration to the
TFTP server; copy the configuration stored on the TFTP server to the running configuration file on the router;
and copy the configuration stored on the TFTP server to the startup configuration file on the router,
respectively. Using the command completion help built into the command line interface, itÇs perfectly
acceptable to type in only the word start or run to indicate the startup and the running configuration.
Instant Answer The other copy command that you may see on the exam is
CCNA_For_Dummies#copy run start
This command is used to save the running-configuration to flash.
Making copies...
HereÇs an example of the console output that results from the command to copy the startup configuration to a
TFTP server:
CCNA_For_Dummies#copy star tftp
Remote host []? 192.168.1.5
Name of configuration file to write [ccna_for_dummies-confg]?
Write file ccna_for_dummies-confg on host 192.168.1.5? [confirm]
Writing ccna_for_dummies-confg !! [OK]
Instant Answer Remember that you must be in Exec Enable (Privileged) mode to copy configuration files.
Covering your tracks
Remember ItÇs a very good idea that after you update the running configuration that you make sure the
startup configuration is also updated. Probably the best way to do this is to simply copy the running
configuration to the startup configuration. The command to accomplish this is:
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 CNA_For_Dummies#copy run star
Building configuration...
If you forget to update the startup configuration, or decide not to, the next time you boot the router it will
revert to its previous configuration, which could be actually what you planned all along.
A command performance
Time-Saver Table 10-1 includes a list of commands that not only should you know, but you should also
know when to use them and why.
Table 10-1: Configuration Startup and Save Commands
Command Action When to Use [ Pobierz całość w formacie PDF ]