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Configuration Processes and the Configuration File 39
Managing Configuration Files
The CCNA exam requires that you be able to distinguish between the configuration file used at
startup and the active configuration file. The startup configuration file is in NVRAM; the other
file, which is in RAM, is the one the router uses during operation. The router copies the stored
configuration file from NVRAM into RAM as part of the boot process. Exterior to the router,
configuration files can be stored as ASCII text files anywhere using TFTP.
Cisco provides several methods of manipulating configuration files. CiscoWorks and other
management products let you create configurations for one or many routers without logging on
to those routers. NetSys Connectivity Tools actually check all the configuration files in your
network, make suggestions for improvements, and uncover errors. The most basic method for
manipulating configuration files and moving them into and out of a router, however, is by using
a TFTP server. The copy command is used to move configuration files among RAM, NVRAM,
and a TFTP server. The files can be copied between any pair, as Figure 2-8 illustrates.
Figure 2-8
Locations for Copying and Results from Copy Operations
The commands can be summarized as follows:
copy {tftp
|
running-config
|
startup-config} {tftp
|
running-config
|
startup-config}
The first parameter is the "from" location; the next one is the "to" location. (Of course, choosing
the same option for both parameters is not allowed.)
Confusion about what these commands actually do is pervasive. Any copy command option
moving a file into NVRAM or a TFTP server replaces the existing file. Any copy command
option moving the file into RAM, however, is effectively an add or merge operation. For
example, only one host name Siberia configuration command is allowed. Therefore, a config
file copied into RAM with hostname Siberia in it replaces the previous hostname command
(if any). However, if the file being copied has the access-list 1 permit host 1.1.1.1 command
in it, and if an access list number 1 already exists in the RAM configuration file, then access-
list 1 permit host 1.1.1.1
is placed at the end of that existing access list (access lists are
comprised of a list of configuration commands referencing the same list number or name). The
RAM
TFTP
NVRAM
Merge
Merge
Replace
Replace
Replace
Replace
ch02.fm Page 39 Monday, March 20, 2000 4:57 PM