Router configs

(config = configuration)

                       

The router config is a file that is stored in memory.  It is not the IOS (Internetwork Operating System).  The IOS is the operatinng system of the router, whereas the config is a set of text-based commands that define how the router operates.  There are two types of configurations:

 

startup config – this is the initial config that is stored in the NVRAM, and is refreshed when the router is rebooted

 

running config - the current configuration of the router, stored in DRAM.  You may have just changed several options and they would then become part of the running config

 

*** all the following commands for working with config files are done in priviledged mode, not in config mode.  This is counter-intuitive but true.  The config mode is actually only a temporary gateway mode to get to extended modes.  Very little can be done in the config mode.

 

*** oddly, to view or copy configs you must be in Priveledged mode – not config mode.  Config mode is used to change or create configs – priveledged mode is use to view or copy configs

 

to view the configs :

 

sh running-config           or         sh run

sh startup-config           or         sh start

 

Save the running Config to NVRAM :

 

Copy run start              - copies the “run start” config (the startup config) to NVRAM

-         this is short for “copy running-config startup-config”

CAUTION:  do not type “copy start run” – it will blow away all your hard work that you did to configure the router !!!  This is a common error.

 

Erase the Startup Config

 

write erase                    - older command - does the same thing as erase startup-config

erase start                     - short for “erase startup-config”, removes the config from NVRAM
NOTE: the only need for this would be a corrupt startup-config

 

Reset or Reload the router 

 

I           (2500 series)

 

reset     (2600 series)

 

reload   (unsure about this) - erases the startup config, and reload the router, you will get an error upon “show startup-config”, until you “copy run start”

 

 

Copying Config files between RAM, NVRAM and TFTP

 

NOTE – merge vs replace:  Copy to run (DRAM, the running-config file) merges the text files (copy start run or copy tftp run would do this) – it appends the copied file to the end of the commands already in the run file.  Copy to NVRAM or TFTP does a normal copy where the file is replaced  (such as copy run start). 

 

The most common method of setting up a large network and keeping numerous config files available for copying, is to store them on a TFTP (Trivial FTP) server.

 

The syntax is:                copy  from   to

Example:  copy start run            - copies (appends) startup config (NVRAM) to running config (DRAM)

 

Example:  copy tftp start run                  - copies (appends) the tftp starup file to the DRAM running config info