Network setup - How to - Routers - Cisco - Linux

How to save a configuration file larger than that NVRAM available in Cisco router

Sometimes it is possible that the configuration file (running-config) so that it grows larger than the available space in nvram. It is possible to compress the router configuration file before burning it to nvram and then to decompress when required.

Router1#configure terminal 
Enter configuration commands, one per line. End with CNTL/Z.
Router1(config)#service compress-config 
Router1(config)#end
Router1#

In most cases, Cisco routers equipped with enough NVRAM to save files of average size, however, some devices may configuration files grows so large that you can not save directly.

This could be a serious problem because at the time that the router is unable to save the settings in the NVRAM, it means that the router can not keep a copy of your configuration when restarted. It is not possible to know exactly which part of the configuration would be lost if it is restarted.

An alternative solution before going out to buy more memory NVRAM, would turn the compression option on the router with the command "service compress-config" from a terminal. Once this is necessary to file a copy of the NVRAM settings.

Router1#copy running-config startup-config 

Destination filename [startup-config]?
Building configuration... 
Compressed configuration from 9664 bytes to 4903 bytes[OK] 
Router1#

In this example we can see that the compression has reduced the configuration file to a little less than half the original size. In this case it was possible to save the file, however there will be cases in which compression is not yet sufficient to make the copy of the file so you need to check with how much NVRAM memory your router is equipped with the show version command and analyze option to buy more memory.

Router#show version 
Cisco IOS Software, 2800 Software (C2800NM-ADVIPSERVICESK9-M), Version 12.4(15)T1, RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2007 by Cisco Systems, Inc.
Compiled Wed 18-Jul-07 06:21 by pt_rel_team

ROM: System Bootstrap, Version 12.1(3r)T2, RELEASE SOFTWARE (fc1)
Copyright (c) 2000 by cisco Systems, Inc.

System returned to ROM by power-on
System image file is "c2800nm-advipservicesk9-mz.124-15.T1.bin"

cisco 2811 (MPC860) processor (revision 0x200) with 60416K/5120K bytes of memory
Processor board ID JAD05190MTZ (4292891495)
M860 processor: part number 0, mask 49
2 FastEthernet/IEEE 802.3 interface(s)
239K bytes of NVRAM.
62720K bytes of processor board System flash (Read/Write)
Configuration register is 0x2102

This router is equipped with a capacity of 239Kbytes of NVRAM. It is possible to identify the amount of NVRAM used by the show startup-config command as shown below.

Router1#show startup-config 
Using 463 bytes
!
version 12.4
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption