The router can bypass the startup configuration stored in non-volatile RAM (NVRAM) during its boot sequence. In order to check whether this problem occurs, complete these steps:
- After your router boots up, do not enter the initial configuration dialog (choose No when prompted).
-– System Configuration Dialog —Would you like to enter the initial configuration dialog? [yes/no]: no
Press Enter to get to the
Router>prompt.Type enable , and press ENTER to enter the privileged mode.
From the
Router#prompt, typeshow start and press ENTER. Your configuration must be the one that was saved before reboot or power loss. If you find that the configuration is not the same, it is possible that the router has ignored the startup configuration. Proceed to Step 5.Type show version , press ENTER, and look at the last line in the output that appears. Here is an example:
Router#show version Cisco Internetwork Operating System Software IOS (tm) 2500 Software (C2500-JS-L), Version 12.1(5), RELEASE SOFTWARE (fc1)Copyright (c) 1986-2000 by cisco Systems, Inc.Compiled Wed 25-Oct-00 05:18 by cmongImage text-base: 0x03071DB0, data-base: 0x00001000ROM: System Bootstrap, Version 5.2(8a), RELEASE SOFTWAREBOOTFLASH: 3000 Bootstrap Software (IGS-RXBOOT), Version 10.2(8a), RELEASE SOFTWARE (fc1)Router uptime is 7 minutesSystem returned to ROM by reloadSystem image file is “flash:c2500-js-l_121-5.bin"cisco 2500 (68030) processor (revision D) with 16384K/2048K bytes of memory.Processor board ID 03867477, with hardware revision 00000000Bridging software.X.25 software, Version 3.0.0.SuperLAT software (copyright 1990 by Meridian Technology Corp).TN3270 Emulation software.1 Token Ring/IEEE 802.5 interface(s)2 Serial network interface(s)32K bytes of non-volatile configuration memory.16384K bytes of processor board System flash (Read ONLY)Configuration register is 0x2142
In this example, the configuration register shows 0x2142. The router bypasses the startup configuration stored in NVRAM during its boot sequence. This feature is normally used during a password recovery procedure.
| This table explains the configuration register bit meanings: Bit No. | Hex | Meaning |
|---|---|---|
| 00-03 | 0x0000-0x000F | Boot Field Parameters 0x0000 Stays at the system bootstrap prompt 0x0001 Boots system image on EPROM 0x0002-0x000F Specifies a default netboot filename. |
| 06 | 0x0040 | Ignore NVRAM contents. |
| 07 | 0x0080 | OEM bit enabled to exclude details in boot messages. |
| 08 | 0x0100 | Break disabled. |
| 10 | 0x0400 | IP broadcast with all zeros. |
| 11-12 | 0x0800-0x1000 | Console line speed. |
| 13 | 0x2000 | Boot default ROM software if network boot fails. |
| 14 | 0x4000 | IP broadcasts do not have net numbers. |
| 15 | 0x8000 | Enable diagnostic messages and ignore NVRAM contents. |
The factory-default setting for the configuration register is 0x2102. This indicates that the router should attempt to load a Cisco IOS® software image from Flash memory and load the startup configuration.
configure terminal , and press ENTER.
Type config-register 0x2102, and press ENTER.
Type end , and press ENTER.
To verify the configuration register change, type show version at the Router# prompt, and review your show version command output again. Look for the configuration register setting, which must show a new value upon the next reload. Here is an example:
Router#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)#config-register 0x2102 Router(config)#end Router#show version Cisco Internetwork Operating System Software IOS (tm) 2500 Software (C2500-JS-L), Version 12.1(5), RELEASE SOFTWARE (fc1)Copyright (c) 1986-2000 by cisco Systems, Inc.Compiled Wed 25-Oct-00 05:18 by cmongImage text-base: 0x03071DB0, data-base: 0x00001000ROM: System Bootstrap, Version 5.2(8a), RELEASE SOFTWAREBOOTFLASH: 3000 Bootstrap Software (IGS-RXBOOT), Version 10.2(8a), RELEASE SOFTWARE (fc1)Router uptime is 11 minutesSystem returned to ROM by reloadSystem image file is “flash:c2500-js-l_121-5.bin"cisco 2500 (68030) processor (revision D) with 16384K/2048K bytes of memory.Processor board ID 03867477, with hardware revision 00000000Bridging software.X.25 software, Version 3.0.0.SuperLAT software (copyright 1990 by Meridian Technology Corp).TN3270 Emulation software.1 Token Ring/IEEE 802.5 interface(s)2 Serial network interface(s)32K bytes of non-volatile configuration memory.16384K bytes of processor board System flash (Read ONLY)Configuration register is 0x2142 (will be 0x2102 at next reload)
When the router is reloaded, the new configuration register setting becomes active.
Router#reload System configuration has been modified. Save? [yes/no]: n Proceed with reload? [confirm]
Your router now loads with the startup configuration, and the configuration register is set to 0x2102. Your configuration loads properly after the next reload or power cycle.