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Why lose a router settings after a power outage?

Question:
After a power outage Cisco 1900 lost my router configuration, was saved, reload the configuration, save, reboot and no problem.
How to know if my router is properly, all my services run smoothly? Why it happens that configuration is lost?
Are there any benefits the settings saved in flash?
Answer:
Did you check if the NVRAM was empty or running config was empty?
If router booted with empty running config, it could be that startup got erased (NVRAM issue) or that it did not load it from startup to running (likely config-reg) issue.
Since in your case config-register ix 0x2102 and was not changed, the problem should be with NVRAM.
From me exprience, I have seen that in the following cases:
- config was not saved to NVRAM;
- at the time of powerdown the NVRAM startup file was accessed for editing (e.g. saving running config) and got corrupted or erased;
- NVRAM HW issues cause file system problems.
Is it reproducible in your case? E.g. if you powercycle the switch, do you see the same problem with config loss? If yes, check the NVRAM content. Cisco 1900 router That could give some hints.

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There are two main methods to return a Cisco router to its original factory defaults. These two methods are described below.
Method 1
1. uses the config-register 0x2102 command in global configuration mode.
2. Check the configuration register on the router by issuing the show version command.
3. The configuration register setting is displayed in the last line of the show version command output and should be set to 0x2102. If this is not the case, enter the config-register 0x2102 command once in global configuration mode.
router#configure terminal
router(config)#config-register 0x2102
router(config)#end
router#
4. If the show version command is issued again, the same line in the command output will have '(will be 0x2102 at next reload)' appended to the current register setting.
5. Erase the current start-up configuration on the router with the write erase command.
Reload the router with the reload command. When prompted to save the configuration, DO NOT save.
router#reload
System configuration has been modified. Save? [yes/no]: n
Proceed with reload? [confirm]
Once the router reloads, the System Configuration Dialog appears.
--- System Configuration Dialog ---
Would you like to enter the initial configuration dialog? [yes/no]:
The router is now reset to the original factory defaults.
Method 2
1. uses the config-register 0x2142 command in global configuration mode.
2. Enter the config-register 0x2142 command in global configuration mode.
router(config)#config-register 0x2142
This causes the router to ignore the start-up configuration on the next reload. If a show version is issued, the last line in the command output will have '(will be 0x2142 at next reload)' appended to the current configuration register setting.
3. Reload the router using the reload command in enable mode. It is not necessary to save when prompted to save the system configuration.
router#reload
System configuration has been modified. Save? [yes/no]: n
Proceed with reload? [confirm]
After the router has reloaded, the System Configuration Dialog appears.
4. Enter no to the question "Would you like to enter initial configuration dialog?"
5. Change the configuration register setting to 0x2102 by entering the config-register 0x2102 command once in global configuration mode.
6. Issue the write memory command in enable mode to overwrite the existing start-up configuration with the current running configuration.
7. Reload the router with the reload command in enable mode.
Once the router reloads, the System configuration Dialog appears.
--- System Configuration Dialog ---
Would you like to enter the initial configuration dialog? [yes/no]:
The router is now reset to the original factory defaults.
Note: The configurations below are stored in ROMMON, and cannot be reset to Factory Default Settings by the write erase or config-register 0x2142 commands.
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memory-size iomem <not default>

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how to reboot a cisco router?


From the privileged mode that is the # prompt type reload it will reload the router.

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