hardMultiple Choice
300-410 Practice Question: Is troubleshooting a router that has been running…
A network engineer is troubleshooting a router that has been running for 200 days. The router experiences a sudden reboot, and after reload, the configuration is missing. 'show startup-config' returns 'startup-config is not present'. The engineer checks the boot variable: 'boot system flash:ios-image.bin'. What is the most likely cause of the configuration loss?
⚠ Common exam trap
Cisco often tests the distinction between a missing startup configuration (due to failure to save) and a configuration that is present but ignored (due to the configuration register), so candidates must recognize that 'startup-config is not present' indicates an empty NVRAM, not a register override.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The engineer did not execute 'copy running-config startup-config' before the reboot.
The router's startup configuration is stored in NVRAM, and if the engineer never executed 'copy running-config startup-config' (or equivalent 'write memory'), the running configuration exists only in RAM. Upon reboot, the router loads the IOS image from flash as specified by the 'boot system flash:ios-image.bin' variable, but NVRAM contains no saved startup configuration, resulting in 'startup-config is not present'. This is a classic operational oversight where changes are made to the running configuration but not saved to NVRAM.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The router's NVRAM has a hardware failure and lost the configuration.
Why it's wrong here
While NVRAM can fail, a hardware failure would typically manifest during boot as a checksum error, an inability to access the configuration, or a router that cannot properly start. In this scenario, the router rebooted cleanly and reported that startup-config is 'not present', which more directly points to an empty NVRAM because the running configuration was never saved. NVRAM failures are rare and usually accompanied by other symptoms, making this explanation far less plausible than a simple administrative oversight.
- ✓
The engineer did not execute 'copy running-config startup-config' before the reboot.
Why this is correct
The running-config is stored in volatile RAM and is lost on reload, while the startup-config resides in NVRAM. If the engineer never executed 'copy running-config startup-config' (or 'write memory') during the 200 days of uptime, the startup-config file would remain empty or nonexistent. After reboot, the router loads with no saved configuration, causing 'show startup-config' to report that the file is not present, exactly as shown.
- ✗
The 'boot system' command points to a TFTP server that also contains a configuration file, overwriting the local startup-config.
Why it's wrong here
The 'boot system' command only tells the router which IOS image or boot location to use, such as flash or a TFTP server; it does not manage configuration files. Overwriting the local startup-config would require the 'boot config' command, and even then the local NVRAM file would not be erased or replaced automatically. Therefore, a TFTP server with a configuration file cannot remove the local startup-config simply because 'boot system' points to that server.
- ✗
The router's configuration register is set to 0x2142, ignoring startup-config.
Why it's wrong here
Setting the configuration register to 0x2142 makes the router bypass startup-config during boot by ignoring NVRAM, but it does not delete or overwrite that configuration. The startup-config remains intact in NVRAM, so 'show startup-config' would still display the saved configuration rather than returning 'not present'. A 0x2142 register explains missing running-config after reload, but not a missing startup-config file.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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