Troubleshooting Win: The Mystery of the “Disappearing Config” on a Core Switch
Today, I solved an issue that had been giving us headaches for a long time. Every time there was a power failure, our core switch would completely forget its startup configuration.
Even after several attempts (including by my boss), the switch kept booting as if it had no memory of its saved settings. The culprit? A misconfigured configuration register.
Here’s what I discovered:
The switch was set to 0x142, which tells the device to ignore the startup-config at the next reload. No wonder it kept resetting itself.
The Fix (for anyone who might face this in the future):
1. conf t – enter global config mode
2. no system ignore startupconfig switch all – stop ignoring the startup-config
3. config-register 0x102 – set the register to load startup-config on boot
4. do wr – save the config
5. reload – reboot the switch with correct settings
After this, the switch now boots with its saved configuration every single time.
Lesson: Sometimes, it’s not about replacing hardware or blaming power issues, it’s about knowing what a single hexadecimal value can do in your config.
#Networking #Cisco #CiscoSwitch #Switch #ITSupport #Troubleshooting #Persistence
