Cisco 3750G stuck in loop at login

[NormMuelleman]

I am experiencing an issue with a Cisco Catalyst 3750 switch. The switch was on the network operating normally. I replaced the switch with another, and took this one back to our office. I attempted to log into the device via console port. This is done everyday on a support laptop; the settings are correct for the connection application (TeraTerm). I connected to several other devices today with no issues.

However, on this particular device (which has probably seen better days), I can watch the boot-up process occur. The login banner displays, hangs for a moment, then gives me the familiar "hit return to get started". However, I hit return, and nothing happens; it loops back to the login banner, and repeats. Even if I don't hit return, it will loop back to the login banner.

I've checked the connections, the cable, and have rebooted both the support laptop and the device itself. I've logged into different devices just fine. Is there some way to break the loop so I can ultimately login local and wipe the device?

[Peter Paluch · Accepted solution]

Hello Norm,

I suggest you simply try performing the password recovery procedure to boot into a clean configuration. Something in the stored config probably does not work well with the current state of the switch - perhaps the authentication was performed towards a RADIUS or TACACS server, and now that server is not available, resulting in that looping you see.

Proceed as follows:

1. Disconnect the switch from mains.
2. Press the MODE button at the front panel, and while holding it pressed, connect the switch back to power.
3. Hold the MODE for several seconds until the Power LED on the front panel either changes color, or starts blinking in a different pattern. Usually, about 10 seconds of continuous depression of the MODE are necessary.
4. After releasing the MODE button, the switch should provide you with a bootloader prompt. Enter the following commands (do not use any TAB completion nor arrows for line editing - they are not supported and will render the currently-entered command unrecognizable by the switch):
   flash_init
   load_helper ! This command may not be recognized - if so, ignore it
   rename flash:config.text flash:config.old
   boot
5. This sequence of commands will rename your current configuration file to the config.old file - you will be able to find it in the FLASH afterwards. The switch should now boot into a clean configuration.

Let me know if this worked for you.

Best regards,

Peter

[NormMuelleman]

I was thinking about trying password recovery and see if that got it out of the loop. At least I was in the right direction

This stopped the loop, and I was able to delete and wipe and have the device baselined, ready to go again Thanks much!