Last weekend, one of my 3com 4250T switches stopped functioning. I used a multimeter and the fuse seems okay, but it's dead as a doorknob. Since my switches are stacked to one virtual unit, I bought a second hand 4250T to replace the broken one.
As often with second hand crap, this switch contained settings from the last location. Including an unknown password.
Fortunately, the switches have a recovery mode (which can also be disabled, so below instructions may not work on another switch).
I connected the switch to a RS232 port using a null-modem cable. If you know the switches IP, you can also use telnet.
*** Password Recovery Mode ***
The administrative password will be cleared if a hard reset operation is
carried out on the device within 30 seconds.
If a hard reset operation is not carried out during this period, the device
will return to the CLI login prompt
countdown = 30...29...28...
Pull the plug of the switch before the countdown reaches 0. When you boot it again, you can login using the default user "admin" and simply press enter for 'password'.
This manual may work on:
3COM SuperStack 3 4400
3COM SuperStack 3 4900
3COM SuperStack 3 4924
3COM SuperStack 3 4950
3COM SuperStack 3 4300
3COM SuperStack 3 Webcache
3COM SuperStack 3 Webcache 1000
3COM SuperStack 3 Webcache 3000
3COM SuperStack 4200 series
3COM SuperStack 3 Switch 4250T
3COM SuperStack 3 Switch 4226T
3COM Switch 4050
3COM Switch 4060