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1. After push Mode button on Catalyst 2950,3560 switch, plugin power
2. switch>flash_init
3. switch> load_helper
3. switch>dir flash:
4. switch>rename config.text config.old
5. switch> reset
After reboot your switch and then
6. switch>en
7. switch> conf t
8. switch#dir flash:
9. switch#rename config.old config.text
10. switch# erase startup-config
11. switch#reload
http://www.cisco.com/c/en/us/support/docs/switches/catalyst-2950-series-switches/41845-192.html