Cisco USB Console Cable on Mac OSX

0 Posted by - May 27, 2014 - tech

I recently had to dust off an old Cisco switch to setup a lab here in my home office.  I had no clue what the enable password was so I needed to hard reset the box to get in.  Being all in on cloud, I have forgotten more hardware knowledge than I’d care to admit to.    I no longer have any Windows based machines in the house with serial ports, so here’s a what I gathered to reset the switch using my Macbook Pro:

  1. USB to RJ-45 Serial Cable (here or search eBay for “Cisco USB RJ45 FTDI”.
  2. USB Serial driver for OSX (Virtual Com Port driver)
  3. The relevant Cisco password recovery page.

After installing the FTDI USB serial driver, I read the man page on “cu” to get the options right.  The last time I used something similar was “tip” on my NeXTstation (yeah I’m old and still have it).   So anyway, after finding the correct tty device, here we go:

# cu -l /dev/tty.usbserial-A501VIU9 -s 9600 --parity=none --nostop
ROMMON: Cold Reset frame @0x00000000
ROMMON: Reading reset reason register
ROMMON: Valid NVRAM config

System Bootstrap, Version 12.0(7)W5(15a) RELEASE SOFTWARE 
Copyright (c) 2000 by cisco Systems, Inc.

ROMMON: Initializing exceptions
ROMMON: Initializing TLB 
ROMMON: Initializing cache 
ROMMON: Sizing and zeroing main memory ... 64 MBytes
ROMMON: Sizing non-volatile memory ... 128 KBytes

cat2948g platform with 65536 Kbytes of main memory
[ ... ]

You may need to reset/power cycle the switch to see activity on the tty device.

The password recovery instructions say to send a “break” to the switch upon power cycle (within the first 60 secs).  To do this with “cu”, you’ll need to use the cu escape command to send a break.  This is ~# by default.   Once sent, you should see something like:

monitor: command "boot" aborted due to user interrupt
rommon 1 > 
rommon 1 >

You should be golden with the directions at the point.



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