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Cisco-Linksys SRW 248G4 - system firmware recovery



In this article I will describe how to proceed if your firmware upgrade on SRW 248G4 switch failed and the switch then stop working.

I have found only one solution how to recover from this disaster and it is sending a new firmware over PC serial (COM) port using xmodem protocol. A new firmware can be send to the failed switch with the help of Startup menu of the switch. The Startup menu can be entered when the switch is booting.

So, steps are following:

  1. Prepare correct switch firmware.
  2. Prepare communication software (terminal) which support Xmodem protocol. Windows OSs up to Vista has the HyperTerminal SW. In Vista or Win 7 we need some another, SecureCRT for example? Connect PC using its serial COM line to the console port of the switch. Start terminal sw, do not forget setup correct line settings, which are different as Cisco devices has. Linksys has:
  • speed 38400, data bits 8, stop bits 1, no parity, no flow control

To enter the Startup menu of the switch do following

  1. Power off and then power on your switch.
  2. Watch for the auto-boot message.

Autoboot in 2 seconds - press RETURN or Esc. to abort and enter prom.

Preparing to decompress
..
..
97%
98%
99%
100%

 FAIL !!! Check image for valid file. 

Please download a new image.
  1. Select Send File from the Transfer pull-down menu. Choose the file from the disk, choose Xmodem as the protocol

 

than press Send button and the software will start sending the file

switch will write

Downloading code using XMODEM.

when the download will end the switch will inform us about that and perform reboot

 -- Download complete --


Calculating file's checksum...OK

Erasing FLASH ->>>>>>>>>>>>>>>>>>>>>>>>>>

Writing to flash 0x32d980 records...

Setting checksum: 0x19527ef1 , Address: 0x0

OK.

Flash programming success.


 Perform WARM BOOT ...

and if everything is OK we will see the login dialog: