Cisco Small Business Switches. SF300, SG300 etc

 

Particularly the older ones, fail to update to the latest firmware (currently 1.4.11.5).

 

Complains of “illegal” file format or something similar.

 

Issue:

Can’t go from very old firmware to latest version in one step.

And that is very poorly documented  / hard to find on the Cisco.com site.

 

Fix part 1

• Update to version 1.3.5.58  first.
  300 series firmware link: https://software.cisco.com/download/home/284867260/type/282463181/release/1.3.5.58
• Use the relevant .ros file from inside the zip file. e.g. sx300_fw-13558.ros
• Set as active image
• reboot

If you try and then go to 1.4.11.5 now, it might work, depending on the exact model of switch, but you might also get a failure that complains about the file being “too large” / “too big”.

Fix part 2

• Update the bootloader by loading in, for example, this file: sx300_boot-13506.rfb that is also in the zip file mentioned above.
• Boringly, you can’t do this over http / https. You need to do it over TFTP. Which means you need to be onsite / connected over a stable VPN and have TFTP running on something.
• Reboot

Fix part 3

Now with 1.3.5.58 and updated bootloader – you can apply 1.4.11.5

• Set as active image
• reboot

then all that’s left to do is apologise to users who have had 3 switch reboots in quick succession.