If your hardware is under maintenance, follow these steps:
Remember: The best free firmware is the one you already downloaded before your contract expired. Brocade Firmware Download Free
The B300 is EoL (since 2015). You might find v7.4 on file archives, but no support. If your hardware is under maintenance, follow these
: If your Brocade switch was purchased through an OEM like Dell , HPE , or NetApp , you should download the firmware from their respective support sites using your device's serial number or service tag. If your hardware is under maintenance
Brocade Firmware Download: How to Access and Update Fabric OS