Hello Ingvar, You will need to be at FOS v8.2.1d or 8.2.2a in order to migrate over.  Here is the link to the release notes for Connectrix B Series Fabric OS version 9.0x which has some additional information. [URL]
Hi i am migrating from Brocade 6510 to 7720, i have been searching but cannot find out if having the old switch on firmware version 8.1.2j and the 7720 on 9.0.1a is supported so the zone information can flow from the old switch to the new?   also if anyone has some information or guide how to connect the new switch to the old fabric and if there is something to do or check before connecting ISL between them. BR Ingvar      
Migrate zones from 6510 to DS-7720