Supported firmware for zoning
Zoning is supported only if all RBridges in the fabric are running Network OS 2.1 or later.
Connecting an RBridge running Network OS 2.0 to an RBridge running Network OS 2.1 or later merges the two networks only if the RBridge running Network OS 2.1 or later is in Brocade VCS Fabric mode and no zone database elements are defined or enabled.
A switch running Network OS v3.0.0 will segment if it is attached to a switch running Network OS v2.0.0 regardless of zoning configuration. A switch running Network OS v3.0.0 will join the fabric with a 2.1.x switch and zones will be merged, but the cluster will not form, so no further zoning commands will be allowed until all switches are upgraded to the same firmware version and the cluster has formed.
The Inter-Switch Links (ISLs) connecting the two RBridges will segment if the RBridge running Network OS 2.1 or later has any zone defined or enabled, or the default zone is set to No Access. Any such configuration requires automatic distribution of zoning configuration data, which is not compatible with RBridges running Network OS 2.0.