Fibre Channel standards require a unique FC ID to be allocated to a N port attached to a Fx port in any switch. To conserve the number of FC IDs used, Cisco MDS 9000 Family switches use a special allocation scheme.
Based on the assigned FC ID, some HBAs assume that no other ports have the same area bits and domain. When a target is assigned with a FC ID that has the same area bits, but different port bits, the HBA fails to discover these targets. To isolate these HBAs in a separate area, switches in the Cisco MDS 9000 Family follow a different FC ID allocation scheme. By default, the FC ID allocation mode is auto . In the auto mode, only HBAs without interop issues are assigned FCIDs with specific ports bits. All other HBAs are assigned FC IDs with a whole area (port bits set to 0).
The three options to allocate FCID are auto (default), none, and flat.
Caution | Changes to FC IDs should be made by an administrator or individual who is completely familiar with switch operations. |