HP StorageWorks 2/24 FW 07.00.00/HAFM SW 08.06.00 McDATA Products in a SAN Env - Page 112

Planning Considerations for Fibre Channel Topologies 3 - For the Intrepid 10000 Director and Eclipse-series SAN routers, the firmware does not add a base offset to the numerically-assigned preferred Domain_ID. - For non-McDATA directors and switches, the product firmware may not add a base offset to the numerical preferred Domain_ID or may add a different hexadecimal base offset (not 60). As a consequence of this variable base offset and hexadecimal conversion, Domain_ID conflicts may exist in an open fabric, even if each participating director and switch is assigned a unique numerical Domain_ID. To determine the method of preferred Domain_ID assignment for a product, refer to the supporting OEM publications for the product or contact McDATA. NOTE: Do not assign Domain_ID 30 or Domain_ID 31 to a fabric element. In a routed SAN, these proxy Domain_IDs are assigned to routing domains. • Path selection - Directors and fabric switches are not manually configured with data transmission paths to each other. Participating fabric elements automatically exchange information to determine the fabric topology and resulting minimum-hop data transfer paths through the fabric. These paths route Fibre Channel frames between devices attached to the fabric and enable operation of the fabric services firmware on each director or switch. Paths are determined when the fabric topology is determined and remain static as long as the fabric does not change. If the fabric topology changes (elements are added or removed or ISLs are added or removed), directors and switches detect the change and define new data transfer paths as required. The algorithm that determines data transfer paths is distributive and does not rely on the principal switch to operate. Each director or switch calculates its own optimal paths in relation to other fabric elements. Only minimum-hop data transfer paths route frames between devices. If an ISL in a minimum-hop path fails, directors and switches calculate a new least-cost path (which may include more hops) and route Fibre Channel frames over that new path. Conversely, if the failed ISL is restored, directors and switches detect the original minimum-hop path and route Fibre Channel frames over that path. 3-26 McDATA Products in a SAN Environment - Planning Manual