HP StorageWorks Fabric OS 6.2 administrator guide (5697-0016, May 2009)

180 Managing virtual fabrics
Figure 18 Logical Fabric using ISLs and XISLs
By default, the physical ISL path is favored over the logical path (over the XISL) because it has a lower cost.
This behavior can be changed by configuring the cost of the dedicated physical ISL to match the cost of the
LISL.
Base switch ports on different chassis can be connected together to form a base fabric. Similar to other
Logical Switches, the base switches must have the same FID to be connected to one another. If the base
switches have different fabric IDs, the link between the switches is disabled.
It is a good practice to configure at least two XISLs, for redundancy.
The base fabric follows normal routing policies. As long as physical connectivity is available, the base
fabric maintains connectivity for the Logical Fabrics.
NOTE: If you disable a base switch, all of the logical ISLs are broken and the Logical Switches cannot
communicate with each other unless they are connected by a physical ISL.
Logical Fabric formation
Fabric formation is not based on connectivity, but is based on the FIDs of the Logical Switches. The basic
order of fabric formation is as follows:
1. The base fabric forms.
2. Logical Fabrics form when the base fabric is stable.
3. Traffic is initiated between the Logical Switches.
4. Devices start seeing each other.
Management model for Logical Switches
A Virtual-Fabrics-capable chassis is managed as a set of Logical Switches, not as a single switch.
There is one common IP address for the hardware that is shared by all of the Logical Switches in the
chassis.
All user operations are classified into one of the following:
• Chassis management operations
These are operations that span Logical Switch boundaries, such as:
• Logical Switch configuration (creating, deleting, modifying Logical Switches)
• Account management (determining which accounts can access which Logical Switches)
• FRU management (slotShow)
Base switch
Fabric ID 8
P9
Logical switch 7
Fabric ID 15
P7
Logical switch 6
Fabric ID 1
P4
Physical chassis 2
Base switch
Fabric ID 8
P6
Logical switch 3
Fabric ID 15
P5
Logical switch 2
Fabric ID 1
P2
P1
Physical chassis 1
P8
P6
P2
P1
XISL
Logical ISL
Logical ISL
Logical ISL
ISL
Logical switch 1
(Default logical switch)
Fabric ID 128
Logical switch 5
(Default logical switch)
Fabric ID 128