Brocade Fabric OS Administrators Guide (Supporting Fabric OS v7.3.0) - Manual (Page 270)

FIGURE 19 Switch before and after creating logical switches
Logical switches and fabric IDs
When you create a logical switch, you must assign it a fabric ID (FID). The fabric ID uniquely identifies
each logical switch within a chassis and indicates to which fabric the logical switch belongs. You
cannot define multiple logical switches with the same fabric ID within the chassis.
In the following figure, logical switches 2, 3, 4, and 5 are assigned FIDs of 1, 15, 8, and 20,
respectively. These logical switches belong to different fabrics, even though they are in the same
physical chassis. For example, you could not assign logical switch 5 a fabric ID of 15, because logical
switch 3 is already assigned FID 15 in the chassis.
The default logical switch is initially assigned FID 128. You can change this value later.
NOTE
Each logical switch is assigned one and only one FID. The FID identifies the logical fabric to which the
logical switch belongs.
Logical switches and fabric IDs
270 Fabric OS Administrators Guide
53-1003130-01