Fabric OS Administrator’s Guide 215
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Logical fabric overview 10
You connect logical switches to other logical switches in two ways:
Using ISLs
Using base switches and shared ISLs

Logical fabric and ISLs

Figure 26 shows two physical chassis divided into logical switches.
In Figure 26, ISLs are used to connect the logical switches with fabric ID 1 and the logical switches
with fabric ID 15. The logical switches with fabric ID 8 are each connected to a non-Virtual Fabrics
switch. The two logical switches and the non-Virtual Fabrics switch are all in the same fabric, with
fabric ID 8.
FIGURE 26 Logical switches connected to other logical switches through physical ISLs
Figure 27 shows a logical representation of the configuration in Figure 26.
FIGURE 27 Logical switches connected to form logical fabrics
The ISLs between the logical switches are dedicated ISLs because they carry traffic only for a single
logical fabric. In Figure 26, Fabric 128 has two switches (the default logical switches), but they
cannot communicate with each other because they have no ISLs between them and they cannot
use the ISLs between the other logical switches.
Logical switch 8
Fabric ID 8
P9
Logical switch 7
Fabric ID 15
P7
Logical switch 6
Fabric ID 1 P4
Physical chassis 2
P8
P6
P5
P3
P2
P1
Switch
Logical switch 4
Fabric ID 8
P6
Logical switch 3
Fabric ID 15 P5
P4
Logical switch 2
Fabric ID 1 P3
P2
Logical switch 1
(Default logical switch)
Fabric ID 128
P1
Physical chassis 1
Logical switch 5
(Default logical switch)
Fabric ID 128
Fabric 128
Fabric 1
Fabric 15
Fabric 8
SW1
SW8
SW4
SW7
SW3
SW6
SW2
SW5