Users Guide

318 Fabric OS Administrator’s Guide
53-1002920-02
Logical fabric overview
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FIGURE 30 Logical ISLs connecting logical switches
To use the XISL, the logical switches must be configured to allow XISL use. By default, they are
configured to do so; you can change this setting, however, using the procedure described in
“Configuring a logical switch to use XISLs” on page 333.
NOTE
It is a good practice to configure at least two XISLs, for redundancy.
You can also connect logical switches using a combination of ISLs and XISLs, as shown in
Figure 31. In this diagram, traffic between the logical switches in FID 1 can travel over either the
ISL or the XISL. Traffic between the other logical switches travels only over the XISL.
FIGURE 31 Logical fabric using ISLs and XISLs
By default, the physical ISL path is favored over the logical path (over the XISL) because the
physical path has a lower cost. This behavior can be changed by configuring the cost of the
dedicated physical ISL to match the cost of the logical ISL.