Brocade Network OS Administrator’s Guide v4.1.1 - Manual (Page 33)

Automatic ISL formation and hardware-based trunking
When a switch joins an Ethernet fabric, ISLs automatically form between directly connected switches
within the fabric.
If more than one ISL exists between two switches, then Brocade ISL trunks can form automatically. All
ISLs connected to the same neighboring Brocade switch attempt to form a trunk. The trunks are formed
only when the ports belong to the same port group. No user intervention is necessary to form these
trunks.
Refer to Configuring fabric interfaces on page 150 for information about enabling and disabling ISLs
and trunks.
Principal RBridge election
The RBridge with the lowest WWN in the Ethernet fabric is elected as the principal RBridge.
The role of the principal RBridge is to decide whether a new RBridge joining the fabric conflicts with any
of the RBridge IDs already present in the fabric. If a conflict arises, the principal RBridge keeps the
joining RBridge segmented.
Refer to Configuring a Brocade VCS Fabric on page 148 for information about setting the RBridge ID.
Brocade VCS Fabric technology use cases
This section describes the following use cases for Brocade VCS Fabric technology:
• Classic Ethernet
• Large-scale server virtualization
Classic Ethernet access and aggregation use case
Brocade VCS Fabric can be deployed in the same fashion as existing top-of-rack switches, as shown
below. In the right-most two server racks, a two-switch Ethernet fabric replaces the Ethernet switch at
the top of each rack.
Automatic ISL formation and hardware-based trunking
Network OS Administrator’s Guide 33
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