Brocade Network OS Administrator’s Guide v4.1.1 - Manual (Page 151)

the local interface is ISL disabled. Upon receiving such information, a neighbor switch stops its ISL
formation activity regardless of its current interface state.
NOTE
After you repair any segmented or disabled ISL ports, toggle the fabric ISL in order to propagate the
changes.
NOTE
A shutdown command on an operating ISL interface not only brings down the physical link but also its
FSPF adjacency. The main difference between a shutdown command and a no fabric isl enable
command is that the link stays up after a no fabric isl enable, while the link stays down after a
shutdown.
NOTE
Upon a fabric reconvergence that due to a topology change involving the ECMP fabric-isl path, there
may be sub-second flooding of known unicast traffic.
Disabling a fabric ISL
The no fabric isl enable command takes this interface out of the trunk group if this interface happens
to be currently part of the trunk. If you know and would like to fix the edge and fabric port assignments
on a switch, then this command allows you to completely turn off ISL formation logic and shorten any
link bring-up delays on edge ports.
1. Connect to the switch and log in using an account assigned to the admin role.
2. Enter the no fabric isl enable command.
Enabling a fabric trunk
NOTE
Trunks are not supported between the Brocade 8000 and the Brocade VDX 8770.
1. Connect to the switch and log in using an account assigned to the admin role.
2. Enter the fabric trunk enable command.
Disabling a fabric trunk
Fabric trunking is enabled by default. Enter the no fabric trunk enable command to revert the ISL back
to a standalone adjacency between two Brocade VCS Fabric switch.
Configuring broadcast, unknown unicast, and multicast forwarding
All switches in a Brocade VCS Fabric cluster share a single multicast tree rooted at the RBridge with the
lowest RBridge ID (domain ID). All broadcast, unknown unicast, and multicast traffic between two edge
RBridges is forwarded on this multicast tree inside the Brocade VCS Fabric. The multicast tree includes
all RBridges in the Brocade VCS Fabric.
Disabling a fabric ISL
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