Fabric Manager Users Guide, Version 6.1, Revision A - QLogic

3–Fabric Manager Configuration
Configuring the QLogic Fabric Manager
Table 3-7. Sm Multicast Routing Parameters (Continued)
Parameter
Default
Value
Description
RootSelectionAlgorithm LeastTotalCost Controls how the root switch for the multicast
spanning tree is selected. One of the
following algorithm names can be specified
to select the root switch for the spanning
tree (Names of algorithm are not
case sensitive).
LeastTotalCost — A switch with the
smallest sum of costs to other switches
will be selected.
LeastWorstCaseCost — A switch that
has the least worst case cost to other
switches will be selected.
SMNeighbor — The Switch next to the
SM will be selected.
LeastTotalCost and LeastWorst-
CaseCost tend to select a switch that is
more in the center of the fabric as the root
of the multicast spanning tree. With these
options, the information about the
selected switch is also communicated to
the standby SMs so that the multicast
spanning tree computed by the standby
SMs will match that of the master SM.
That way if the master SM fails over to a
standby SM, the multicast spanning tree
for the fabric will still remain the same
and the multicast forwarding tables in the
switches do not have to be reprogrammed.
The multicast traffic will not be
disrupted.
Since the SMNeighbor algorithm will
select the switch next to the SM, if a master
SM fails over to the standby, the spanning
tree computed by the standby SM
will differ from that of the master and the
multicast forwarding tables in the switch
will have to be reprogrammed which can
result in some disruptions to the multicast
traffic.
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