-if there are only 2 switches in fabric. and you remove the one switch(brocade). the other switch shall automatically become principle switch.
else you can check what is the current priority of the switch.
9148# show fcdomain
VSAN 1
The local switch is the Principal Switch.
Local switch run time information:
State: Stable
Local switch WWN: 20:01:00:0d:ec:2c:54:c1
Running fabric name: 20:01:00:0d:ec:2c:54:c1
Running priority: 128 <<<<<<<<<
Current domain ID: 0x11(17)
Local switch configuration information:
State: Enabled
FCID persistence: Enabled
Auto-reconfiguration: Disabled
Contiguous-allocation: Disabled
Configured fabric name: 20:01:00:05:30:00:28:df
Optimize Mode: Disabled
Configured priority: 128 <<<<<<<<
Configured domain ID: 0x00(0) (preferred)
lower the number , higer the priority.
To manually lower the number to make it principle switch:
http://www.cisco.com/en/US/docs/storage/san_switches/mds9000/sw/rel_3_x/configuration/guides/cli_3_3/domn.html#wp1113148
if you want to change the interop mode of a vsan.
the command is
"no vsan <#> interop 2"