Fabric OS Administrator’s Guide 303
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Switch configurations for interoperability 14
In a Virtual Fabric, the logical switch used to communicate among different logical switches is
called the base switch and it must be in Brocade Native mode. If you set a logical switch to
interopmode 2 or interopmode 3, it cannot use the logical links between two logical switches if they
were connected using extended ISLs that were formed as part of the base fabric.
All logical switch-to-logical switch or Layer 2 switch connections must be through ISLs or dedicated
ISLs for switches in interopmode 2 or interopmode 3. You can change the interopmode of a logical
switch after it is created; it takes effect immediately without having to reboot the system.
All switches participating in a standard or logical fabric must be set to the same interopmode in
order to merge the fabric. For more information on Virtual Fabrics, see “Managing Virtual Fabrics”
on page 209.
NOTE
A dedicated ISL is a connection between two logical switches or other Layer 2 switches using E_Port
connections.

Switch configurations for interoperability

You can enter the interopMode command with the appropriate parameter to change the mode of
the switch to McDATA Fabric, McDATA Open Fabric, and Brocade Native modes. In v6.0.0 or later,
when McDATA Fabric interoperability mode is turned on, the OUI portion of the switch WWN is no
longer replaced with a McDATA OUI. The Brocade OUI is used. However, upgrading from Fabric OS
5.2.1_NI to Fabric OS v6.0.0 or later will be non-disruptive, preserving the McDATA OUI and the
given interopMode. Unless the switch is taken offline, and the interopMode is changed, or the OUI
is changed with the configure command, the McDATA OUI is preserved.
The following restrictions apply when changing from Brocade Native (IM0) to McDATA Fabric (IM2)
or McDATA Open Fabric Mode (IM3):
•Existing zone configurations, defined and effective, are erased. The switch assumes the zone
configuration from the fabric it joins, unless you create a new configuration.
•If you do not specify a Domain ID offset, the Domain ID default mode is used (offset 0x60).
The following restrictions apply when changing from McDATA Fabric (IM2) or McDATA Open Fabric
Mode (IM3) to Brocade Native Mode (IM0):
•Existing zone configurations, defined and effective, are erased. The switch assumes the zone
configuration from the fabric it joins, unless you create a new configuration.
ATTENTION
When interoperability mode is disabled, all configuration parameters return to their default states
and can be modified using the configure command.

Enabling McDATA Open Fabric mode

When configuring McDATA Open Fabric mode, avoid domain ID conflicts before fabric
reconfiguration. When configuring multiple switches, you should wait for a fabric reconfiguration
after adding or removing each switch. Every switch in the fabric must have a unique domain ID.