> # About Interop Mode

> Cisco NX-OS software supports the following four interop modes:

> - Mode 1— Standards based interop mode that requires all other vendors in the fabric to be in interop mode.
> - Mode 2—Brocade native mode (Core PID 0).
> - Mode 3—Brocade native mode (Core PID 1).
> - Mode 4—McData native mode.

> For information about configuring interop modes 2, 3, and 4, refer to the Cisco MDS 9000 Family Switch-to-Switch Interoperability Configuration Guide.

> Table 28-2 lists the changes in switch behavior when you enable interoperability mode. These changes are specific to switches in the Cisco MDS 9000 Family while in interop mode.

> Table 28-2 Changes in Switch Behavior When Interoperability Is Enabled
> Switch Feature | Changes if Interoperability Is Enabled
> --- | ---
> Domain IDs | Some vendors cannot use the full range of 239 domains within a fabric. Domain IDs are restricted to the range 97-127. This is to accommodate McData’s nominal restriction to this same range. They can either be set up statically (the Cisco MDS switch accept only one domain ID, if it does not get that domain ID it isolates itself from the fabric) or preferred. (If it does not get its requested domain ID, it accepts any assigned domain ID.)
> Timers | All Fibre Channel timers must be the same on all switches as these values are exchanged by E ports when establishing an ISL. The timers are F_S_TOV, D_S_TOV, E_D_TOV, and R_A_TOV.
> F_S_TOV | Verify that the Fabric Stability Time Out Value timers match exactly.
> D_S_TOV | Verify that the Distributed Services Time Out Value timers match exactly.
> E_D_TOV | Verify that the Error Detect Time Out Value timers match exactly.
> R_A_TOV | Verify that the Resource Allocation Time Out Value timers match exactly.
> Trunking | Trunking is not supported between two different vendor’s switches. This feature may be disabled on a per port or per switch basis.
> Default zone | The default zone behavior of permit (all nodes can see all other nodes) or deny (all nodes are isolated when not explicitly placed in a zone) may change.
> Zoning attributes | Zones may be limited to the pWWN and other proprietary zoning methods (physical port number) may be eliminated. Note Brocade uses the cfgsave command to save fabric-wide zoning configuration. This command does not have any effect on Cisco MDS 9000 Family switches if they are part of the same fabric. You must explicitly save the configuration on each switch in the Cisco MDS 9000 Family.
> Zone propagation | Some vendors do not pass the full zone configuration to other switches, only the active zone set gets passed. Verify that the active zone set or zone configuration has correctly propagated to the other switches in the fabric.
> VSAN | Interop mode only affects the specified VSAN. Note Interop modes cannot be enabled on FICON-enabled VSANs.
> TE ports and PortChannels | TE ports and PortChannels cannot be used to connect Cisco MDS to non-Cisco MDS switches. Only E ports can be used to connect to non-Cisco MDS switches. TE ports and PortChannels can still be used to connect an Cisco MDS to other Cisco MDS switches even when in interop mode.
> FSPF | The routing of frames within the fabric is not changed by the introduction of interop mode. The switch continues to use src-id, dst-id, and ox-id to load balance across multiple ISL links.
> Domain reconfiguration disruptive | This is a switch-wide impacting event. Brocade and McData require the entire switch to be placed in offline mode and/or rebooted when changing domain IDs.
> Domain reconfiguration nondisruptive | This event is limited to the affected VSAN. Only Cisco MDS 9000 Family switches have this capability—only the domain manager process for the affected VSAN is restarted and not the entire switch.
> Name server | Verify that all vendors have the correct values in their respective name server database.
> IVR | IVR-enabled VSANs can be configured in no interop (default) mode or in any of the interop modes.

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