> # Combining Generation 1, Generation 2, Generation 3, and Generation 4 Modules

> Cisco MDS NX-OS Release 6.x and later supports combining Generation 1, Generation 2, Generation 3, and Generation 4 modules and switches with the following considerations:

> - MDS NX-OS Release 4.1(1) and later features are not supported on the following Generation 1 switches and modules:
> - Supervisor 1 module
> - 4-Port IP Storage Services module
> - 8-Port IP Storage Services module
> - MDS 9216 switch
> - MDS 9216A switch
> - MDS 9020 switch
> - MDS 9120 switch
> - MDS 9140 switch
> - Supervisor-1 modules must be upgraded to Supervisor-2 modules on the MDS 9506 and MDS 9509 Directors.
> - IPS-4 and IPS-8 modules must be upgraded to the MSM-18/4 Multiservice modules.
> - Fabric 1 modules must be upgraded to Fabric 2 modules on the MDS 9513 Director to use the 48-port or the 24-port 8-Gbps module.
> - Fabric 2 modules must be upgraded to Fabric 3 modules on the MDS 9513 Director to get the maximum backplane bandwidth of 256 Gbps.
> - Cisco Fabric Manager Release 4.x supports MDS SAN-OS Release 3.x and NX-OS 4.x in mixed mode through Interswitch Link (ISL) connectivity.

> Note When a Cisco or another vendor switch port is connected to a Generation 1 module port (ISL connection), the receive buffer-to-buffer credits of the port connected to the Generation 1 module port must not exceed 255.

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