> # 48-Port 8-Gbps Advanced Fibre Channel Module BB_Credit Buffers

> Table 14-1 lists the BB_credit buffer allocation for the 48-port 8-Gbps Advanced Fibre Channel switching module.

> Table 14-1 48-Port 8-Gbps Advanced Switching Module BB_Credit Buffer Allocation
> BB_Credit Buffer Allocation | BB_Credit Buffers Per Port
> --- | ---
> Dedicated Rate Mode 8-Gbps Speed | Shared Rate Mode 8-Gbps Speed
> ISL | Fx Port | Fx Port
> Default BB_credit buffers | 250 for 48 port 500 for 32 port | 32 | 32
> Maximum BB_credit buffers | 500 | 500 | 32

> .

> The following guidelines apply to BB_credit buffers on 32/48-port Advanced 8-Gbps Fibre Channel switching modules:

> - BB_credit buffers for ISL connections can be configured from a minimum of 2 buffers to a maximum of 500 buffers for dedicated rate mode.
> - BB_credit buffers for Fx port mode connections can be configured. The minimum is 2 buffers and the maximum of 500 buffers for dedicated rate mode or 32 buffers for shared rate mode.
> - Performance buffers are not supported on this module.
> - The buffers should not be allocated automatically.

> Each port group on the 32/48-port Advanced 8-Gbps Fibre Channel switching module consists of four/six ports. The ports in shared rate mode in a port group can have a maximum bandwidth oversubscription of 1.5:1 considering that each port group has 32-Gbps bandwidth. In case of 32 Port version, each port group of 4 ports has sufficient bandwidth (32 Gbps) to handle the line rate traffic without any oversubscription.

> The following example configurations are supported by the 48-port Advanced 8-Gbps Fibre Channel switching modules:

> - Six ports with shared rate mode and 8-Gbps speed (1.5:1 oversubscription) (default).
> - Two port with dedicated rate mode and 8-Gbps speed plus four ports with shared rate mode and 8-Gbps speed (2:1 oversubscription).
> - Two ports with dedicated rate mode and 8-Gbps speed plus four ports with shared rate mode and 8-Gbps speed (2:1 oversubscription) .
> - One port with dedicated rate mode and 8-Gbps speed plus three ports with dedicated rate mode and 4-Gbps speed plus two ports with shared rate mode and 8-Gbps speed (1.33:1 oversubscription).
> - Six ports with dedicated rate mode and 8-Gbps speed.

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