> # 4-Port 10-Gbps Switching Module BB_Credit Buffers

> Table 14-9 lists the BB_credit buffer allocation for 4-port 10-Gbps switching modules.

> Table 14-9 4-Port 10-Gbps Switching Module BB_Credit Buffer Allocation
> BB_Credit Buffer Allocation Type | BB_Credit Buffers Per Port
> --- | ---
> Dedicated Rate Mode 10-Gbps Speed
> ISL1 | F port2
> Default BB_credit buffers | 250 | 16
> Maximum BB_credit buffers | 750 | 16
> Maximum BB_credit buffers on one of the ports with Enterprise license | 4095 |
> Total number of BB_credit buffers per module | 5488
> Default Performance buffers | 145 | 12
> Total number of performance buffers per module | 512 (shared)

> 1ISL = E port or TE port. 2Ports on the 4-port 10-Gbps cannot operate in FL port mode.

> Note The ports in the 4-port 10-Gbps switching module only support 10-Gbps dedicated rate mode. FL port mode and shared rate mode are not supported.

> The following considerations apply to BB_credit buffers on 4-port 10-Gbps switching modules:

> - BB_credit buffers for ISL connections can be configured from a minimum of 2 buffers to a maximum of 750 buffers.
> - BB_credit buffers for Fx port mode connections can be configured from a minimum of 2 buffers to a maximum of 750 buffers.
> - By default, 512 performance buffers are preallocated and are shared by all the ports. These buffers are configurable and the buffers are assigned to the port based on the availability of the buffers in the shared pool.
> - There are 2488 extra buffers available as extended BB_credits after allocating all the default BB_credit buffers for all the ports in ISL mode (5488 - (750 * 4)).

> Note Extended BB_credits are allocated across all ports on the switch. That is, they are not allocated by port group.

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