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Cisco MDS 9000 Family NX-OS Interfaces Configuration Guide
OL-29284-01, Release 6.x
Chapter 4 Configuring Interface Buffers
Information About Interface Buffers
The following considerations apply to BB_credit buffers on 12-port 4-Gbps switching modules:
BB_credit buffers for ISL connections can be configured from a minimum of 2 buffers to a
maximum of 250 buffers.
BB_credit buffers for Fx port mode connections can be configured from a minimum of 2 buffers to
a maximum of 250 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_credit buffers after allocating all the default
BB_credit buffers for all the ports in ISL mode (5488 - (250 * 12)).
Note Extended BB_credits are allocated across all ports on the switch. That is, they are not allocated
by port group.
Note By default, the ports in the 12-port 4-Gbps switching modules come up in 4-Gbps dedicated rate mode
but can be configured as 1-Gbps and 2-Gbps dedicated rate mode. Shared mode is not supported.
Total number of BB_credit buffers per module 5488
Total number of performance buffers per module 512 (shared)
1. ISL = E port or TE port.
Table 4-8 12-Port 4-Gbps Switching Module BB_Credit Buffer Allocation (continued)
BB_Credit Buffer Allocation Type
BB_Credit Buffers Per Port
Dedicated Rate Mode
4-Gbps Speed
ISL 1Fx Port