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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
• One port with dedicated rate mode and 4-Gbps speed plus
three ports with dedicated rate mode and 2-Gbps speed plus
two ports with shared rate mode and 4-Gbps speed (4:1 oversubscription)
• Six ports with dedicated rate mode and 2-Gbps speed
24-Port 8-Gbps Fibre Channel Module BB_Credit Buffers
Table 4-3 lists the BB_credit buffer allocation for the 24-port 8-Gbps Fibre Channel switching module.
The following guidelines apply to BB_credit buffers on 24-port 8-Gbps Fibre Channel switching
modules:
• BB_credit buffers allocated for ports 1 through 12 and 13 through 24 can be a maximum of 6000
each so that the load is distributed.
• 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.
Each port group on the 24-port 8-Gbps Fibre Channel switching module consists of three ports. The ports
in shared rate mode in a port group can have a maximum bandwidth oversubscription of 10:1 considering
that each port group has 12.8-Gbps bandwidth.
The following example configurations are supported by the 24-port 8-Gbps Fibre Channel switching
modules:
• Three ports with shared rate mode and 8-Gbps speed (2:1 oversubscription) (default)
• One port with dedicated rate mode and 8-Gbps speed plus
two ports with shared rate mode and 8-Gbps speed (4:1 oversubscription)
• One port with dedicated rate mode and 8-Gbps speed plus
one port with dedicated rate mode and 4-Gbps speed plus
one port with shared rate mode and 8-Gbps speed (10:1 oversubscription)
• Two ports with dedicated rate mode and 4-Gbps speed plus
one port with shared rate mode and 8-Gbps speed (2:1 oversubscription)
Ta b l e 4-3 24-Port 8-Gbps 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 500 32 32
Maximum BB_credit buffers 500
1
1. When connected to Generation 1 modules, reduce the maximum BB_credit allocation to 250.
500
1
32
Total Number of BB_Credit Buffers per Module
Ports 1 through 12 6000
Ports 13 through 24 6000
