S e n d d o c u m e n t a t i o n c o m m e n t s t o m d s f e e d b a c k - d o c @ c i s c o . c o m
12-33
Cisco MDS 9000 Family CLI Configuration Guide
OL-16184-01, Cisco MDS SAN-OS Release 3.x
Chapter 12 Configuring Interfaces
Buffer Credits
The receive BB_credit (
fcrxbbcredit
) value may be configured for each FC interface. In most cases,
you do not need to modify the default configuration.
Note
The receive BB_credit values depend on the module type and the port mode, as follows:
•
For 16-port switching modules and full rate ports, the default value is 16 for Fx mode and 255 for
E or TE modes. The maximum value is 255 in all modes. This value can be changed as required.
•
For 32-port switching modules and host-optimized ports, the default value is 12 for Fx, E, and TE
modes. These values cannot be changed.
•
For Generation 2 switching modules, see the
“Buffer Pools” section on page 14-8
.
Note
In the Cisco MDS 9100 Series, the left most groups of ports outlined in white (4 ports in the 9120 switch
and 8 ports in the 9140 switch) are full line rate like the 16-port switching module. The other ports (16
ports in the 9120 switch and 32 ports in the 9140 switch) are host-optimized like the 32-port switching
module. Each group of 4 host-optimized ports have the same rules as for the 32-port switching module.
Configuring Buffer-to-Buffer Credits
To configure BB_credits for a Fibre Channel interface, follow these steps:
Command
Purpose
Step 1
switch#
config t
switch(config)#
Enters configuration mode.
Step 2
switch(config)#
interface
fc1/1
switch(config-if)#
Selects a Fibre Channel interface and enters
interface configuration submode.
Step 3
switch(config-if)#
switchport fcrxbbcredit
default
Applies the default operational value to the
selected interface. The operational value depends
on the port mode. The default values are assigned
based on the port capabilities.
switch(config-if)#
switchport fcrxbbcredit 5
Assigns a BB_credit of 5 to the selected interface.
The range to assign BB_credits is between 1 and
255.
switch(config-if)#
switchport fcrxbbcredit 5
mode E
Assigns this value if the port is operating in E or
TE mode. The range to assign BB_credits is
between 1 and 255.
switch(config-if)#
switchport fcrxbbcredit 5
mode Fx
Assigns this value if the port is operating in F or
FL mode. The range to assign BB_credits is
between 1 and 255.
Step 4
switch(config-if#
do show int fc1/1
fc1/1 is up
...
16 receive B2B credit remaining
3 transmit B2B credit remaining
Displays the receive and transmit BB_credit
along with other pertinent interface information
for this interface.
Note
The BB_credit values are correct at the
time the registers are read. They are
useful to verify situations when the data
traffic is slow.
