Configuring Receive Data Field Size
You can configure the receive data field size for native Fibre Channel interfaces (but not for virtual Fibre
Channel interfaces). If the default data field size is 2112 bytes, the frame length will be 2148 bytes.
To configure the receive data field size, perform this task:
Procedure
Purpose
Command or Action
Enters configuration mode.
switch#
configuration terminal
Step 1
Selects a Fibre Channel interface and enters interface
configuration mode.
switch(config)#
interface fc
slot
/
port
Step 2
If this is a QSFP+ GEM, the
slot
/
port
syntax is
slot
/
QSFP-module
/
port
.
Note
Reduces the data field size for the selected interface to
2000 bytes. The default is 2112 bytes and the range is
from 256 to 2112 bytes.
switch(config-if)#
switchport
fcrxbufsize 2000
Step 3
Understanding Bit Error Thresholds
The bit error rate threshold is used by the switch to detect an increased error rate before performance degradation
seriously affects traffic.
The bit errors can occur for the following reasons:
•
Faulty or bad cable.
•
Faulty or bad GBIC or SFP.
•
GBIC or SFP is specified to operate at 1 Gbps but is used at 2 Gbps.
•
GBIC or SFP is specified to operate at 2 Gbps but is used at 4 Gbps.
•
Short haul cable is used for long haul or long haul cable is used for short haul.
•
Momentary synchronization loss.
•
Loose cable connection at one or both ends.
•
Improper GBIC or SFP connection at one or both ends.
A bit error rate threshold is detected when 15 error bursts occur in a 5-minute period. By default, the switch
disables the interface when the threshold is reached.
You can enter the
shutdown
/
no shutdown
command sequence to reenable the interface.
You can configure the switch to not disable an interface when the threshold is crossed.
Cisco Nexus 5500 Series NX-OS SAN Switching Configuration Guide, Release 7.x
20
OL-30895-01
Configuring Fibre Channel Interfaces
Configuring Fibre Channel Interfaces