QLogic 7104-1M-CABLE Manual De Usuario

6–Configuring Drivers and Services
Other Configuration: Changing the MTU Size

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The Maximum Transfer Unit (MTU) is set to 4K and enabled in the driver by 
default. To change the driver default back to 2K MTU, add this line (as root) in 
/etc/modprobe.conf (or in 

/

etc/modprobe.conf.local on SLES):

options ib_ipath mtu4096=0

Restart the driver as described in 

.

The startup script for ib_ipath is installed automatically as part of the software 
installation, and normally does not need to be changed. It runs as a system 
service.

The primary configuration file for the InfiniPath driver ib_ipath and other 

modules and associated daemons is /etc/infiniband/openib.conf.

To use 4K MTU, set the switch to have the same 4K default. If you are using 
QLogic switches, the following applies:
„

For the Externally Managed 9024, use 4.2.2.0.3 firmware 
(9024DDR4KMTU_firmware.emfw) for the 9024 EM. This has the 4K 

MTU default, for use on fabrics where 4K MTU is required. If 4K MTU 
support is not required, then use the 4.2.2.0.2 DDR *.emfw file for 

DDR externally-managed switches. Use FastFabric to load the firmware 
on all the 9024s on the fabric.

„

For the 9000 chassis, use the most recent 9000 code 4.2.4.0.1. The 4K 
MTU support is in 9000 chassis version 4.2.1.0.2 and above. For the 
9000 chassis, when the FastFabric 4.3 (or later) chassis setup tool is 
used, the user is prompted for the MTU. FastFabric can then set that 
MTU in all the 9000 internally managed switches. The change will take 
effect on the next reboot. Alternatively, for the internally managed 9000s, 
the ismChassisSetMtu Command Line Interface (CLI) command can 

be used. This should be executed on every switch and both 
hemispheres of the 9240s.

For reference, see the FastFabric Users Guide Version 4.3 and the 
SIlverStorm 9000 CLI Reference Guide Version 4.2. Both are available from 
the QLogic web site.
For other switches, see the vendors’ documentation.