Tcpdump does not always work correctly with QETH driver in layer 3 mode

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Environment

SUSE Linux Enterprise Server 10

Situation

On IBM System z:
Tcpdump, and related tools using libpcap, do not always work correctly if tracing on qeth devices in layer 3 mode.

Resolution

The device either needs to be switched to layer 2 mode, or the fake_ll attribute to the qeth driver has to be set.

The latter can be done "on the fly" with the following command from a shell:

echo 1 > /sys/bus/ccwgroup/drivers/qeth/CCW/fake_ll

(replace CCW with the CCW of the device, for example: 0.0.fe30)

Additional Information

For more information please refer to the Device Driver manual (SC33-8289-03) at http://www-128.ibm.com/developerworks/linux/linux390/october2005_documentation.html

Disclaimer

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