XEN: Issues with multiple NICs

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Environment

SUSE Linux Enterprise Server 10

Situation

On systems with multiple NICs, DomU's are started and remain in a paused state.

Resolution

By default in Xen, there are 7 pair of vif and veth devices created. These devices are connected, that is each vifX,X is connected to a vethX. The vifX.X devices are connected to the bridge, and the vethX device is connected to a Dom0 or DomU.

For each physical device, a vethX and vifX.X pair is used. Under some circumstances, the number can run out. This has been observed in situations where there are bonded physical NICs, and systems that are running many virtual machines.

To fix this problem, increase the number of netloop devices.

Go to /etc/modprobe.d
Create and open a file named "netloop"
Add the following line (adjust 32 for your needs, larger or smaller):
options netloop nloopbacks=32
Save and close the file
Reboot

The community trying to move away from netloop. In future version of SLES it is anticipated that netloop will not be used anymore.

Disclaimer

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