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Its format, for use with the xl toolstack, is documented at http://xenbits.xen.org/docs/unstable/man/xl.cfg.5.html.
Kernel parameters
Use the extras extra configuration item.
vif
vif (Default=[]; Value="type=TYPE, mac=MAC, bridge=BRIDGE, ip=IPADDR, script=SCRIPT," + \ "backend=DOM, vifname=NAME, rate=RATE, model=MODEL, accel=ACCEL" )
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