Hi, I am trying to configure two identical systems with the following setup. dom0: Centos 6 OS on Apple Xserve i7 server with PCI cards for 4GB FC (LSI FC949ES) and 10GB Ethernet (Intel 82598EB) dom1: Centos 5 OS with passthru mode of PCI 4GB FC and 10GB Ethernet (ixgbe and mptfc blacklisted in dom0) Everything starts ok, but networking in dom1 using the 10GB interface has extremely high rtt w/ping tests (20-30ms avg). I've tried a few tweaks I've discovered via googling, but nothing seems to help. (run libvirt as root, set privilege mode, etc) For validation, I have the same card in Dell hosts running Centos 6 natively and they get an avg rtt of .06ms or better. Furthemore the Dell will contact the dom1 but the connection has rtt avg times of about 6ms. With the ethernet interface on the motherboard of the Apple Xserve, I will see rtt times of .06ms within the dom1's, so I think this points to a problem with the Intel card passthru usage, perhaps interrupts handling?. Does anyone know if I need to set any special options for the ixgbe driver under libvirt? TIA, -- Laurence Schuler (Larry) Laurence.Schuler(a)nasa.gov Systems Support ADNET Systems, Inc Scientific Visualization Studio http://svs.gsfc.nasa.gov NASA/Goddard Space Flight Center, Code 606.4 phone: 1-301-286-1799 Greenbelt, MD 20771 fax: 1-301-286-1634 Note: I am not a government employee and have no authority to obligate any federal, state or local government to perform any action or payment.FC949ES