Hi Laine, Thank you for your reply, I just want to verify if these libvirt functions can be used to get the physical interface information when using kvm hypervisor. It's a good news that Red Hat Enterprise Linux will have a port of netcf library :) (P.S. I used RHEL5.5 and here are the errors which you can't see in the last mail: virsh command error: $virsh iface-list --all error: Failed to list active interfaces error: This function is not supported by the hypervisor： VirConnectNumOfInterface libvirt api call error: libvir: error : this function is not supported by the hypervisor: virConnectNumOfInterfaces org.libvirt.LibvirtException: this function is not supported by the hypervisor: virConnectNumOfInterfaces ) Best Regards, Fengdan Liu Tivoli ITCAM Solution, IBM China Software Development Lab, Tel: 13811762746 Email: liufengd(a)cn.ibm.com 3/F, Haohai Bldg., No.7, 5th Street, Shangdi, Haidian District, Beijing 100085, P.R.China Laine Stump <laine(a)laine.org&gt; Sent by: sendmail <justsendmailnothingelse(a)gmail.com&gt; 2010-07-01 00:19 To Feng Dan Liu/China/IBM@IBMCN cc libvir-list(a)redhat.com, Flo Kandefer <kandefer(a)us.ibm.com&gt;, Todd Gatts <tgatts(a)us.ibm.com&gt;, Bruce Anderson <andersbc(a)us.ibm.com&gt;, Jennifer Kuvlesky <jkuvlesk(a)us.ibm.com&gt; Subject Re: [libvirt] Ask for help about libvirt error: can't get physical interface data for kvm. On 06/30/2010 05:18 AM, Feng Dan Liu wrote: I saw both libvirt api and virsh commands support to get the physical interfaces data, but it always fail when I using them for KVM hypervisor. I was thought that it was due to the old version of libvirt/KVM hypervisor, but the error still exist when using the latest libvirt and kvm hypervisor. So I wonder if the following functions of libvirt haven't been implemented for KVM, could you pls help me get the answer about this? Thanks in advance! virConnectListInterfaces virConnectNumOfDefinedInterfaces virConnectNumOfInterfaces virConnectListDefinedInterfaces virInterfaceLookupByName Just to make sure you understand what these functions do - they are used to examine and configure the interfaces on the *physical host* that is running the hypervisor, not the virtual hosts (guests) running under that hypervisor. (One of the main motivations to add this API was to make it easier for management software to create bridge devices on the host, for use by the guests). These functions only work on a system that has the netcf library installed (regardless of hypervisor). Currently, only Fedora (12 and beyond), and Red Hat Enterprise Linux 6 (in beta) have a port of that library, although there has been some talk of a Suse port (and also someone was supposedly working on a Gentoo port last year, but I never saw anything more about that). netcf information can be found at https://fedorahosted.org/netcf, and there is a mailing list at https://fedorahosted.org/mailman/listinfo/netcf-devel. Patches to port netcf to other platforms are gratefully accepted. If you are running on a platform that doesn't have netcf support and would like to take on that task, please send mail to the list and we'll do what we can to help. (P.S. When you send mail to the libvirt list, you should probably try to avoid embedded graphics, as you have used to show your error message - many people reading the list are using text-only mail readers, and won't be able to see the graphical content.)