How to troubleshoot a macvtap network in kvm/virt-manager

http://askubuntu.com/questions/377413/how-to-troubleshoot-a-macvtap-network-in-kvm-virt-manager

2 down vote favorite 1

I have a virtual machine running under qemu-kvm, on a 13.10 host.I am using virt-manager to define the machine, and I have added a virtual NIC, using the new macvtap driver. I have the following definition: <interface type='direct'> <mac address='52:54:00:1f:dd:c4'/> <source dev='eth0' mode='bridge'/> <model type='virtio'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/> </interface> On the host machine, I can see that the tap interface is created: $ip link 5: macvtap0@eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN mode DEFAULT qlen 500 link/ether 52:54:00:1f:dd:c4 brd ff:ff:ff:ff:ff:ff $ls /dev/tap5 /dev/tap5 But in the virtual machine, interface eth0 is unable to access the network. dhcp fails. Static configuration obviously works, but then I cannot ping anything. I have no iptables rules, neither on the host, nor in the virtual machine. So, how can I troubleshoot this problem ?

1 down vote accepted

I have same problem with Ubuntu 13.10, I also update to 14.04 development branch to try but still does not work. I do not know a good way debug, for my problem, I found eth0 does not enter promiscuous mode, I can not find message like device eth0 entered promiscuous mode in dmesg output. So I force eth0 into promiscuous mode, the problem then disappears. This is what I did: Force eth0 into promiscuous mode:sudo ifconfig eth0 promisc Use virt-manager to start the VM ifconfig -a and ping outside to see whether it works for you. I do not know why libvirt does not put eth0 into promiscuous mode, maybe a bug of it.