We are seeing that a soft-reboot will keep the tap interface in a down state with the latest CentOS 7.3 / libvirt 2/ qemu-kvm-ev-2.6.0
(the interface always goes down but with the virsh start is should get back into an up state)
Doing a ip link up on the interface will make it work again.
Anyone else experiencing the same problem?
It could also be something that needs to be patched in the SDN software we use ( From libvirts perspective we use interface type='ethernet' )
With centos 7.2 the SDN worked fine though.
Would be great if we would know if this is a widespread problem or something in our specific setup.
For now we patched the nova code to work around it but it would be great to get it fixed properly.
Robert van Leeuwen