Update: Cumulus Networks have upstreamed a patch that sets a speed on a virtio_net enabled VM NIC.

Trying to configure a network bond in vagrant-libvirt environment?

Getting an error like this on the Linux host?

bond0: Warning: No 802.3ad response from the link partner for any adapters in the bond

If you get this error, confirm that the port speed is not available in sysfs.

$ ip link show eth1

3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000
    link/ether 52:54:00:27:16:f8 brd ff:ff:ff:ff:ff:ff

$ cat /sys/class/net/eth1/speed

cat: /sys/class/net/eth1/speed: Invalid argument

The fix is simple. Get the interface to report a speed. Change the vagrant libvirt default QEMU NIC driver, virtio, to another driver that reports a speed setting like e1000.

...
......
config.vm.define :compute1 do |node|
    node.vm.hostname = "compute1"
    node.vm.provider :libvirt do |domain|
      domain.memory = 512
      domain.nic_model_type = 'e1000'
    end
    node.vm.box = 'trusty64'
...
.....

Reload the vagrant setting using vagrant reload compute1 and the bond will form. Unfortunately LACP debugs in userspace do not exist. Only thing you can do to troubleshoot LACP on a Linux system, from a system administration perspective, is a sniffer trace, and reading Linux kernel source code.