VM won't boot because of network not found

Just upgraded to 11 and delete the old images. I get the error below. After some googling, it seems I’m missing the default.xml file. Anyone know how to add it? Like create a new one?

Error starting domain: Network not found: no network with matching name ‘default’

Traceback (most recent call last):
File “/usr/share/virt-manager/virtManager/asyncjob.py”, line 96, in cb_wrapper
callback(asyncjob, *args, **kwargs)
File “/usr/share/virt-manager/virtManager/asyncjob.py”, line 117, in tmpcb
callback(*args, **kwargs)
File “/usr/share/virt-manager/virtManager/domain.py”, line 1162, in startup
self._backend.create()
File “/usr/lib/python2.7/dist-packages/libvirt.py”, line 866, in create
if ret == -1: raise libvirtError (‘virDomainCreate() failed’, dom=self)
libvirtError: Network not found: no network with matching name ‘default’

There is no default XML. The “Default” network should come with libvirt out if the box. You probably disabled or deleted it by mistake. Please check the available networks under virt-manager settings and report back.