Hi list! I got a suggestion.
I first posted this to kvm, but they said its a qemu issue. Just have a
new host server which several guests, set up networking via bridges, and
wondered why it didn't work reliable. Surprise, Mac-Address Konflikt!
For now I just hard-set some other Mac-Adresses in the Guests.... Random
Macs have their disadvantage of confusing dhcp servers, disturbing
ARP-Tables and so on.
So Suggestion: Make a Mac-Address of the guest hashed from the image
path+filename (if available). So the same "machine" always gets the same
mac-addresses, different "machine" get different macaddresses.