Comment 4 for bug 921838

On a hunch, I changed the magic byte to 0xfc. That now works. Libvirt (or whoever it is that is tweaking the address) sets the first byte to 0xfe, we get a 0xfc MAC. They're different, so all is OK. At least that's my theory.

Of course, if libvirt is tweaking the address, then we didn't need the change in the first place - sorry! Any idea if libvirt does this (or if not, how is the bridge address getting set to 0xfe?)

With 0xfc:

Guest ifconfig:
eth0 Link encap:Ethernet HWaddr fc:16:3e:63:63:3c
...

Host ifconfig:
ifconfig vnet3
vnet3 Link encap:Ethernet HWaddr fe:16:3e:63:63:3c