Comment 1 for bug 1224007

In addition I've been able to set the MTU on the tagged bond using the following:

auto bond0.123
iface bond0.123 inet static
  address 192.168.122.68
  netmask 255.255.255.0
  gateway 192.168.122.1
  mtu 9000

As the documentation mentions (for both ipv4/ipv6):
   The static Method
       Options
              mtu size
                     MTU size

I think this would be the preferred way of setting this, however if I use this method I get:
"Waiting on network configuration" messages, which delay the boot by almost 2 minutes.