Well its early 2017 and it is time to upgrade servers still running Ubuntu 12.04. If these servers are virtualization hosts they most likely use a network bridge with a bonded network interface. This post describes a bonded network bridge configuration which works consistently on Ubuntu 12.04, 14.04 and 16.04 to avoid surprises of lost networking after upgrade.

So upgrade to Ubuntu 14.04 is straight forward and the bonding/bridge configuration works just the same as on 12.04. I cannot say the same for the update to 16.04.


To acually use bonding make sure you have ifenslave installed. For normal Linux network bridges, install bridge-utils as well.

sudo apt-get install ifenslave bridge-utils

Network configuration /etc/network/interfaces

auto lo
iface lo inet loopback

auto bond0
iface bond0 inet manual
	bond-slaves none
	bond-mode active-backup
	bond-miimon 100
	bond-downdelay 200
	bond-updelay 200
	post-up ifup eth0 eth1

iface eth0 inet manual
	bond-master bond0
	bond-primary eth0

iface eth1 inet manual
	bond-master bond0

auto br0
iface br0 inet static
	bridge_ports bond0
	bridge_fd 0
	bridge_hello 2
	bridge_maxage 0
	bridge_ageing 0
	bridge_maxwait 0
	bridge_stp off

Obviously replace the static network configuration details with your own.

The trick here is the post-up ifup eth0 eth1 on the bond0 interface. This will join the slaves on boot after 60 seconds while the bond waits for slaves to join while at the same time having no auto lines for the interfaces itself.

Make sure to have this configuration in place before the first reboot into Ubuntu 16.04 after update to avoid loosing network connectivity.

I publish this so it might help someone with the same issue.