Ubuntu and the changing MAC address with bonding

With the ‘new’ style for configuring bonding under Ubuntu your bond device will not always have the same MAC address across reboots.

For example, you configure your bond in the /etc/network/interfaces file:

auto p9p1
iface p9p1 inet manual
        bond-master bond0

auto p10p1
iface p10p1 inet manual
        bond-master bond0

auto bond0
iface bond0 inet manual
        bond-slaves none
        bond-mode 4
        bond-miimon 100
        bond-updelay 5
        bond-downdelay 5

During boot, both interface p9p1 and p10p1 will be hot-plugged under bond0. The first device to be plugged into the bonding device determines which MAC address the bonded device gets.

Due to hardware timing it might be p9p1 OR p10p1 which is the first. This behavior makes the MAC address selection inconsistent between reboots and that might cause problems with:

  • DHCP for IPv4
  • IPv6 with SLAAC (Stateless Auto Configuration)
  • DHCPv6

This has been filed as bug #1288196 with Ubuntu, but no fix from that side so far.

The solutions for now:

auto p9p1
iface p9p1 inet manual
        bond-master bond0

auto p10p1
iface p10p1 inet manual
        pre-up sleep 5
        bond-master bond0

This makes sure p10p1 always comes online 5 seconds after p9p1.

But you can also set a static MAC address for the bonding device:

auto bond0
iface bond0 inet manual
        hwaddress fe:80:12:04:6d:6f
        bond-slaves none
        bond-mode 4
        bond-miimon 100
        bond-updelay 5
        bond-downdelay 5

Choose what you prefer or works best in your situation.

Published by

Wido den Hollander

I am the CTO at PCextreme B.V. and i will keep this blog just to post some interesting information about my daily work on Linux (and other) systems.