Whenever I set br0 to automatically start up on boot, it causes the system to hang - usually on a line that says something like "waiting 2 seconds for br0 to get ready" or "bound to x.x.x.x to br0 - renewal in xxxx" (i.e. during the boot sequence, before any graphical interfaces have initialised).

Using Debian Sid with KVM and virt-manager. I have no issues getting the bridge up an running once it's booted, and it works like a charm. The issue is that I want it automatically connect br0, just like you would a normal interface. I don't think this is such a ridiculous idea, but then again I don't have much experience in Linux networking.

I've tried just about every /etc/network/interfaces configuration that I've found, and all of them cause it to hang at boot, or don't start br0 automatically. The only thing I haven't explored extensively is the "pre-up" and "post-down" commands that I've seen occasionally, but I get the impression that these aren't necessarily needed. Because the system completely hangs and refuses to boot any further, it's quite a pain to force it to restart, boot up a rescue distro and remove any configuration in the interfaces file each time.

I've successfully been able to make it automatically start up by putting "ifup br0" in /etc/rc.local, but this causes a few other issues like shares not connecting and VNC not starting up. While I'm not quite at that stage yet, my worry is that my guests will be prevented from booting once I set them to automatically start up if I'm using this method.


2 Answers 2


This feels like a non-solution, but it seems to work. What I've done is made two interfaces files - interfaces_eth0 and interfaces_br0. Then I added

cp "/etc/network/interfaces_br0" "/etc/network/interfaces"
service networking restart
cp "/etc/network/interfaces_eth0" "/etc/network/interfaces"

to /etc/rc.local

Debian will boot, my shares connect and my guests have network access, even when set to automatically start up.

  • I'm not sure why, but at some point this stopped working.
    – user48052
    Commented Oct 10, 2013 at 0:43

Another solution that seems to be working so far involves the following. I created a script at /etc/init.d/network_fix which contains the following:

# Provides:          network_fix
# Required-Start:    $remote_fs $syslog $network
# Required-Stop:     $remote_fs $syslog $network
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: Fix network for KVM
# Description:       Resolve bridging bug causing hang on boot.
#! /bin/sh
# /etc/init.d/blah
cp -f /etc/network/interfaces_br0 /etc/network/interfaces
ifdown br0 eth0 eth1
ifup br0
cp -f /etc/network/interfaces_none /etc/network/interfaces
exit 0

And then refreshed my init.d with update-rc.d. /etc/network/interfaces_none contains loopback only, and /etc/network/interfaces_br0 contains the following:

auto lo
iface lo inet loopback

auto eth1
allow-hotplug eth1
iface eth1 inet dhcp

auto br0
iface br0 inet dhcp
        bridge_ports eth1
        bridge_stp off

At this point I had added an additional NIC, hence eth1.

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