Re: Bridging eth0/br0 & NetworkManager - can they coexist?

[Arun Khan <knura9@gmail.com>]

On Fri, Jun 29, 2012 at 7:32 PM, Steve Dowe <sd@warpuniversal.co.uk> wrote:
> Hello,
>
> I have absolutely no doubt that someone reading this list knows more
> than I do on this.. :)
>
> The issue I'm having, using wheezy, is that if I set up a bridged
> ethernet interface for eth0 (br0), as per instructions on the Debian
> wiki etc, NetworkManager can no longer manage my wired ethernet connection.
>
> If I edit /etc/NetworkManager/NetworkManager.conf and change
>
> [ifupdown]
> managed=false
>
> to
>
> [ifupdown]
> managed=true
>
> then eth0 and br0 both pick up the same IP address.
>
> This is my current /etc/network/interfaces:
>
> # The loopback network interface
> auto lo br0
> iface lo inet loopback
>
> # bridging
> iface br0 inet dhcp
>   bridge_ports eth0
>   bridge_stp off
>   bridge_maxwait 0
>   bridge_fd 0
>
>
> I must be missing something simple here.  Could anyone point me in the
> right direction please?  Has anyone got a working config?
>

When you use bridge:  To the best of my knowledge - the IP is assigned
to the bridge and *not* eth0 the physical interface.   eth0 should
*not* have any IP assigned to it.

I have run into this problem on my laptop to use Linux KVM VMs.

I have solved it by maintaining two /etc/networks/interfaces files like this

<quote>
$ ls -l /etc/network/interfaces*
lrwxrwxrwx 1 root root  17 Jun 25 10:27 /etc/network/interfaces ->
interfaces.debian
-rw-r--r-- 1 root root 686 May 21 21:38 /etc/network/interfaces.debian
-rw-r--r-- 1 root root  32 May 21 21:38 /etc/network/interfaces.ubuntu.orig
</quote>

When I need a bridge with tap interface I link the /etc/interfaces
file to interfaces.debian (NM reports error but I know networking is
fine ...

and when I need WiFI I link /etc/network/interfaces to interfaces.ubuntu.orig


<interfaces.debian>
$ cat /etc/network/interfaces.debian

... snip default stuff ....

# Set up interfaces manually, avoiding conflicts with, e.g., network manager
iface eth0 inet manual

# Bridge setup
auto br0

iface br0 inet dhcp
        pre-up /usr/sbin/tunctl -u <userid> -t tap0
        post-down /usr/sbin/tunctl -d tap0
        bridge_ports eth0 tap
</interfaces.debian>

<interfaces.ubuntu.orig>
$ cat /etc/network/interfaces.ubuntu.orig
auto lo
iface lo inet loopback

</interfaces.ubuntu.orig>

HTH
-- Arun Khan