Re: network/bridging problems

[Tom H <tomh0665@gmail.com>]

On Wed, Oct 2, 2013 at 3:40 PM, Ross Boylan <rossboylan@stanfordalumni.org> wrote:

>

> Arun made a suggestion that

>> Your 'physical' device eth0/eth2 or whatever needs to be added to the bridge.

> I believe that is done by the /etc/kvm/kvm-ifup script that is executed when I

> launch the virtual machine.

> It says, in part

>

> switch=$(ip route ls | \

>     awk '/^default / {

>           for(i=0;i<NF;i++) { if ($i == "dev") { print $(i+1); next; } }

>          }'

>         )

> # i.e, switch=eth2   (RB)

> 

> # only add the interface to default-route bridge if we

> # have such interface (with default route) and if that

> # interface is actually a bridge.

> # It is possible to have several default routes too

> for br in $switch; do

>     if [ -d /sys/class/net/$br/bridge/. ]; then

>         brctl addif $br "$1"

>         exit    # exit with status of brctl

>     fi

> done

> 

> # I think $1=tap0 as invoked, though maybe its br0 (RB)

> 

> Then again, I don't understand things well enough to know what adding

> something to a bridge means, or how that is accomplished.

"/etc/kvm/kvm-ifup" brings up tap0 ($1) and adds it to br0 ($switch/$br).

Since you're already doing the above via "/etc/network/interfaces", you should choose either to bring up your VM with "-net tap,script=no,downscript=no,..." or delete the pre-up and post-down lines from the br0 stanza in "/etc/network/interfaces":

auto br0

iface br0 inet dhcp

    bridge_ports all tap0

    bridge_stp off

    bridge_maxwait 0

    bridge_fd      0