[ovs-dev] [PATCH] OVS: add some tips for kvm guest env

Ben Pfaff blp at nicira.com
Thu May 30 22:26:20 UTC 2013


Q: I created a bridge and added my Ethernet port to it, using commands
   like these:

       ovs-vsctl add-br br0
       ovs-vsctl add-port br0 eth0

   and as soon as I ran the "add-port" command I lost all connectivity
   through eth0.  Help!

A: A physical Ethernet device that is part of an Open vSwitch bridge
   should not have an IP address.  If one does, then that IP address
   will not be fully functional.

   You can restore functionality by moving the IP address to an Open
   vSwitch "internal" device, such as the network device named after
   the bridge itself.  For example, assuming that eth0's IP address is
   192.168.128.5, you could run the commands below to fix up the
   situation:

       ifconfig eth0 0.0.0.0
       ifconfig br0 192.168.128.5

   (If your only connection to the machine running OVS is through the
   IP address in question, then you would want to run all of these
   commands on a single command line, or put them into a script.)  If
   there were any additional routes assigned to eth0, then you would
   also want to use commands to adjust these routes to go through br0.

   If you use DHCP to obtain an IP address, then you should kill the
   DHCP client that was listening on the physical Ethernet interface
   (e.g. eth0) and start one listening on the internal interface
   (e.g. br0).  You might still need to manually clear the IP address
   from the physical interface (e.g. with "ifconfig eth0 0.0.0.0").

   There is no compelling reason why Open vSwitch must work this way.
   However, this is the way that the Linux kernel bridge module has
   always worked, so it's a model that those accustomed to Linux
   bridging are already used to.  Also, the model that most people
   expect is not implementable without kernel changes on all the
   versions of Linux that Open vSwitch supports.

   By the way, this issue is not specific to physical Ethernet
   devices.  It applies to all network devices except Open vswitch
   "internal" devices.

On Fri, May 31, 2013 at 06:19:19AM +0800, Zhi Yong Wu wrote:
> Yes
> 
> # ovs-vsctl show
> a9dc55a3-6755-4b91-957a-75cd9f27692e
>     Bridge "br0"
>         Port "em1"
>             Interface "em1"
>         Port "br0"
>             Interface "br0"
>                 type: internal
> 
> 
> On Fri, May 31, 2013 at 6:17 AM, Ben Pfaff <blp at nicira.com> wrote:
> > Is em1 on bridge br0?
> >
> > On Fri, May 31, 2013 at 05:59:32AM +0800, Zhi Yong Wu wrote:
> >> I tried to install OVS on my workstation, before starting kvm guest,
> >> its route table is below:
> >> default via 9.115.122.1 dev em1
> >> 9.115.122.0/24 dev em1  scope link
> >>
> >> then i started kvm guest:
> >> qemu-system-x86_64 -drive
> >> file=/home/zwu/misc/image/debian_squeeze_i386_desktop.qcow2,if=virtio
> >> -kernel arch/x86/boot/bzImage -append root=/dev/vda1 rw console=ttyS0
> >> -drive file=/btrfs.img,if=virtio -drive file=/btrfs1.img,if=virtio
> >> -drive file=/btrfs2.img,if=virtio -drive file=/btrfs3.img,if=virtio
> >> -nographic -S -s -m 10240M
> >>
> >> After kvm guest is started up, i tried to ping the host in kvm guest,
> >> but it failed.
> >> After i changed its route on the host as below:
> >> default via 9.115.122.1 dev br0
> >> 9.115.122.0/24 dev br0  scope link
> >> I again tried the host in kvm guest, and it can work.
> >>
> >> Is it clear to you?
> >>
> >>
> >> On Fri, May 31, 2013 at 5:47 AM, Ben Pfaff <blp at nicira.com> wrote:
> >> > I don't know.  I think that you would have to describe your scenario,
> >> > before we can say what (if anything) you are doing wrong.
> >> >
> >> > On Fri, May 31, 2013 at 05:45:06AM +0800, Zhi Yong Wu wrote:
> >> >> If i don't add such a route, it seem to not work, do i miss other something?
> >> >>
> >> >> On Fri, May 31, 2013 at 2:23 AM, Ben Pfaff <blp at nicira.com> wrote:
> >> >> > On Thu, May 30, 2013 at 06:40:26PM +0800, zwu.kernel at gmail.com wrote:
> >> >> >> From: Zhi Yong Wu <wuzhy at linux.vnet.ibm.com>
> >> >> >>
> >> >> >>   Add some tips for kvm guest; You know, it is a bit difficult
> >> >> >> to play for one starter if no such tips exist.
> >> >> >>
> >> >> >> Signed-off-by: Zhi Yong Wu <wuzhy at linux.vnet.ibm.com>
> >> >> >
> >> >> > It isn't normally necessary to add such a route.
> >> >>
> >> >>
> >> >>
> >> >> --
> >> >> Regards,
> >> >>
> >> >> Zhi Yong Wu
> >>
> >>
> >>
> >> --
> >> Regards,
> >>
> >> Zhi Yong Wu
> 
> 
> 
> -- 
> Regards,
> 
> Zhi Yong Wu



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