[Openstack-operators] Problem configuring openvswitch br-ex

Lorin Hochstein lorin at nimbisservices.com
Thu Jan 2 17:17:14 UTC 2014

For more details on this, here's the relevant text from the openvswitch FAQ:


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, you could run the commands below to fix up the

       ifconfig eth0
       ifconfig br0

   (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").

   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 Thu, Jan 2, 2014 at 9:45 AM, Narayan Desai <narayan.desai at gmail.com>wrote:

> I'm guessing that the installation instructions assume that you have
> different ethernet interfaces for the host and guests.
> If you want the host to use the same interface that is in use as a bridge,
> you'll need to add a virtual interface to the bridge that has the host's
> IP. FWIW, this isn't an openstack issue; it is common to OVS and linux
> bridging, with even without a hypervisor in the mix.
>  -nld
> On Thu, Jan 2, 2014 at 8:24 AM, Alvise Dorigo <alvise.dorigo at pd.infn.it>wrote:
>> Hi,
>> I'm configuring Neutron on a network node (a virtual machine) having two
>> NICs:
>> eth0:
>> eth1:
>> I've followed the official Openstack guide:
>> http://docs.openstack.org/havana/install-guide/install/yum/content/install-neutron.install-plug-in.ovs.html
>> When I issue the command (step 4)
>> ovs-vsctl add-port br-ex eth0
>> the terminal I'm working on freezes, and the connection to
>> is definitely lost, and I can't reconnect to it anymore from any other host.
>> I suspect there's some inaccuracy in the installation instructions, and
>> in addition I'm not an expert on bridge and interfaces stuff.
>> Can someone explain me what's wrong and if there's a better documentation
>> for a complete Neutron installation and configuration ?
>> thank you very much,
>> Alvise
>> _______________________________________________
>> OpenStack-operators mailing list
>> OpenStack-operators at lists.openstack.org
>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-operators
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Lorin Hochstein
Lead Architect - Cloud Services
Nimbis Services, Inc.
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