[ovs-discuss] Packet drops in OVS Bridge

chetandeep singh chetandeep.singhh at gmail.com
Wed Jul 20 23:04:39 UTC 2016


Hi Ben

I have a primary eth port eth2 and secondary Ethernet port eth3 that does
not have any ip assigned to the same. So machine does not get locked up.
The issue is that adding secondary port makes packets to get dropped in
bridge . Any ideas why ?

On Wednesday, July 20, 2016, Ben Pfaff <blp at ovn.org> wrote:

> On Wed, Jul 20, 2016 at 05:45:27PM -0500, chetandeep singh wrote:
> > I am trying to run some basic setup with OVS like creating a bridge and
> > adding taps for VM's in the bridge and a secondary ethernet port and then
> > eventually put the machine on the network. What I see is that if I do
> below
> > commands and add secondary eth3 port on the machine in the ovs bridge, I
> > see that packets start getting dropped. If I do ifconfig eth3, I dont see
> > any drops.
> >
> > Any idea why this might be happening in this case  ?
> >
> > ovs-vsctl add-br br0
> > ovs-vsctl add-port br0 eth3
> >
> > ifconfig br0
> > br0       Link encap:Ethernet  HWaddr 3C:A8:2A:0D:F9:31
> >           BROADCAST PROMISC MULTICAST  MTU:1500  Metric:1
> >           RX packets:0 errors:0 dropped:29 overruns:0 frame:0
> >           TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
> >           collisions:0 txqueuelen:0
> >           RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
>
> ### 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.
>


-- 
" In financial markets, the majority is always wrong "
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