[ovs-discuss] Same mac address of br0 and eth0

Jingfei Hu jingfei.hu at gmail.com
Wed Mar 21 05:04:20 UTC 2012


Hi, Ben,
In the last few days, I have spent my spare time on figuring out the reason
of ping DUP problem. Here is my result:
The network setting including netmask\default gateway etc. contains no
error. Following is the ip address setting and routing table of the host
and the guest:
--------------------------------------------------------------
Host:
IP address:
br0: 192.168.1.27 netmask 255.255.255.0
Routing table:
Destination     Gateway         Genmask         Flags Metric Ref    Use
Iface
0.0.0.0         192.168.1.1     0.0.0.0         UG    0      0        0 br0
192.168.1.0     0.0.0.0         255.255.255.0   U     0      0        0 br0

Guest:
IP address:
eth0: 192.168.1.26 netmask 255.255.255.0
Routing table:
Destination     Gateway         Genmask         Flags Metric Ref    Use
Iface
0.0.0.0         192.168.1.1     0.0.0.0         UG    0      0        0 eth0
169.254.0.0(link-local)     0.0.0.0         255.255.0.0     U     1000   0
       0 eth0
192.168.1.0     0.0.0.0         255.255.255.0   U     1      0        0 eth0
--------------------------------------------------------------
The ping DUP problem is still there.
Then in another machine, the same steps are executed with same host os and
same guest os, except that br0 is created using bridge-utils package, not
ovs-vsctl. When ping from the guest, the DUP problem has gone. So it seems
that the bridge created by ovs-vsctl is different than the bridge created
by bridge-utils package. Is that correct to say this problem is related to
ovs?

Cheers,

Hu Jingfei

3/19 Ben Pfaff <blp at nicira.com>

> I don't see how br0 and eth0 having the same MAC address would cause the
> behavior that you mention.  I would suggest following a conventional
> troubleshooting procedure instead of making this assumption.
>
> If you want us to help with that troubleshooting then you can start from
> the suggestions in REPORTING-BUGS.
>
> On Mon, Mar 19, 2012 at 10:12:17AM +0800, Jingfei Hu wrote:
> > Thanks, Ben,
> > But there is a problem here. The following commands have not changed:
> > ------------------------------------
> > sudo ovs-vsctl add-br br0
> > sudo ovs-vsctl set bridge br0 datapath_type=netdev
> > sudo ovs-vsctl add-port br0 eth0
> > sudo ovs-vsctl add-port br0 tap0
> > ------------------------------------
> > The tap0 interface is created using OpenVPN utility with following
> command:
> > ------------------------------------
> > sudo openvpn --mktun --dev tap0
> > ------------------------------------
> > Then I have created a VM using VirtualBox-4.1 and made the VM use the
> > Bridged Adapter tap0. IP address settings are:
> > ------------------------------------
> > In my host:
> > sudo ifconfig br0 192.168.1.24 netmask 255.255.255.0
> > eth0 and tap0 got no ip address assigned
> > In the guest, i.e. VM:
> > sudo ifconfig eth0 192.168.1.26 netmask 255.255.255.0
> > ------------------------------------
> > After that, my guest is able to reach the outside network, and the
> machine
> > which resides in the same LAN, says it's ip address is 192.168.1.14,
> could
> > also found my guest. The PROBLEM is:
> > when I ping the 192.168.1.14 from my guest, the ICMP reply is always
> > duplicated. I guess the cause is because the br0 has the same mac address
> > with eth0, but don't know how to solve it.
> > Any ideas will be appreciated. Sorry for the question in question, I
> should
> > ask it in one post.
> >
> > Cheers,
> > Hu Jingfei
> >
> >
> > 2012/3/18 Ben Pfaff <blp at nicira.com>
> >
> > > On Sun, Mar 18, 2012 at 10:46:36PM +0800, Jingfei Hu wrote:
> > > > I have installed OVS userspace program on Ubuntu Oneiric according to
> > > > INSTALL.Linux. Then I have added a bridge using following commands:
> > > >
> > > > sudo ovs-vsctl add-br br0
> > > > sudo ovs-vsctl set bridge br0 datapath_type=netdev
> > > > sudo ovs-vsctl add-port br0 eth0
> > > > sudo ovs-vsctl add-port br0 tap0
> > > >
> > > > Then I setup the bridge br0 as follows:
> > > > sudo ifconfig br0 192.168.1.24 netmask 255.255.255.0
> > > > After that, I check it with command ifconfig -a, finding that the
> mac br0
> > > > and eth0 have the same mac.
> > > >
> > > > Is it normal?
> > >
> > > Yes.
> > >
>
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