[ovs-discuss] Forwarding between Multiple interfaces Openflow

Aaron Rosen arosen at clemson.edu
Mon Feb 28 21:10:56 PST 2011


Hi Ben,

Yes you're right I pretty much have two separate bridges dp0 and dp1.
Is there any chance you could explain to me why this works?

dp1(130.127.39.235)gateway interface on computer
dp0(192.168.1.2)wireless card       <---- attached is a wireless
client (192.168.1.3)

If I send an IPIP packet with ip destination address to 192.168.1.3
that comes in on dp1 and then I leave the ip as 192.168.1.3 and send
the packet out on port OFPP_LOCAL (on dp1). The packet is actually be
seen on dp0 as a packet_in event (and i can remove the extra L3
header). Though, if i modify the packet to have the destination
address of 192.168.1.2 (dp0). The packet is never actually seen at the
dp0 interface.

Thanks,

Aaron




On Mon, Feb 28, 2011 at 11:37 PM, Ben Pfaff <blp at nicira.com> wrote:
> On Mon, Feb 28, 2011 at 8:04 PM, Aaron Rosen <arosen at clemson.edu> wrote:
>> Any idea what could be going on here:
>>
>> From 130.127.39.173 I'm pinging 192.168.1.2 (I've setup routes on the
>> network so that packets get to the right end points)
>>
>> I have dp1 (130.127.39.235) and dp0 (192.168.1.2) on the same computer. If I
>> run tcpdump on dp1 (which is the interface directly connected to the
>> internet) I see these packets .
>>
>> 22:58:17.462526 IP 130.127.39.173 > 192.168.1.2: ICMP echo request, id
>> 16684, seq 113, length 64
>> 22:58:17.613943 IP 130.127.39.173 > 192.168.1.2: ICMP echo request, id
>> 30764, seq 13, length 64
>>
>>
>> Though If I run tcpdump at dp0 I don't see these packets nor do I get
>> packet-in events for them. You said before that Open vSwitch isn't an IP
>> stack so does that mean tcpdump isn't going to be working there? Any idea
>> what I need to do to get packets to route between the two interfaces?
>> Shouldn't the linux routing tables handle this or not at all?
>
> tcpdump works on Linux network devices whether they have an IP address
> configured or not, so that isn't the problem.
>
> Do you want to do switching or routing between the two interfaces?  OVS is
> a switch, not a router, so if you want to do routing, then OVS is not the
> obvious choice, although it might usefully be a component of a solution.
> If you do want to do switching, then the Linux routing table is not
> relevant.
>
> If you want to set up a switch named br0 with interfaces eth0 and eth1,
> then starting from a clean setup you can run:
>  ovs-vsctl add-br br0
>  ovs-vsctl add-port br0 eth0
>  ovs-vsctl add-port br0 eth1
>
> You haven't really said what setup you are currently using, unless I
> missed it somewhere.  It sort of sounds like you have two separate
> bridges, one of which contains one Ethernet interface and the other
> of which contains the other.  That setup only makes sense if you are
> doing routing or tunneling or something else to span between one bridge
> and the other.
>



-- 
Aaron O. Rosen
Masters Student - Network Communication
306B Fluor Daniel
843.425.9777




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