[ovs-discuss] Set up OpenFlow using OpenvSwitch

Yue ZHANG cassidy.zy at gmail.com
Tue Nov 9 11:36:15 UTC 2010

Hi, dear,

Thanks for your quickly reply.

I've insmod the OvS to replace original kernal bridge in the KVM host, and configured br0 and vif1(qemu param:-net tap,vlan=0,ifname=vif1) which is the interface of the KVM guest.

#ovs-vsctl add-br br0
#ovs-vsctl add-port br0 vif1

Then it seems like that:
#ovs-dpctl show br0
system at dp0:
 flows: xxxx
        port 0: br0 (internal)
        port 1: vif1               <--- The KVM guest interface

Then I ifconfig br0 with in the KVM host, and ifconfig eth0 with in the KVM guest.

I think the KVM guest( and br0( should be connected automatically, is it? But the tcpdump result is strange that the vif1 could send packet to br0, but could not receive any incoming packet.

If ping from kvm guest(2.2) to br0(2.1), br0 will receive arp request and return mac addr correctly, but the guest(2.2) will not receive the returned mac addr.
If ping from br0 to kvm guest, br0 sent arp request, but kvm guest(2.2) still received no packet.

There maybe something wrong, either the configuration of OvS or the KVM, it will be great help if you have some ideas, or give me some suggestions on how to debug, thanks!


cassidy.zy at gmail.com

> In the doc: 'The ovs-vsctl "set-controller" command can also be used in conjunction with ovs-vswitchd to set the controller for one or more bridges. We recommend using OpenFlow in this manner and in this case you should not run ovs-openflowd.' 
> Is that means there are two ways to get openflow set up? One is using ovs-openflowd configured by ovs-dpctl, the other is ovs-vswitchd configured by ovs-vsctl? 


> If so what is the differences between them? Ovs-vswitchd retrieves its configuration from database at startup but ovs-openflowd seems not? 

That is correct. More than that, though, ovs-vswitchd acts like a full-featured switch; it includes capabilities such as native VLAN support, mirroring (SPAN and RSPAN), and visibility (NetFlow and sFlow). ovs-openflowd, is really meant just to be an alternative for the OpenFlow reference implementation; it's just a simple wrapper around our OpenFlow library. 

> The document "Using Open vSwitch as a Simple OpenFlow Switch" is based on the ovs-openflowd, is it exactly the same with ovs-vswitchd? 

As I mention above, ovs-openflowd is meant to just be an alternative for the OpenFlow reference implementation. ovs-vswitchd provides many of the features expected from a more full-featured switch. Both support OpenFlow, though. 

> And it will be nice if you could give some detailed examples about how to test and verify if the configuration of openflow works. 

I'd recommend looking at ovs-controller (in the Open vSwitch distribution) or NOX (http://noxrepo.org). 


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