Dear Jesse, Thanks for you reply. That makes sense.
I have one question, you said The routing table determines the interface that is used to output an IP packet (including GRE), regardless of whether that interface is a bridge or not. Is open Vswitch a layer 2 switch ? Where is the routing table residing ? And what can we do with that routing table ? Thanks very much. On Fri, Sep 30, 2011 at 3:45 PM, Jesse Gross <[email protected]> wrote: > On Thu, Sep 29, 2011 at 11:11 PM, terryxing <[email protected]> wrote: > > Dear Jesse, > > > > Thanks very much for your timely reply. It works. But I have some > confusion > > about the concept. > > > > I assign public ip for xenbr0 on each host, and private ip (172.16) for > > xenbr1 on each site. > > > > On Xenserver Host 1 > > ovs-vsctl add-port xenbr1 gre1 -- set interface gre1 type=gre > > options:remote_ip=129.X.X.X (public ip address on xenbr0 of xenserver > host > > 2) > > On Xenserver Host 2 > > ovs-vsctl add-port xenbr1 gre1 -- set interface gre1 type=gre > > options:remote_ip=198.X.X.X (public ip address on xenbr0 of xenserver > host > > 1) > > > > Note that we add gre port onto Xenbr1 but we use the ip of xenbr 0 as the > > remote accessible ip. I attached the vif onto the xenbr1 so that VMs on > two > > xenserver hosts can ping each other. It seems like the tunnel is > established > > between two Xenbr1 but they talk to each other through the public ip on > > Xenbr0. So, when packet sent from VM1, the packet will go from VIF to > > Xenbr1, then will the packet pass from xenbr1 to xenbr0 since it has to > go > > through the public ip and internet to arrive at Xenserver host 2, right ? > > Yes. > > > So, my final question is, how xenbr1 know that it has to forward this > > packet to xenbr0, and how these two xenbr1 and xenbr0 are connected ? > > The routing table determines the interface that is used to output an > IP packet (including GRE), regardless of whether that interface is a > bridge or not. > > > Also, what are the gre tunnel established between ? Xenbr1 to Xenbr1 ? or > > Xenbr0 to Xenbr0 ? > > The interfaces on xenbr1 are connected by the tunnel, xenbr0 is the > transport network. > -- Best regards, Tianyi Xing (邢天翼) PhD Student, Research & Teaching Associate SNAC:Secure Networking and Computing group School of Computing, Informatics, and Decision Systems Engineering Ira A. Fulton School of Engineering, Arizona State University Tempe, AZ 85281, USA Cell: (+1) 480-678-3090
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