I am following this tutorial: http://networkstatic.net/wp-content/uploads/2012/04/openvswitch.openflow.gre_.tutorial1.pdf

In brief: br0 is connected to the actual net, br1 is an isolated bridge to whom I attach multiple vms. Now I want to greate a gre tunnel between the two br1s as shown in the picture

enter image description here

Now, br0 is fine: I add my ethernet port and I am actually connected in my 192.168.1.x/24 LAN. For br1 I want a 192.168.100.x/24 family address, so to start I set:

ifconfig br1 netmask

Problem is that when I start my linux vm it just keep trying to connect to the eth0 without actually succeding! The interface is correctly configured as, if I ask for a

ovs-vsctl show

I get a "vnet0" port under br1 meaning that the vm is actually connected! But inside the guest operating system this connection does not take place. Any ideas?

edit: an ifconfig in the guest system tells me that the eth0 has no ip address associated. I tried to manually set it with:

ifconfig br1 netmask

but it still doesn't do the job.

1 Answer 1


In your setup, the path between VM1 and VM2 is intended to be forwarding Ethernet frames. Since the Ethernet layer is beneath the IP layer, the implication of that is, that nothing on the path between VM1 and VM2 is supposed to know what happens on the IP layer.

Only VM1 and VM2 will know about the IP layer. So assigning an IP address to br2 looks like a mistake, unless you want to connect the host as another node on the virtual segment.

If you only want those two VMs to be present on the virtual network segment, then the easiest way to configure IP is to simply configure eth0 inside each VM with a static IP address.

If you need many VMs on the segment, you might want to let one of the act as a DHCP server.

Your setup is prone to run into MTU issues. Those can be solved, but you need to get small packets through the connection before you start looking into possible MTU issues.

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