I'm trying to integrate my VMs into the same IP address space as an existing "real" network. I have a running version of OpenStack Grizzly with Quantum and OpenVSwitch.

For example, while an instance is running my OpenVSwitch bridges looks like this:

$ sudo ovs-vsctl show
e1bbbcb1-e20d-48e5-ae89-823c1a485625
    Bridge br-tun
        Port br-tun
            Interface br-tun
                type: internal
    Bridge br-int
        Port br-int
            Interface br-int
                type: internal
        Port "qvobf9997d8-9b"
            tag: 2
            Interface "qvobf9997d8-9b"
        Port "patch-br-eth1"
            tag: 2
            Interface "patch-br-eth1"
                type: patch
                options: {peer=patch-br-int}
        Port "tap48ad9b5d-6d"
            tag: 1
            Interface "tap48ad9b5d-6d"
                type: internal
        Port "int-br-eth1"
            Interface "int-br-eth1"
    Bridge br-ex
        Port br-ex
            Interface br-ex
                type: internal
    Bridge "br-eth1"
        Port "br-eth1"
            Interface "br-eth1"
                type: internal
        Port "phy-br-eth1"
            Interface "phy-br-eth1"
        Port patch-br-int
            Interface patch-br-int
                type: patch
                options: {peer="patch-br-eth1"}
        Port "eth1"
            Interface "eth1"
    ovs_version: "1.4.2"

And my quantum subnets look like this:

$ quantum subnet-list
+--------------------------------------+------------+-----------------+------------------------------------------------------+
| id                                   | name       | cidr            | allocation_pools                                     |
+--------------------------------------+------------+-----------------+------------------------------------------------------+
| 7e573fa2-c6db-42ae-93a9-b72a23e30000 | 50-network | 192.168.50.0/24 | {"start": "192.168.50.172", "end": "192.168.50.179"} |
+--------------------------------------+------------+-----------------+------------------------------------------------------+

So, in theory, the VM is connected via port qvobf9997d8-9b which is tagged as 2. Then the tag 2 is patched via a patch peer to br-eth1 (clearing the tag), which contains the "real" interface eth1. The host is assigned IP 192.168.50.250, which is on br-eth1.

What I would like to happen is:

1. The IP address is requested from DHCP server on startup and shown in Horizon.
2. All routing is then done across the two virtual bridges (br-int and br-eth1) to eth1 and out as though it was a physical machine on eth1 but with a different MAC address.

What actually happens is this:

1. Quantum assigns the first IP from the pool, even though I've specified "DHCP Enable: No". So OpenStack thinks the IP is 192.168.50.172
2. When the instance finished booting, udhcpc requests an IP from the DHCP server and receives a response, e.g. 192.168.50.186. So my patch is working, as far as DHCP is concerned.
3. However, I can't ping any other machine on the network, nor can the network ping the VM.

How do I tell Quantum to get the DHCP from an external DHCP server so that it shows up correctly in Horizon?

Why is it that, if I remove the subnet, no device is created for the VM?

And, is it possible to do a patch between a "real" switch and a virtual one like this? If so, how?