I'm having real trouble setting up networking with OpenStack. I had it partly working a while ago, but now I don't even get an IP address. I followed the main guide, but found it difficult to understand why things were being done - a list of instructions is all very well, but without explanations/background it makes debugging tough.

I've got a few questions I hope someone can help me with:

• responsibility for networking has mainly moved from nova to quantum. So the new way of doing things is solely in quantum - I can ignore anything network related in nova EXCEPT for metadata?

• is there a problem with rebooting - the bridges created in the guide don't come up automatically?

If I manually start the bridges and restart all the services I can bring up a virtual machine in the web GUI and see messages in /var/log/syslog - pairs of DHCPDISCOVER/DHCPOFFER. This goes on for some time until the VM gives up:

cloud-init-nonet waiting 120 seconds for a network device.
cloud-init-nonet gave up waiting for a network device.
ci-info: lo    : 1 127.0.0.1       255.0.0.0       .
ci-info: eth0  : 1 .               .               fa:16:3e:14:5a:69
route_info failed

The bridge setup (ovs-vsctrl show):

2df4b128-c977-48e2-aac9-596d386b7af1
   Bridge br-tun
       Port br-tun
           Interface br-tun
               type: internal
       Port patch-int
           Interface patch-int
               type: patch
               options: {peer=patch-tun}
   Bridge br-int
       Port "qr-03033815-f4"
           tag: 1
           Interface "qr-03033815-f4"
               type: internal
       Port br-int
           Interface br-int
               type: internal
       Port patch-tun
           Interface patch-tun
               type: patch
               options: {peer=patch-int}
       Port "qvocd51bf09-06"
           tag: 1
           Interface "qvocd51bf09-06"
       Port "tap5ec829c5-74"
           tag: 1
           Interface "tap5ec829c5-74"
               type: internal
   Bridge br-ex
       Port br-ex
           Interface br-ex
               type: internal
       Port "eth1"
           Interface "eth1"
   ovs_version: "1.4.0+build0"

• Interfaces: the "tap" interface seems to be the network node, while the "qr" interface is the controller. (Is this always the case? I'm just matching IP addresses when I do "ifconfig <interface>") The "qvoc" interface is the VM - I think - it has no IP address?

• Connectivity: all three of them are on the br-int bridge, so presumably they should all be able to talk to each other? (This is the same as if they were all plugged into a switch, right?)

• Is there a way to see where things are going wrong? It looks like the DHCPOFFER is never reaching the VM, which if they're all connected seems odd. Can I get a trace of packets being dropped or similar?