How can I debug network-related issues?
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?