[rhos-list] Quantum Query:

[Shixiong Shang (shshang)]

Hi, Bob:

Thanks a ton for the reply (even I didn't raise the original question). It is very informational and educational. I read it many many times and it helps me clarify some confusion as you rightly pointed out. But I still have some questions and would like to make sure I precisely understand what you mean here.

1) In my current setup, I created external network net_ext, but later on I realized that router cannot ping its default gateway. I have to manually set the tag for qg- port on br-eth3 (mapped to physnet3) to 311 in order to make the ping happen. Based on your explanation, is it because provider attributes in "quantum net-create" command are ignored by L3 agent, so no VLAN tagging takes place?

quantum net-create --tenant-id 110ea394615d4cefa9824cf8829c841f net_ext --provider:network_type vlan --provider:physical_network physnet3 --provider:segmentation_id 311 --router:external=True


2) When provider attributes in "quantum net-create" command are ignored by L3 agent, there is no linkage between external network/subnet to a specific bridge, and that is why we need to manually put in "external_network_bridge" in l3_agent.ini. Is that correct?

3) If 1) and 2) are correct, then one limitation I can see by using "provider external network" approach is, we can only have a single external bridge and a single external network on quantum network node in order to formulate 1-to-1 mapping. Is that correct?

4) In "external bridge" approach, is there specific reason you recommend using network_type of local?

Thanks a lot again!

Shixiong





On Jun 21, 2013, at 12:43 PM, Robert Kukura <rkukura at redhat.com<mailto:rkukura at redhat.com>>
 wrote:

There are two different approaches to connecting a router to an external
network. One uses an external bridge (br-ex), and bypasses the L2 agent.
The other uses a provider external network, and the interface driver and
L2 agent handle this network just like any other network (using br-int).
To use a provider external network, just set:

external_network_bridge =

in /etc/quantum/l3_agent.ini and create the external network with the
provider attributes describing it (typically provider:network_type is
flat or vlan).

The provider external network approach is more flexible - the external
network can be a VLAN and can coexist on the same physical network with
tenant networks, VMs can be connected directly to the external network,
different routers can use different external networks, etc.. Also, this
approach works with both openvswitch and linuxbridge, whereas the
external bridge approach only works with openvswitch.

I see that chapter 5 in the referenced upstream documentation may be
adding to the confusion by sort of mixing the two approaches. It is
specifying the provider details on the external network:

quantum net-create --tenant-id $tenant public01 \
--provider:network_type flat \
--provider:physical_network physnet1 \
--router:external=True

but the l3 agent is accessing it via br-ex where the provider details
don't matter because the l2 agent is bypassed. If using the external
bridge, I'd recommend creating the external network with
provider:network_type of local as is shown in appendix A:

quantum net-create Ext-Net --provider:network_type local \
--router:external true

Hope this helps,

-Bob

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