[openstack-dev] [l2gw] How to handle correctly unknown-dst traffic

Ricardo Noriega De Soto rnoriega at redhat.com
Fri Jun 23 08:57:47 UTC 2017


Hi Saverio,

Comments and questions inline:

First of all, which backend are you using? the l2gateway agent? or
something like OpenDaylight?? I'm currently testing an L2GW scenario with
ODL.


On Mon, May 29, 2017 at 4:54 PM, Saverio Proto <saverio.proto at switch.ch>
wrote:

> Hello,
>
> I have a question about the l2gw. I did a deployment, I described the
> steps here:
> https://review.openstack.org/#/c/453209/
>
> The unicast traffic works fine, but I dont understand what is the idea
> behind the handling of the broadcast traffic.
>
> Looking at openvswitch:
>
> I obtain the uuid with `vtep-ctl list-ls`
>
> vtep-ctl list-remote-macs <uuid>
>
> In this output I get an entry for each VM that has an interface in the
> L2 network I am bridging:
>
> ----
> # vtep-ctl list-remote-macs <uuid>
> ucast-mac-remote
>   fa:16:3e:c2:7b:da -> vxlan_over_ipv4/10.1.1.167
>
> mcast-mac-remote
> -----
>

The ucast-mac-remote table is filled with information that don't match your
comments. In my environment, I have created only one neutron network, one
l2gw instance and one l2gw connection. However, the mac reflected in that
table corresponds to the dhcp port of the Neutron network (I've checked the
mac on the dhcp namespace and it's the same).
I've created several VMs in different compute nodes and there is only one
line there. Could you check again the MAC address?


>
> The ucast-mac-remote entry is created by Openstack when I start a VM.
> (Also it is never removed when I delete the instance, is this a bug ? )
> Note that 10.1.1.167 is the IP address of the hypervisor where the VM is
> running.
>
> But mcast-mac-remote is empty. So this means that ARP learning for
> example works only in 1 way. The VM in openstack does not receive any
> broadcast traffic, unless I do manually:
>
> vtep-ctl add-mcast-remote ee87db33-1b3a-42e9-bc09-02747f8a0ad5
> unknown-dst  10.1.1.167
>
> This creates an entry in the table mcast-mac-remote and everything works
> correctly.
>

In my setup I get this automatically:

mcast-mac-remote
  unknown-dst -> vxlan_over_ipv4/192.0.2.6

If you're using the agent, it might be a bug.


>
>
> Now I read here http://networkop.co.uk/blog/2016/05/21/neutron-l2gw/
> about sending add-mcast-remote to the network nodes and then doing some
> magic I dont really understand. But I am confused because in my setup
> the tenant does not have a L3 router, so there is not a qrouter
> namespace for this network, I was planning to keep the network node out
> of the game.
>
> Is anyone running this in production and can shed some light ?
>

No production sorry, just PoC mode :-)

>
> thanks
>
> Saverio
>
>
>
>
>
>
>
>
>
>
>
> --
> SWITCH
> Saverio Proto, Peta Solutions
> Werdstrasse 2, P.O. Box, 8021 Zurich, Switzerland
> phone +41 44 268 15 15, direct +41 44 268 1573
> saverio.proto at switch.ch, http://www.switch.ch
>
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>
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-- 
Ricardo Noriega

Senior Software Engineer - NFV Partner Engineer | Office of Technology  |
Red Hat
irc: rnoriega @freenode
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