[openstack-dev] [Neutron][dns]What the meaning of"dns_assignment" and "dns_name"?

Miguel Lavalle miguel at mlavalle.com
Wed Oct 14 22:39:15 UTC 2015

Zhi Chang,

You got all the steps correct. A few clarifications:

   1. Address is the ip address of my devstack VM. When you
   deploy Designate in devstack, it starts an instance of PowerDNS for you.
   Designate then pushes all its zones and records to that PowerDNS instance.
   When I say "dig my-instance.my-example.org @" I am
   instructing dig to direct the lookup to the DNS server @
   in other words, my PowerDNS instance
   2. For you to be able to execute the same steps in your devstack, you
      - The code in patchset https://review.openstack.org/#/c/212213/
      - The modified nova code in nova/network/neutronv2/api.py that I
      haven't pushed to Gerrit yet
      - Configure a few parameters in /etc/neutron/neutron.conf
      - Migrate the Neutron database, because I added columns to a couple
      of tables

Let me know if you want to try this in your devstack. If the answer is yes,
I will let you know when I push the nova change to gerrit. At that point, I
will provide detailed steps to accomplish point 2 above

Best regards


On Wed, Oct 14, 2015 at 12:53 AM, Zhi Chang <changzhi at unitedstack.com>

> Hi, Miguel
>     Thank you so much for your reply. You are so patient!
>     After reading your reply, I still have some questions to ask you. :-)
>     Below, is my opinion about the http://paste.openstack.org/show/476210/,
> please read it and tell me whether I was right.
>     (1). Define a DNS domain
>     (2). Update a network's "dns_domain" attribute to the DNS domain which
> defined in the step1
>     (3). Create a VM in this network. The instance's port will assign
> instance's hostname to it's dns_name attribute
>     (4). Create a floating IP for this VM
>     (5). In Designate, there will be generate a new A record. This record
> is a link between floating IP and dns_name+domain_name. Just like your
> record: deec921d-b630-4479-8932-c5ec7c530820 | A |
> my-instance.my-example.org. |
>   (6). I am don't understand where the IP address "" comes
> from. I think this address is a public DNS, just like Does it
> right?
>    (7). I can dig "my-instance.my-example.org." by a public DNS. And the
> result is the floating IP.
> Does my understanding was right?
> Hope For Your Reply.
> Thanks
> Zhi Chang
> ------------------ Original ------------------
> *From: * "Miguel Lavalle"<miguel at mlavalle.com>;
> *Date: * Wed, Oct 14, 2015 11:22 AM
> *To: * "OpenStack Development Mailing List (not for usage questions)"<
> openstack-dev at lists.openstack.org>;
> *Subject: * Re: [openstack-dev] [Neutron][dns]What the meaning
> of"dns_assignment" and "dns_name"?
> Zhi Chang,
> Thank you for your questions. We are in the process of integrating Neutron
> and Nova with an external DNS service, using Designate as the reference
> implementation. This integration is being achieved in 3 steps. What you are
> seeing is the result of only the first one. These steps are:
> 1) Internal DNS integration in Neutron, which merged recently:
> https://review.openstack.org/#/c/200952/. As you may know, Neutron has an
> internal DHCP / DNS service based on dnsmasq for each virtual network that
> you create. Previously, whenever you created a port on a given network,
> your port would get a default host name in dnsmasq of the form
> 'host-xx-xx-xx-xx.openstacklocal.", where xx-xx-xx-xx came from the port's
> fixed ip address "xx.xx.xx.xx" and "openstacklocal" is the default domain
> used by Neutron. This name was generated by the dhcp agent. In the above
> mentioned patchset, we are moving the generation of these dns names to the
> Neutron server, with the intent of allowing the user to specify it. In
> order to do that, you need to enable it by defining in neutron.conf the
> 'dns_domain' parameter with a value different to the default
> 'openstacklocal'. Once you do that, you can create or update a port and
> assign a value to its 'dns_name' attribute. Why is this useful? Please read
> on.
> 2) External DNS integration in Neutron. The patchset is being worked now:
> https://review.openstack.org/#/c/212213/. The functionality implemented
> here allows Neutron to publish the dns_name associated with a floating ip
> under a domain in an external dns service. We are using Designate as the
> reference implementation, but the idea is that in the future other DNS
> services can be integrated.. Where does the dns name and domain of the
> floating ip come from? It can come from 2 sources. Source number 1 is the
> floating ip itself, because in this patchset we are adding a dns_name and a
> dns_domain attributes to it. If the floating ip doesn't have a dns name and
> domain associated with it, then they can come from source number 2: the
> port that the floating ip is associated with (as explained in point 1,
> ports now can have a dns_name attribute) and the port's network, since this
> patchset adds dns_domain to networks.
> 3) Integration of Nova with Neutron's DNS. I have started the
> implementation of this and over the next few days will push the code to
> Gerrit for first review. When an instance is created, nova will request to
> Neutron the creation of the corresponding port specifying the instance's
> hostname in the port's 'dns_name' attribute (as explained in point 1). If
> the network where that port lives has a dns_domain associated with it (as
> explained in point 2) and you assign a floating ip to the port, your
> instance's hostname will be published in the external dns service.
> To make it clearer, here I walk you through an example that I executed in
> my devstack: http://paste.openstack.org/show/476210/
> As mentioned above, we also allow the dns_name and dns_domain to be
> published in the external dns to be defined at the floating ip level. The
> reason for this is that we envision a use case where the name and ip
> address made public in the dns service are stable, regardless of the nova
> instance associated with the floating ip.
> If you are attending the upcoming Tokyo summit, you could attend the
> following talk for further information:
> http://openstacksummitoctober2015tokyo.sched.org/event/5cbdd5fb4a6d080f93a5f321ff59009c#.Vh3KMZflRz2
> Looking forward to see you there!
> Hope this answers your questions
> Best regards
> Miguel Lavalle
> On Tue, Oct 13, 2015 at 9:58 AM, Zhi Chang <changzhi at unitedstack.com>
> wrote:
>> Hi, all
>>     I install the latest devstack and create a vm by nova. I get the
>> port's info which created by Neutron. I'm confused that what the meaning of
>> column "dns_assignment" and column "dns_name".
>>     First, column "dns_assignment" is a read-only attribute. What is it
>> used for? I think that this column is useless except shows DNS infomation
>> (include hostname, ip, fqdn). Does my thought right?
>>     Second, I don't quite understand what the meaning of column
>> "dns_name". I can update this column, but there is nothing happen when my operation
>> was done. In other words, this column has no change when I run "neutron
>> port-update xxx --dns_name=test". What the column "dns_name" use for?
>> Thanks
>> Zhi Chang
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