# How To Manage PTR Records

## PTR Record Basics

PTR records provide a reverse mapping from a single IP or set of IP addresses to a fully qualified domain name (FQDN). For example,

    $ dig -x 192.0.2.12 +short
    example.org.

The way this works in the DNS system is through the in-addr.arpa. zone. For example

    $ dig example.org +short
    192.0.2.12
    $ dig -x 192.0.2.12
    ; <<>> DiG 9.9.5-3ubuntu0.1-Ubuntu <<>> -x 192.0.2.12
    ;; global options: +cmd
    ;; Got answer:
    ;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 3431
    ;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1

    ;; OPT PSEUDOSECTION:
    ; EDNS: version: 0, flags:; udp: 4000
    ;; QUESTION SECTION:
    ;12.2.0.192.in-addr.arpa.   IN      PTR      example.org.

    ;; AUTHORITY SECTION:
    12.2.0.192.in-addr.arpa. 3600 IN     NS      ns1.example.org.

    ;; Query time: 40 msec
    ;; SERVER: 127.0.0.1#53(127.0.0.1)
    ;; WHEN: Fri Feb 20 19:05:44 UTC 2015
    ;; MSG SIZE  rcvd: 119

In the question section we see the address being requested from the DNS system as 12.2.0.192.in-addr.arpa.. As you can see, the IP address has been reversed in order to function similarly to a domain name where the more specific elements come first. The reversed IP address is then added to the in-addr.arpa. domain, at which point the DNS system can perform a simple look up to find any PTR records that describe what domain name, if any, maps to that IP.

## Create a PTR Record in Designate

To create a PTR record in Designate we need a in-addr.arpa. zone that will receive the actual PTR record

### Using the V2 API and the OpenStack CLI

To begin let’s create a zone that we want to return when we do our reverse lookup.

    POST /v2/zones HTTP/1.1
    Accept: application/json
    Content-Type: application/json

    {
      "name": "example.org.",
      "email": "admin@example.org",
      "ttl": 3600,
      "description": "A great example zone"
    }

Here is the JSON response describing the new zone.

    HTTP/1.1 202 Accepted
    Location: http://127.0.0.1:9001/v2/zones/251fbde4-6eb8-44e6-bc48-e095f1763a1f
    Content-Length: 476
    Content-Type: application/json; charset=UTF-8
    X-Openstack-Request-Id: req-bfcd0723-624c-4ec2-bbd5-99e985efe8db
    Date: Tue, 02 Jun 2020 17:24:10 GMT
    Connection: keep-alive

    {
      "id": "251fbde4-6eb8-44e6-bc48-e095f1763a1f",
      "pool_id": "794ccc2c-d751-44fe-b57f-8894c9f5c842",
      "project_id": "123d51544df443e790b8e95cce52c285",
      "name": "example.org.",
      "email": "admin@example.org",
      "description": "A great example zone",
      "ttl": 3600,
      "serial": 1591118650,
      "status": "PENDING",
      "action": "CREATE",
      "version": 1,
      "attributes": {},
      "type": "PRIMARY",
      "masters": [],
      "created_at": "2020-06-02T17:24:10.000000",
      "updated_at": null,
      "transferred_at": null,
      "links": {
        "self": "http://127.0.0.1:9001/v2/zones/251fbde4-6eb8-44e6-bc48-e095f1763a1f"
      }
    }

Using the CLI:

    $ openstack zone create --email admin@example.org \
        --description "A great example zone" --ttl 3600 example.org.
    +----------------+--------------------------------------+
    | Field          | Value                                |
    +----------------+--------------------------------------+
    | action         | CREATE                               |
    | attributes     |                                      |
    | created_at     | 2020-06-02T17:24:10.000000           |
    | description    | A great example zone                 |
    | email          | admin@example.org                    |
    | id             | 251fbde4-6eb8-44e6-bc48-e095f1763a1f |
    | masters        |                                      |
    | name           | example.org.                         |
    | pool_id        | 794ccc2c-d751-44fe-b57f-8894c9f5c842 |
    | project_id     | 123d51544df443e790b8e95cce52c285     |
    | serial         | 1591118650                           |
    | status         | PENDING                              |
    | transferred_at | None                                 |
    | ttl            | 3600                                 |
    | type           | PRIMARY                              |
    | updated_at     | None                                 |
    | version        | 1                                    |
    +----------------+--------------------------------------+

Note

The status is PENDING. If we make a GET request to the self field in the zone, it will most likely have been processed and updated to ACTIVE.

Now that we have a zone we would like to use for our reverse DNS lookup, we need to add an in-addr.arpa. zone that includes the IP address we want to look up.

Let’s configure 192.0.2.11 to return our example.org. domain name when we do a reverse look up.

    POST /v2/zones HTTP/1.1
    Accept: application/json
    Content-Type: application/json

    {
      "name": "11.2.0.192.in-addr.arpa.",
      "email": "admin@example.org",
      "ttl": 3600,
      "description": "A in-addr.arpa. zone for reverse lookups"
    }

As you can see, in the name field we’ve reversed our IP address and used that as a subdomain in the in-addr.arpa. zone.

Here is the response.

    HTTP/1.1 202 Accepted
    Location: http://127.0.0.1:9001/v2/zones/f5546034-b27e-4326-bf9d-c53ed879f7fa
    Content-Length: 512
    Content-Type: application/json; charset=UTF-8
    X-Openstack-Request-Id: req-4e691123-045e-4f8e-ae50-b5eabb5af3fa
    Date: Tue, 02 Jun 2020 17:32:46
    Connection: keep-alive

    {
      "id": "f5546034-b27e-4326-bf9d-c53ed879f7fa",
      "pool_id": "794ccc2c-d751-44fe-b57f-8894c9f5c842",
      "project_id": "123d51544df443e790b8e95cce52c285",
      "name": "11.2.0.192.in-addr.arpa.",
      "email": "admin@example.org",
      "description": "A in-addr.arpa. zone for reverse lookups",
      "ttl": 3600,
      "serial": 1591119166,
      "status": "PENDING",
      "action": "CREATE",
      "version": 1,
      "attributes": {},
      "type": "PRIMARY",
      "masters": [],
      "created_at": "2020-06-02T17:32:47.000000",
      "updated_at": null,
      "transferred_at": null,
      "links": {
        "self": "http://127.0.0.1:9001/v2/zones/f5546034-b27e-4326-bf9d-c53ed879f7fa"
      }
    }

Using the CLI:

    $ openstack zone create --email admin@example.org \
        --ttl 3600 --description "A in-addr.arpa. zone for reverse lookups" \
        11.2.0.192.in-addr.arpa.
    +----------------+------------------------------------------+
    | Field          | Value                                    |
    +----------------+------------------------------------------+
    | action         | CREATE                                   |
    | attributes     |                                          |
    | created_at     | 2020-06-02T17:32:47.000000               |
    | description    | A in-addr.arpa. zone for reverse lookups |
    | email          | admin@example.org                        |
    | id             | f5546034-b27e-4326-bf9d-c53ed879f7fa     |
    | masters        |                                          |
    | name           | 11.2.0.192.in-addr.arpa.                 |
    | pool_id        | 794ccc2c-d751-44fe-b57f-8894c9f5c842     |
    | project_id     | 123d51544df443e790b8e95cce52c285         |
    | serial         | 1591119166                               |
    | status         | PENDING                                  |
    | transferred_at | None                                     |
    | ttl            | 3600                                     |
    | type           | PRIMARY                                  |
    | updated_at     | None                                     |
    | version        | 1                                        |
    +----------------+------------------------------------------+

Now that we have our in-addr.arpa. zone, we add a new PTR record to the zone.

    POST /v2/zones/f5546034-b27e-4326-bf9d-c53ed879f7fa/recordsets HTTP/1.1
    Content-Type: application/json
    Accept: application/json

    {
      "name": "11.2.0.192.in-addr.arpa.",
      "type": "PTR",
      "records": [
        "example.org."
      ],
      "ttl": 3600,
      "description": "A PTR recordset"
    }

Here is the response.

    HTTP/1.1 202 Accepted
    Location: http://127.0.0.1:9001/v2/zones/f5546034-b27e-4326-bf9d-c53ed879f7fa/recordsets/ca604f72-83e6-421f-bf1c-bb4dc1df994a
    Content-Length: 573
    Content-Type: application/json; charset=UTF-8
    X-Openstack-Request-Id: req-5b7044d0-591a-445a-839f-1403b1455824
    Date: Tue, 02 Jun 2020 19:55:50 GMT
    Connection: keep-alive

    {
      "id": "ca604f72-83e6-421f-bf1c-bb4dc1df994a",
      "zone_id": "f5546034-b27e-4326-bf9d-c53ed879f7fa",
      "project_id": "123d51544df443e790b8e95cce52c285",
      "name": "11.2.0.192.in-addr.arpa.",
      "zone_name": "11.2.0.192.in-addr.arpa.",
      "type": "PTR",
      "records": [
        "example.org."
      ],
      "description": "A PTR recordset",
      "ttl": 3600,
      "status": "PENDING",
      "action": "CREATE",
      "version": 1,
      "created_at": "2020-06-02T19:55:50.000000",
      "updated_at": null,
      "links": {
        "self": "http://127.0.0.1:9001/v2/zones/f5546034-b27e-4326-bf9d-c53ed879f7fa/recordsets/ca604f72-83e6-421f-bf1c-bb4dc1df994a"
      }
    }

With the CLI:

    $ openstack recordset create --record example.org. --type PTR \
        --ttl 3600 --description "A PTR recordset" \
        11.2.0.192.in-addr.arpa. 11.2.0.192.in-addr.arpa.
    +-------------+--------------------------------------+
    | Field       | Value                                |
    +-------------+--------------------------------------+
    | action      | CREATE                               |
    | created_at  | 2020-06-02T19:55:50.000000           |
    | description | A PTR recordset                      |
    | id          | ca604f72-83e6-421f-bf1c-bb4dc1df994a |
    | name        | 11.2.0.192.in-addr.arpa.             |
    | project_id  | 123d51544df443e790b8e95cce52c285     |
    | records     | example.org.                         |
    | status      | PENDING                              |
    | ttl         | 3600                                 |
    | type        | PTR                                  |
    | updated_at  | None                                 |
    | version     | 1                                    |
    | zone_id     | f5546034-b27e-4326-bf9d-c53ed879f7fa |
    | zone_name   | 11.2.0.192.in-addr.arpa.             |
    +-------------+--------------------------------------+

We should now have a correct PTR record assigned in our nameserver that we can test.

Let’s test it out!

    $ dig @localhost -x 192.0.2.11

    ; <<>> DiG 9.9.5-3ubuntu0.1-Ubuntu <<>> @localhost -x 192.0.2.11
    ; (1 server found)
    ;; global options: +cmd
    ;; Got answer:
    ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 32832
    ;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 1
    ;; WARNING: recursion requested but not available

    ;; OPT PSEUDOSECTION:
    ; EDNS: version: 0, flags:; udp: 4096
    ;; QUESTION SECTION:
    ;11.2.0.192.in-addr.arpa.    IN      PTR

    ;; ANSWER SECTION:
    11.2.0.192.in-addr.arpa. 3600 IN     PTR     example.org.

    ;; AUTHORITY SECTION:
    11.2.0.192.in-addr.arpa. 3600 IN     NS      ns1.example.org.

    ;; Query time: 3 msec
    ;; SERVER: 127.0.0.1#53(127.0.0.1)
    ;; WHEN: Fri Feb 20 21:45:53 UTC 2015
    ;; MSG SIZE  rcvd: 98

As you can see from the answer section everything worked as expected.

### IPv6

Following the previous example we will configure fd00::2:11 to return our example.org. domain name. As reverse DNS lookups for IPv6 addresses use the special domain ip6.arpa, we need to create

    $ openstack zone create --email admin@example.org \
        --ttl 3600 --description "A ip6.arpa zone for IPv6 reverse lookups" \
        1.1.0.0.2.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.d.f.ip6.arpa.
    +----------------+---------------------------------------------------------------------------+
    | Field          | Value                                                                     |
    +----------------+---------------------------------------------------------------------------+
    | action         | CREATE                                                                    |
    | attributes     |                                                                           |
    | created_at     | 2020-06-04T13:07:36.000000                                                |
    | description    | IPv6 reverse lookup zone                                                  |
    | email          | admin@example.org                                                         |
    | id             | 9c8f30a1-6d9d-4f40-9fac-ab8abfb24fba                                      |
    | masters        |                                                                           |
    | name           | 1.1.0.0.2.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.d.f.ip6.arpa. |
    | pool_id        | 794ccc2c-d751-44fe-b57f-8894c9f5c842                                      |
    | project_id     | 123d51544df443e790b8e95cce52c285                                          |
    | serial         | 1591276055                                                                |
    | status         | PENDING                                                                   |
    | transferred_at | None                                                                      |
    | ttl            | 3600                                                                      |
    | type           | PRIMARY                                                                   |
    | updated_at     | None                                                                      |
    | version        | 1                                                                         |
    +----------------+---------------------------------------------------------------------------+

And add the PTR record

    $ openstack recordset create --record example.org. --type PTR \
        --ttl 3600 --description "A PTR recordset" \
        1.1.0.0.2.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.d.f.ip6.arpa. \
        1.1.0.0.2.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.d.f.ip6.arpa.
    +-------------+---------------------------------------------------------------------------+
    | Field       | Value                                                                     |
    +-------------+---------------------------------------------------------------------------+
    | action      | CREATE                                                                    |
    | created_at  | 2020-06-04T13:10:30.000000                                                |
    | description | A PTR recordset                                                           |
    | id          | 246c5cbb-315d-437d-a52f-bf0a0cfa91a0                                      |
    | name        | 1.1.0.0.2.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.d.f.ip6.arpa. |
    | project_id  | 123d51544df443e790b8e95cce52c285                                          |
    | records     | example.org.                                                              |
    | status      | PENDING                                                                   |
    | ttl         | 3600                                                                      |
    | type        | PTR                                                                       |
    | updated_at  | None                                                                      |
    | version     | 1                                                                         |
    | zone_id     | 9c8f30a1-6d9d-4f40-9fac-ab8abfb24fba                                      |
    | zone_name   | 1.1.0.0.2.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.d.f.ip6.arpa. |
    +-------------+---------------------------------------------------------------------------+

Now we can do a reverse lookup with

    $ dig @localhost -x fd00::2:11

    ; <<>> DiG 9.11.3-1ubuntu1.12-Ubuntu <<>> @10.5.0.32 -x fd00::2:11
    ; (1 server found)
    ;; global options: +cmd
    ;; Got answer:
    ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 50892
    ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 1

    ;; OPT PSEUDOSECTION:
    ; EDNS: version: 0, flags:; udp: 4096
    ; COOKIE: 812dd247d36b98504b6d12485ed8f44bd7ae0a902343c348 (good)
    ;; QUESTION SECTION:
    ;1.1.0.0.2.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.d.f.ip6.arpa. IN PTR

    ;; ANSWER SECTION:
    1.1.0.0.2.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.d.f.ip6.arpa. 3600 IN PTR example.org.

    ;; AUTHORITY SECTION:
    1.1.0.0.2.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.d.f.ip6.arpa. 3600 IN NS ns1.example.org.

    ;; Query time: 1 msec
    ;; SERVER: 127.0.0.1#53(127.0.0.1)
    ;; WHEN: Thu Jun 04 13:16:59 UTC 2020
    ;; MSG SIZE  rcvd: 197

### Advanced Usage

You can add many PTR records to a larger subnet by using a more broadly defined in-addr.arpa. zone. For example, if we wanted to ensure any IP in a subnet resolves to a specific domain we would add a wildcard DNS record to this zone.

    POST /v2/zones HTTP/1.1
    Accept: application/json
    Content-Type: application/json

    {
      "name": "2.0.192.in-addr.arpa.",
      "type": "PRIMARY",
      "email": "admin@example.org",
      "ttl": 3600,
      "description": "A more broadly defined in-addr.arpa. zone for reverse lookups"
    }

With the CLI:

    $ openstack zone create --email admin@example.org --ttl 3600 \
        --description "A more broadly defined in-addr.arpa. zone for reverse lookups" \
        2.0.192.in-addr.arpa.
    +----------------+---------------------------------------------------------------+
    | Field          | Value                                                         |
    +----------------+---------------------------------------------------------------+
    | action         | CREATE                                                        |
    | attributes     |                                                               |
    | created_at     | 2020-06-02T20:07:11.000000                                    |
    | description    | A more broadly defined in-addr.arpa. zone for reverse lookups |
    | email          | admin@example.org                                             |
    | id             | e9fd0ced-1d3e-43fa-b9aa-6d4b7a73988d                          |
    | masters        |                                                               |
    | name           | 2.0.192.in-addr.arpa.                                         |
    | pool_id        | 794ccc2c-d751-44fe-b57f-8894c9f5c842                          |
    | project_id     | 123d51544df443e790b8e95cce52c285                              |
    | serial         | 1591128431                                                    |
    | status         | PENDING                                                       |
    | transferred_at | None                                                          |
    | ttl            | 3600                                                          |
    | type           | PRIMARY                                                       |
    | updated_at     | None                                                          |
    | version        | 1                                                             |
    +----------------+---------------------------------------------------------------+

We then could use the corresponding domain to create a PTR record for a specific IP.

    POST /v2/zones/e9fd0ced-1d3e-43fa-b9aa-6d4b7a73988d/recordsets HTTP/1.1
    Accept: application/json
    Content-Type: application/json

    {
      "name": "3.2.0.192.in-addr.arpa.",
      "type": "PTR"
      "ttl": 3600,
      "records": [
        "cats.example.com."
      ]
    }

With the CLI:

    $ openstack recordset create --record cats.example.org. --type PTR \
        --ttl 3600 2.0.192.in-addr.arpa. 3.2.0.192.in-addr.arpa.
    +-------------+--------------------------------------+
    | Field       | Value                                |
    +-------------+--------------------------------------+
    | action      | CREATE                               |
    | created_at  | 2020-06-02T20:10:54.000000           |
    | description | None                                 |
    | id          | c843729b-7aaf-4f99-a40a-d9bf70edf271 |
    | name        | 3.2.0.192.in-addr.arpa.              |
    | project_id  | 123d51544df443e790b8e95cce52c285     |
    | records     | cats.example.org.                    |
    | status      | PENDING                              |
    | ttl         | 3600                                 |
    | type        | PTR                                  |
    | updated_at  | None                                 |
    | version     | 1                                    |
    | zone_id     | e9fd0ced-1d3e-43fa-b9aa-6d4b7a73988d |
    | zone_name   | 2.0.192.in-addr.arpa.                |
    +-------------+--------------------------------------+

Or with a wildcard DNS record:

    $ openstack recordset create --record example.org. --type PTR \
        --ttl 3600 2.0.192.in-addr.arpa. *.2.0.192.in-addr.arpa.
    +-------------+--------------------------------------+
    | Field       | Value                                |
    +-------------+--------------------------------------+
    | action      | CREATE                               |
    | created_at  | 2020-06-04T12:22:45.000000           |
    | description | None                                 |
    | id          | 4fa96619-a1f8-4409-ba5f-fa904db4c97c |
    | name        | *.2.0.192.in-addr.arpa.              |
    | project_id  | 123d51544df443e790b8e95cce52c285     |
    | records     | example.org.                         |
    | status      | PENDING                              |
    | ttl         | 3600                                 |
    | type        | PTR                                  |
    | updated_at  | None                                 |
    | version     | 1                                    |
    | zone_id     | e9fd0ced-1d3e-43fa-b9aa-6d4b7a73988d |
    | zone_name   | 2.0.192.in-addr.arpa.                |
    +-------------+--------------------------------------+

When we do our reverse look, we should see cats.example.com.

    $ dig @localhost -x 192.0.2.3 +short
    cats.example.com.

When we query any other IP address in 192.0.2.0/24 we get

    $ dig @10.5.0.32 -x 192.0.2.10 +short
    example.org.

Success!

Note

In BIND9, when creating a new PTR we could skip the zone name. For example, if the zone is 2.0.192.in-addr.arpa., using 12 for the record name ends up as 12.2.0.192.in-addr.arpa.. In Designate, the name of a record MUST be a complete host name.

## Classless IN-Addr.ARPA Delegation

You may want to delegate blocks of IP addresses to projects that do not align to subnet boundries. For example, if you wanted to give project “A” three IP addresses. To allow project “A” to manage DNS records for those three addresses, without delegating a whole subnet zone to project “A”, you can use classless IN-ADDR.ARPA delegation as described in RFC 2317.

Note

As discussed in section 4 of RFC 2317, the examples in the RFC use ‘/’ in the delegated zones but ‘-’ is recommended. Designate will not allow you to use ‘/’ in zone names. You will need to use the recommended ‘-’ instead.

In this example, we will delegate a PTR zone for three IP addresses, from the 192.0.2.0/24 subnet, to the Demo project ‘9284a20339184a9bb299386c380211c7’.

Note

Unless noted in the examples, the commands are using a credential with an admin role. This is not necessary, but is a typical use case.

First, the full subnet in-addr.arpa zone will need to be created:

    $ openstack zone create --email me@example.com 2.0.192.in-addr.arpa.
    +----------------+--------------------------------------+
    | Field          | Value                                |
    +----------------+--------------------------------------+
    | action         | CREATE                               |
    | attributes     |                                      |
    | created_at     | 2022-09-09T20:05:41.000000           |
    | description    | None                                 |
    | email          | me@example.com                       |
    | id             | bbdf0e8f-8d73-4659-ae62-f59e95a31cd7 |
    | masters        |                                      |
    | name           | 2.0.192.in-addr.arpa.                |
    | pool_id        | 794ccc2c-d751-44fe-b57f-8894c9f5c842 |
    | project_id     | cc5ab848dbe7462e9c7603d54a9af90f     |
    | serial         | 1662753940                           |
    | status         | PENDING                              |
    | transferred_at | None                                 |
    | ttl            | 3600                                 |
    | type           | PRIMARY                              |
    | updated_at     | None                                 |
    | version        | 1                                    |
    +----------------+--------------------------------------+

Next we will create the delegated zone:

    $ openstack zone create --email me@example.com 1-3.2.0.192.in-addr.arpa.
    +----------------+--------------------------------------+
    | Field          | Value                                |
    +----------------+--------------------------------------+
    | action         | CREATE                               |
    | attributes     |                                      |
    | created_at     | 2022-09-09T20:06:59.000000           |
    | description    | None                                 |
    | email          | me@example.com                       |
    | id             | 2d353ed7-cb7f-4ff7-9c1e-54481304f4cb |
    | masters        |                                      |
    | name           | 1-3.2.0.192.in-addr.arpa.            |
    | pool_id        | 794ccc2c-d751-44fe-b57f-8894c9f5c842 |
    | project_id     | cc5ab848dbe7462e9c7603d54a9af90f     |
    | serial         | 1662754018                           |
    | status         | PENDING                              |
    | transferred_at | None                                 |
    | ttl            | 3600                                 |
    | type           | PRIMARY                              |
    | updated_at     | None                                 |
    | version        | 1                                    |
    +----------------+--------------------------------------+

Now we can share the delegated zone with the Demo project:

    $ openstack zone share create 1-3.2.0.192.in-addr.arpa. 9284a20339184a9bb299386c380211c7
    +-------------------+--------------------------------------+
    | Field             | Value                                |
    +-------------------+--------------------------------------+
    | created_at        | 2022-09-09T20:07:20.000000           |
    | id                | 7859ca43-bcee-4fd1-aa2d-efda17b75198 |
    | project_id        | cc5ab848dbe7462e9c7603d54a9af90f     |
    | target_project_id | 9284a20339184a9bb299386c380211c7     |
    | updated_at        | None                                 |
    | zone_id           | 2d353ed7-cb7f-4ff7-9c1e-54481304f4cb |
    +-------------------+--------------------------------------+

Once we have the zones created and shared, we can now add the CNAME records to the full subnet zone that point to the delegated zone records. This will need to be repeated for each IP address being delegated. This example creates the first CNAME record for the 192.0.2.1 IP address.

    $ openstack recordset create --record 1.1-3.2.0.192.in-addr.arpa. --type CNAME 2.0.192.in-addr.arpa. 1.2.0.192.in-addr.arpa.
    +-------------+--------------------------------------+
    | Field       | Value                                |
    +-------------+--------------------------------------+
    | action      | CREATE                               |
    | created_at  | 2022-09-09T20:09:16.000000           |
    | description | None                                 |
    | id          | 482bd367-9815-4d86-a93d-734bbc92499a |
    | name        | 1.2.0.192.in-addr.arpa.              |
    | project_id  | cc5ab848dbe7462e9c7603d54a9af90f     |
    | records     | 1.1-3.2.0.192.in-addr.arpa.          |
    | status      | PENDING                              |
    | ttl         | None                                 |
    | type        | CNAME                                |
    | updated_at  | None                                 |
    | version     | 1                                    |
    | zone_id     | bbdf0e8f-8d73-4659-ae62-f59e95a31cd7 |
    | zone_name   | 2.0.192.in-addr.arpa.                |
    +-------------+--------------------------------------+

Finally, members of the Demo project can now create the PTR records for the delegates IP addresses. In this example the administrator will create the first record on behalf of the Demo project.

    $ openstack recordset create --sudo-project-id 9284a20339184a9bb299386c380211c7 --record www.example.com. --type PTR 1-3.2.0.192.in-addr.arpa. 1.1-3.2.0.192.in-addr.arpa.
    +-------------+--------------------------------------+
    | Field       | Value                                |
    +-------------+--------------------------------------+
    | action      | CREATE                               |
    | created_at  | 2022-09-09T20:08:17.000000           |
    | description | None                                 |
    | id          | cea3f3ce-687b-422c-a378-bdcfe382a159 |
    | name        | 1.1-3.2.0.192.in-addr.arpa.          |
    | project_id  | 9284a20339184a9bb299386c380211c7     |
    | records     | www.example.com.                     |
    | status      | PENDING                              |
    | ttl         | None                                 |
    | type        | PTR                                  |
    | updated_at  | None                                 |
    | version     | 1                                    |
    | zone_id     | 2d353ed7-cb7f-4ff7-9c1e-54481304f4cb |
    | zone_name   | 1-3.2.0.192.in-addr.arpa.            |
    +-------------+--------------------------------------+

We can now use dig to query a recursive resolver to verify the delegation:

    $ dig -x 192.0.2.1 @198.51.100.5

    ; <<>> DiG 9.16.32-RH <<>> -x 192.0.2.1 @198.51.100.5
    ;; global options: +cmd
    ;; Got answer:
    ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 16209
    ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1

    ;; OPT PSEUDOSECTION:
    ; EDNS: version: 0, flags:; udp: 4096
    ; COOKIE: a415d9b43dcef11c01000000631ba068973cbfbf5b765032 (good)
    ;; QUESTION SECTION:
    ;1.2.0.192.in-addr.arpa.            IN      PTR

    ;; ANSWER SECTION:
    1.2.0.192.in-addr.arpa.     3600    IN      CNAME   1.1-3.2.0.192.in-addr.arpa.
    1.1-3.2.0.192.in-addr.arpa. 3600 IN PTR     www.example.com.

    ;; Query time: 0 msec
    ;; SERVER: 198.51.100.5#53(198.51.100.5)
    ;; WHEN: Fri Sep 09 13:22:00 PDT 2022
    ;; MSG SIZE  rcvd: 149

Note

Your resolver or DNS server settings (such as allow recursion and/or minimal responses) may cause dig to only display the CNAME and not resolve the PTR record in the same request.

this page last updated: 2026-08-19 02:25:39

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