Created PTR records are ignored by CoreDNS

[NHellFire]

What happened:

Records are created in etcd:

$ kubectl logs deploy/external-dns
time="2026-06-01T18:02:36Z" level=info msg="Generating new prefix: (41d1e77d)"
time="2026-06-01T18:02:36Z" level=info msg="Delete key /skydns/arpa/in-addr/172/26/0/2/cluster1"
time="2026-06-01T18:02:36Z" level=info msg="Add/set key /skydns/arpa/in-addr/172/26/0/2/41d1e77d to Host=coredns-etcd-worker, Text=, TTL=0"
time="2026-06-01T18:02:36Z" level=info msg="Generating new prefix: (489d3005)"
time="2026-06-01T18:02:36Z" level=info msg="Delete key /skydns/arpa/in-addr/172/26/0/3/cluster1"
time="2026-06-01T18:02:36Z" level=info msg="Add/set key /skydns/arpa/in-addr/172/26/0/3/489d3005 to Host=coredns-etcd-control-plane, Text=, TTL=0"

But not returned by CoreDNS:

$ kubectl run --rm -it dnsutils --image=infoblox/dnstools --restart=Never
All commands and output from this session will be recorded in container logs, including credentials and sensitive information passed through the command prompt.
If you don't see a command prompt, try pressing enter.
dnstools# host 172.26.0.2 coredns.default.svc.cluster.local
Using domain server:
Name: coredns.default.svc.cluster.local
Address: 10.96.71.74#53
Aliases:

Host 2.0.26.172.in-addr.arpa. not found: 3(NXDOMAIN)

What you expected to happen:

The record to resolve.

How to reproduce it (as minimally and precisely as possible):

1. Create cluster

$ curl -L https://github.com/kubernetes-sigs/external-dns/raw/refs/tags/v0.21.0/docs/snippets/tutorials/coredns/kind.yaml | kind create cluster --config -

2. Deploy etcd

$ kubectl apply -f https://github.com/kubernetes-sigs/external-dns/raw/refs/tags/v0.21.0/docs/snippets/tutorials/coredns/etcd.yaml
$ kubectl rollout status statefulset etcd

3. Deploy CoreDNS

$ helm repo add coredns https://coredns.github.io/helm
$ helm repo update
$ helm upgrade --install coredns coredns/coredns \
  -f https://github.com/user-attachments/files/28475732/values-coredns.yaml \
  -n default

4. Deploy external-dns

$ helm repo add external-dns https://kubernetes-sigs.github.io/external-dns/
$ helm repo update
$ helm upgrade --install external-dns external-dns/external-dns \
  -f https://github.com/user-attachments/files/28475733/values-external-dns.yaml \
  -n default

Anything else we need to know?:

The CoreDNS docs only specify keys like /skydns/arpa/in-addr/10/0/0/127, looks like the etcd backend doesn't support multiple PTR records.

If I duplicate the entry without the unique key:

$ kubectl exec -it etcd-0 -- etcdctl put /skydns/arpa/in-addr/172/26/0/2 '{"host":"coredns-etcd-worker","targetstrip":1}'
OK

And test again, I get the expected result:

dnstools# host 172.26.0.2 coredns.default.svc.cluster.local
Using domain server:
Name: coredns.default.svc.cluster.local
Address: 10.96.71.74#53
Aliases:

2.0.26.172.in-addr.arpa domain name pointer coredns-etcd-worker.

Environment:

• External-DNS version (use external-dns --version): v20260406-v0.21.0
• DNS provider: coredns
• Others:

Checklist

• I have searched existing issues and tried to find a fix myself
• I am using the latest release,
  or have checked the staging image to confirm the bug is still reproducible
• I have provided the actual process flags (not Helm values)
• I have provided kubectl get <resource> -o yaml output including status
• I have provided full external-dns debug logs
• I have described what DNS records exist and what I expected

values-external-dns.yaml
values-coredns.yaml

[ivankatliarchuk]

It's unsafe to download files from random estranges on the internet.

I don't think there is a support for PTR records. From the first look only handles A and CNAME

[NHellFire]

Those values.xml files are attached to the issue, and modified from docs/snippets/tutorials/coredns to enable PTR records like so:

diff --git a/docs/snippets/tutorials/coredns/values-coredns.yaml b/docs/snippets/tutorials/coredns/values-coredns.yaml
index b03f8ea8..e6903ac9 100644
--- a/docs/snippets/tutorials/coredns/values-coredns.yaml
+++ b/docs/snippets/tutorials/coredns/values-coredns.yaml
@@ -28,12 +28,11 @@ servers:
           fallthrough in-addr.arpa ip6.arpa
           ttl 30
       - name: etcd
-        parameters: "example.org"
+        parameters: "example.org in-addr.arpa"
         configBlock: |
           stubzones
           path /skydns
           endpoint http://etcd.default.svc.cluster.local:2379
-          fallthrough
       - name: log # <── log each DNS query
       - name: forward
         parameters: ". /etc/resolv.conf"
diff --git a/docs/snippets/tutorials/coredns/values-extdns-coredns.yaml b/docs/snippets/tutorials/coredns/values-extdns-coredns.yaml
index f0543a8f..18b3295c 100644
--- a/docs/snippets/tutorials/coredns/values-extdns-coredns.yaml
+++ b/docs/snippets/tutorials/coredns/values-extdns-coredns.yaml
@@ -9,15 +9,15 @@ env:


 txtOwnerId: cluster1
-# Filter resources queried for endpoints by annotation, using label selector semantics
-annotationFilter: cluster-name=cluster1

-domainFilters:
-  - example.org
+extraArgs: [ --create-ptr ]
+managedRecordTypes: [ A, AAAA, CNAME, PTR ]

 # Sources define what ExternalDNS will use to discover endpoints
 sources:
   - service
+  - node
+  - pod

 # Policy options
 policy: sync

[ivankatliarchuk]

What I mean, PTR records not supported yet by coredns

/kind feature

[NHellFire]

#6232 made PTR records available to all providers. The CoreDNS provider and both CoreDNS support PTR records, however CoreDNS only supports a single PTR record, with no unique suffix.