// Module included in the following assemblies:
// * networking/understanding-external-dns-operator.adoc

:_mod-docs-content-type: REFERENCE
[id="nw-external-dns-operator-domain-limitations_{context}"]
= External DNS Operator domain name limitations

[role="_abstract"]
To prevent configuration errors when deploying the `ExternalDNS` resource, review the domain name limitations enforced by the External DNS Operator. Understanding these constraints ensures that your requested hostnames and domains are compatible with your underlying DNS provider.

The External DNS Operator uses the TXT registry that adds the prefix for TXT records. This reduces the maximum length of the domain name for TXT records. A DNS record cannot be present without a corresponding TXT record, so the domain name of the DNS record must follow the same limit as the TXT records. For example, a DNS record of `<domain_name_from_source>` results in a TXT record of `external-dns-<record_type>-<domain_name_from_source>`.

The domain name of the DNS records generated by the External DNS Operator has the following limitations:

[cols="3,2",options="header"]
|===
|Record type |Number of characters

|CNAME
|44

|Wildcard CNAME records on AzureDNS
|42

|A
|48

|Wildcard A records on AzureDNS
|46

|===

The following error shows in the External DNS Operator logs if the generated domain name exceeds any of the domain name limitations:

[source,terminal]
----
time="2022-09-02T08:53:57Z" level=error msg="Failure in zone test.example.io. [Id: /hostedzone/Z06988883Q0H0RL6UMXXX]"
time="2022-09-02T08:53:57Z" level=error msg="InvalidChangeBatch: [FATAL problem: DomainLabelTooLong (Domain label is too long) encountered with 'external-dns-a-hello-openshift-aaaaaaaaaa-bbbbbbbbbb-ccccccc']\n\tstatus code: 400, request id: e54dfd5a-06c6-47b0-bcb9-a4f7c3a4e0c6"
----
