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1Clear out junk files and repair common Windows errors2Scan for outdated or missing drivers - takes under a minute3Repair Windows errors before they cause bigger problemsUse an A record when your host gives you an IPv4 address. Use a CNAME when it gives you another hostname. If the host supplies an IPv6 address, add an AAAA record. Then configure the web host and TLS certificate for that same name; DNS only directs requests and does not create the site.
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The short decision: match the record to the destination you were given
A subdomain such as blog.example.com is normally added to the authoritative DNS zone for example.com. The record type depends on what the service you are connecting to supplies:
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- IPv4 address: create an A record.
- IPv6 address: create an AAAA record.
- Hostname: create a CNAME record pointing to that fully qualified name.
Do not put an IP address in a CNAME field. A CNAME target is a DNS name, not an address. Conversely, do not turn a provider’s hostname into an A record unless the provider explicitly gives you an IP address and says it is stable enough for that use. Hosted platforms often change the addresses behind their hostname; the alias lets their DNS continue to direct your traffic without requiring you to edit your zone.
A record versus CNAME: what changes in practice?
| Question | A record | CNAME record |
|---|---|---|
| Destination | One IPv4 address | Another DNS hostname |
| Typical use | A server or load balancer whose IPv4 address you control or were assigned | A SaaS, CDN, or hosted service that gives you an endpoint name |
| When the endpoint changes | You must update the address in your zone | The target provider can change its own addresses behind the hostname |
| IPv6 | Use a separate AAAA record for an IPv6 address | The target name can resolve to IPv4, IPv6, or both |
| Zone-apex compatibility | Can be used at the apex, subject to your provider’s normal rules | A standard CNAME cannot be used at the apex |
| Other records at the same name | Can coexist with other record types where DNS permits | Cannot share its name with MX, TXT, A, AAAA, or other data records |
| Operational control | Direct control over the address returned | Delegates endpoint selection to the target hostname’s operator |
An A record maps a name directly to an IPv4 address. A CNAME creates an alias: a resolver follows the alias and then looks up the target name. The choice is not a matter of which record is “faster”; it is determined by the destination format and by whether the service expects you to use an alias.
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Before adding anything, find the authoritative DNS provider
Changing records at your domain registrar will not help if another company hosts the domain’s authoritative zone. Look at the domain’s nameservers, then open the DNS dashboard belonging to the provider named there. That is where the record must be created.
You can inspect the delegation from a terminal with:
dig NS example.comThe nameservers returned for the parent domain identify the authoritative service. Some registrars also offer DNS hosting, while others only sell the domain and point it to a separate DNS provider. If you edit the wrong dashboard, the record may appear to save successfully but never reach public resolvers.
How to add blog.example.com, step by step
- Get the provider’s required destination. Confirm whether the service supplied an IPv4 address, an IPv6 address, or a hostname. Copy the value exactly. For a CNAME, preserve the complete hostname as supplied.
- Open the authoritative DNS zone. Choose the domain that contains
example.com, then select the dashboard action usually labelled Add record, Create record, or similar. - Enter only the label in the Name field. For
blog.example.com, many dashboards expectblog, not the complete domain. Some interfaces accept the full name and remove the zone automatically; follow the field’s displayed example so you do not accidentally createblog.example.com.example.com. - Select the type. Choose A for IPv4, AAAA for IPv6, or CNAME for a hostname.
- Enter the value. Put the numeric address in an A or AAAA record. Put the provider’s DNS name in a CNAME record. Never put
https://, a path such as/login, or a port number in a DNS value. - Set TTL and any proxy option. Keep the provider’s recommended default unless you have a migration reason to change it. If the dashboard offers DNS-only and proxied modes, record which mode you selected because it affects the answer clients observe.
- Save the record. Check the resulting row for spelling, type, and value before leaving the page.
- Configure the web service. Add
blog.example.comto the hosted application’s custom-domain, site, virtual-host, or domain settings. Request or enable a certificate for the hostname if the platform does not issue one automatically. - Verify from DNS and HTTP. Query the authoritative server and a public resolver, then load the hostname over HTTPS and confirm that the expected site and certificate are returned.
Cloudflare’s documented procedure expresses the core entry similarly: choose A, use the subdomain (such as blog) as the record name, and enter the IPv4 address in the address field. Interfaces differ, but the DNS data does not.
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DNS pointing and website configuration are separate
A successful DNS lookup does not prove that a website is ready. The web server must recognize the Host name (or the HTTPS server-name indication), route it to the correct application, and present a certificate covering that hostname. If you add only the DNS record, visitors may see a provider’s default page, a 404 response, a connection error, or a certificate warning.
Complete both sides:
- Add the subdomain to the hosting platform or web server’s list of accepted domains.
- Issue, upload, or enable TLS for the exact hostname. A certificate for
example.comalone does not automatically coverblog.example.com. - Set redirects and application URLs if the software treats the subdomain as a separate origin.
- Check any email, API, cookie, or content-security settings that intentionally restrict allowed hostnames.
When a CNAME is the right choice
Hosted platforms and changing endpoints
Use a CNAME when a service instructs you to point a name such as blog.example.com to customer.provider.example. The target name is the provider’s stable interface; its operator can move traffic among addresses without asking every customer to edit DNS. This is the usual pattern for hosted sites, application platforms, and many content-delivery services.
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Do not mix a CNAME with other data at the same name
DNS treats a CNAME as an alias for the entire name. Therefore, blog.example.com cannot simultaneously have a CNAME and an A, AAAA, MX, TXT, or other record at that exact name. Put mail-related records on a different hostname, and remove an old address record before creating the CNAME if the provider requires an exclusive alias.
Why the root domain cannot normally use a CNAME
The zone apex is the bare domain, example.com. It is also where the zone’s authoritative NS and SOA records live. The DNS protocol does not allow a conventional CNAME at that top node, a restriction documented by Amazon Web Services for Route 53. A name such as www.example.com or blog.example.com is below the apex and can normally use a CNAME.
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If a service asks you to point the apex to a hostname, use the feature your DNS provider supplies for that purpose:
- Route 53 alias records can point the apex to selected AWS resources.
- Google Cloud DNS ALIAS provides CNAME-like apex behavior in that provider’s implementation.
- Other providers may call the feature ALIAS, ANAME, or CNAME flattening.
These are provider features, not interchangeable new DNS record types available everywhere. If your provider has none of them, use an A/AAAA address supplied for the apex or place the CNAME on www and redirect the bare domain through a supported web service.
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An AAAA record is the IPv6 counterpart to an A record. If your host supplies both address families, you may publish both at the same hostname. Clients that support IPv6 can use the AAAA answer, while others use A. Do not place an IPv6 address in an A record; the record type must match the address family.
Ask the provider whether the IPv6 address is dedicated and stable. If it is temporary or dynamically assigned, follow the provider’s hostname-based method instead of hard-coding it.
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Keeping records in the parent zone or delegating the subdomain
Most organizations keep blog.example.com as an ordinary record in the example.com hosted zone. That is simplest when one team manages the whole domain.
For operational separation, create a separate hosted zone for sub.example.com. Add NS records for that child zone in the parent zone. From then on, the delegated nameservers manage every name below sub.example.com. AWS documents both models: records can stay in the parent hosted zone, or a separately hosted child zone can be delegated with NS records.
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Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.TTL, caching, and proxy modes
TTL is the time recursive resolvers may cache an answer. A lower TTL helps during a planned migration because resolvers are allowed to refresh sooner, but it causes more DNS lookups. A higher TTL reduces repeated queries and can improve cache efficiency, but old answers may remain visible longer after a change.
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Lower the TTL before a migration, make the change, verify the new destination, and restore a normal value afterward if your operating policy calls for it. TTL is not a guarantee that every client changes at exactly that second: recursive resolvers, application caches, and provider behavior can affect observation time.
Some DNS providers offer a proxy mode in which traffic is routed through their network rather than answered as DNS-only. Proxying can change the address clients see and may apply a provider-controlled or default TTL. Document the selected mode, especially when troubleshooting or comparing an authoritative answer with a public lookup.
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Verify the record instead of guessing
Check the authoritative response first, then ask a public resolver. Replace the example names with your own values:
dig blog.example.com A
dig blog.example.com AAAA
dig blog.example.com CNAME
dig @authoritative-nameserver.example blog.example.com- An A query should return the expected IPv4 address when an A record is configured.
- An AAAA query should return the expected IPv6 address when one is configured.
- A CNAME query should show the target hostname. A resolver may then return the target’s A or AAAA address in the final answer.
- The authoritative query tells you whether the zone is correct; a normal query tells you what a recursive resolver currently has cached.
After DNS is correct, test the service itself:
curl -I https://blog.example.comConfirm that the status, redirect chain, response headers, page content, and certificate belong to the intended application. A DNS answer that points somewhere else, or a certificate issued for a different name, indicates a hosting configuration problem rather than a missing DNS record.
Troubleshooting by symptom
“NXDOMAIN” or no answer
- Check that you edited the authoritative provider, not only the registrar.
- Confirm the label and zone. A dashboard that automatically appends the zone can turn a full name into a duplicated name.
- Check whether the record was saved and whether the queried nameserver is authoritative for the domain.
- Allow for the previous TTL while recursive caches expire.
“SERVFAIL”
- Inspect the authoritative response for a delegation or DNSSEC problem.
- For a CNAME, verify that the target hostname exists and is spelled exactly as supplied.
- If you delegated a child zone, confirm that the parent NS records and child nameservers agree.
The lookup returns an address, but the wrong site loads
- Check the web server’s virtual-host or custom-domain mapping.
- Check whether a proxy is intentionally returning an intermediary address.
- Remove conflicting A, AAAA, or CNAME data at the same name and wait for caches to refresh.
HTTPS shows a certificate warning
- Ensure the certificate includes the exact subdomain, not just the parent domain.
- Complete the hosting provider’s domain-verification step and wait for certificate issuance.
- Check that the server selected the correct certificate for the hostname during TLS negotiation.
The provider rejects the record at the root domain
You are probably trying to create a conventional CNAME at the zone apex. Use the provider’s alias, ALIAS, ANAME, or CNAME-flattening feature, or follow the provider’s documented A/AAAA alternative. Do not work around the restriction by adding an invalid CNAME beside the apex’s required records.
A safe migration pattern
For a move from one host to another, first lower the existing record’s TTL while the old service is still working. Prepare the new site’s hostname and certificate, then change the A, AAAA, or CNAME value. Query the authoritative server, test through more than one public resolver, and verify the application over HTTPS. Keep the old service available until normal resolver caches have had time to expire and traffic confirms the cutover. Restore the normal TTL after the migration is stable.
Quick Recap
Practical checklist
- Identify the authoritative DNS provider.
- Decide whether the destination is IPv4, IPv6, or a hostname.
- Use A for IPv4, AAAA for IPv6, and CNAME for a hostname.
- Use the subdomain label in the Name field as required by the dashboard.
- Never put a URL, path, or port in a DNS value.
- Do not combine a CNAME with other record types at the same name.
- Use an alias-style provider feature for an apex hostname instead of a standard CNAME.
- Configure the web host and TLS certificate separately.
- Account for TTL and proxy behavior during changes.
- Verify authoritative DNS, public DNS, HTTP response, and certificate.
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