Add a provider's DNS verification record and remove it only when appropriate
Providers commonly ask you to add a TXT or CNAME record to demonstrate control of a domain....
Check DNS over TCP when large or signed answers fail
DNS needs TCP as well as UDP for reliable operation. Larger answers, including some signed...
Check forward-confirmed reverse DNS for a mail server address
Forward-confirmed reverse DNS means that a sending IP resolves through PTR to a hostname and...
Choose an address that public DNS users can actually reach
An A or AAAA record can be syntactically valid while pointing to an address that public...
Coordinate a DNSSEC key rollover with the registrar's DS update
A DNSSEC key rollover replaces signing keys while allowing cached trust information to remain...
Delegate a subdomain to another authoritative DNS provider
Delegating a subdomain lets another DNS service manage a branch such as shop.example.com while...
Delegate certificate DNS validation without exposing the main zone credential
DNS-01 certificate validation proves control through a TXT record at an _acme-challenge name. A...
Diagnose DNSSEC validation failures that appear as SERVFAIL
DNSSEC validation can turn an otherwise visible DNS answer into SERVFAIL when the chain of...
Diagnose a listed nameserver that does not serve the delegated zone
A delegation is lame when a nameserver listed for a zone cannot provide the expected...
Diagnose a website that fails only over IPv6 after an AAAA change
An incorrect AAAA record can send IPv6-capable visitors to an unavailable server while IPv4...
Diagnose different internal and public DNS answers for one hostname
Split DNS intentionally gives different answers to different networks or clients. An internal...
Find a CNAME loop or an alias chain that points to an absent target
A CNAME follows a hostname to another hostname. A chain that returns to an earlier name, or...
Fix a private nameserver delegation that depends on missing glue
A nameserver such as ns1.example.com can host example.com only when resolvers can find its...
Fix an MX target that cannot deliver mail even though the domain resolves
An MX record identifies a mail-exchange hostname, not an IP address or website URL. The target...
Investigate DNS answers that fail on one network but work elsewhere
A DNS answer can fail on one network when a large UDP response is fragmented or filtered while...
Keep a portable DNS inventory when the provider has no export button
A portable DNS inventory lets you review changes and prepare a migration even when the current...
Make www and the root domain reach the same website consistently
The root domain and its www hostname are separate DNS names. They can reach the same site, but...
Move a branded nameserver to a new IP without breaking its customer zones
Moving a branded nameserver to a new IP can affect every customer zone that delegates to its...
Move a signed domain to another DNS provider without a stale DS record
Moving authoritative DNS for a signed domain requires a DNSSEC transition as well as a...
Point an apex domain at a hosted service without an invalid CNAME
The apex is the domain itself, such as example.com. An ordinary CNAME cannot coexist there with...
Prepare a reversible DNS change with an exact before-and-after record list
A reversible DNS change starts with an exact record inventory and a working destination that...
Publish a child zone's DS record in the correct parent zone
A DS record belongs in the parent of the signed zone it authenticates. For a registered domain,...
Publish a long TXT value without adding unintended quotes or spaces
A DNS TXT record can contain more than one character-string. Long DKIM keys and other provider...
Publish a null MX for a domain that intentionally receives no email
A null MX explicitly declares that a domain does not accept email. It is useful for a domain...
Publish an SRV record using the service's priority, weight and port
An SRV record tells compatible clients which host and port provide a named service. Its service...
Review unexplained DNS changes and recover control of the authorised account
An unexplained DNS change can come from an authorised deployment, an automation error or...
Understand HTTPS and SVCB records before adding them to a hosting zone
HTTPS and SVCB records can advertise service endpoints and connection parameters to compatible...
Understand the limits of publishing several A or AAAA records
Publishing several A or AAAA records can make a hostname resolve to several server addresses....
Understand when a wildcard DNS record does and does not apply
A wildcard DNS record can supply an answer for names that do not have a more specific place in...
Use CAA records to authorise the certificate authorities your services need
CAA records let a domain operator express which certificate authorities may issue certificates...
Why changing DNS alone does not create a working domain parking page
DNS can point a domain to a server, but it cannot generate the page shown to visitors. A...
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