Zero‑Downtime DNSSEC: The Friendly Guide to KSK/ZSK Rollover and DS Updates Without Breaking the Internet

So there I was, a Thursday night deployment window that smelled suspiciously like a Friday 2 a.m. outage waiting to happen. We had a big DNS provider migration lined up, and the zone was DNSSEC‑signed. I’ve learned the hard way that if you mess up DS records or rush a key rollover, resolvers won’t just shrug—they’ll throw SERVFAILs like confetti. And your perfectly healthy servers will look down. That night, we took the calm path: double‑signing, double‑DS, patient TTL waits, and a few extra checks. The site never blinked. That’s when it really clicked for me that DNSSEC rollovers aren’t magic—they’re choreography.

If you’ve ever thought, “I’ll just swap the key and update the DS right after,” I get it. It feels like it should be that easy. But validators cache, parents have their own TTLs, and timing matters. In this post, I’ll walk you through the mental model I use for DNSSEC key rotation—both ZSK and KSK—plus DS updates that don’t break trust. We’ll talk about the zero‑downtime sequence, common gotchas, the friendly way to test, and how to automate so this becomes a non‑event. Along the way, I’ll share a few “ask me how I know” moments, and some practical habits that have kept my Fridays free.

First, What We’re Actually Rotating (and Why It Breaks So Easily)

Here’s the thing: DNSSEC isn’t just a signature on a zone. It’s a chain of trust. At your zone, you publish a DNSKEY set that includes two jobs: the ZSK signs your zone’s records, and the KSK signs the DNSKEY set itself. At the parent (your TLD), you publish a DS record that points to your KSK. Validators walk this chain—root to TLD’s DS to your DNSKEY—before they believe anything about your domain. Break any link, and even honest answers become “bogus.”

Rotating your ZSK affects signatures the world is actively validating for your records. Rotating your KSK affects the bridge between your zone and the parent DS. And DS updates are where things get spicy, because you don’t control the parent’s TTL the way you control your own. That’s why people get burned: they remove a DS too early, or publish one too late, or both keys aren’t visible everywhere yet. Meanwhile, resolvers are caching what they saw five minutes ago and may keep believing that version for a while.

So the secret is overlap. Like easing onto a highway, you don’t jump lanes—you blend. With ZSKs, you double‑sign. With KSKs, you double‑DS. You give validators two compatible paths so they never have to guess. If both paths are valid for a safe window, there’s no outage. If you’re thinking this sounds a lot like serving dual TLS certificates for compatibility, it is. The same spirit of “make both paths work for a while” applies. If you’ve seen how dual ECDSA + RSA on web servers keeps old clients happy, you’ll get why this approach feels so calm. For a web TLS perspective, I’ve written about serving dual ECDSA + RSA certificates on Nginx and Apache—the vibe is very similar.

The Zero‑Downtime Mindset: TTLs, Caches, and Overlap Windows

Let’s talk timing without getting lost in acronyms. Picture three clocks running at once. First is the DNSKEY TTL in your zone—the time resolvers can cache your key set. Second is the RRSIG validity window—how long the signatures your signer creates stay valid. Third is the DS TTL at the parent—how long resolvers cache that pointer from the TLD to your KSK. You can set the first two. The third is out of your hands.

When you rotate keys cleanly, your job is to make sure validators can walk the chain at any moment. The safe strategy is to pre‑publish what they’ll need, wait for caches, and only then remove the old pieces. With ZSK, you publish the new key and sign with both old and new for a window. With KSK, you publish the new KSK in your DNSKEY set, then add a DS for it at the parent, keeping the old DS in place too. That’s the overlap. Only after caches have had time to see both do you remove the old path.

One more mental model that helps: imagine validators across the world don’t check in at the same time. Some saw your zone 30 seconds ago. Others haven’t looked in hours. So if you cut one path too early, you’re betting every validator has a consistent view. They don’t. That’s why calm DNS work is about patience and guarded transitions. If you’re planning a bigger DNS rearrangement—like moving hosting or changing your apex strategy—the same calm rules apply. If you’ve ever wondered how to deal with apex records in the real world, you might enjoy my take on CNAME at the apex and ANAME/ALIAS. Different topic, same style of gentle, no‑drama migrations.

Rolling Your ZSK: The Double‑Sign Dance

I like starting with ZSK rollover because it’s the most forgiving when done properly. Think of it like swapping out a pen mid‑paragraph while still writing legibly. The approach I prefer is the pre‑publish and double‑sign method:

First, generate your new ZSK and publish it in the DNSKEY set alongside the old one. Don’t stop using the old key yet. Keep signing your zone with both. That means your records will carry two sets of signatures for a while, one from each ZSK. Validators who cached the old DNSKEY set still accept the old signatures, and validators who fetch the new DNSKEY set can verify the new signatures. No matter which view they have, they can validate.

Next, you wait. Not for days—just long enough to cover your DNSKEY TTL and give resolvers time to see the new key and the new signatures. In my experience, I like a window that makes me embarrassingly certain even sleepy caches have caught up. Then, flip your signer to stop generating signatures with the old ZSK. Keep the old key published in DNSKEY for a bit longer, though. That way, old signatures still validate while they age out. Finally, once you’re confident the old signatures have expired and caches have moved on, remove the old ZSK from the DNSKEY set.

A few seasoned tips from the field: if you use a signer that manages rollovers (BIND inline‑signing, Knot, PowerDNS with a key manager), check the actual signature validity windows. It’s easy to worry about DNSKEY TTLs and forget that signatures you baked this morning might be valid for days. That’s fine—just leave the old ZSK published until you’re sure nothing out there relies on those signatures. Also, keep an eye on monitoring. If you track RRSIG expiration and DNSKEY changes, you can watch the wave roll through and sleep better.

Every time I do this, I think back to an early client project where we rushed the remove step. We pulled the old ZSK from DNSKEY too quickly while some records were still signed by it in caches. Cue intermittent validation failures in regions we didn’t test. That was the day I tattooed “sign with both, publish both, remove last” on my brain.

Rolling Your KSK and Updating DS: The Double‑DS Bridge

KSK rotations get the headlines because the DS at the parent is the lifeline between your zone and the world. Get the sequence right, and it’s a non‑event. Get it wrong, and you’ve manufactured instant distrust. The safest path is the double‑DS approach.

Step one is familiar: generate the new KSK and publish it in your DNSKEY set alongside the current one. Do nothing at the parent yet. You’re pre‑publishing the key that will soon be trusted by the DS. Give this a little time for caches to pick up the new DNSKEY set.

Step two: add a DS record at the parent that points to the new KSK, while keeping the old DS in place. Now validators have two valid bridges from the TLD to your zone’s DNSKEY: old DS to old KSK, new DS to new KSK. That’s what we want. This is also where patience pays off, because the DS is cached on its own schedule outside your control. Let it bake. If your TLD supports CDS/CDNSKEY automation, this is even smoother—the parent can pick up your new KSK on its own and publish the DS when it sees it. I’ll come back to CDS in a moment.

Step three: now that both DS entries are out there and resolvers are happily validating via either path, it’s time to remove the old DS at the parent. Validators still have a valid path through the new DS and new KSK. Give this step the time it deserves as well; DS removals have to clear caches, too. Only after that window closes do you remove the old KSK from your DNSKEY set. Do not rip out the KSK from your zone before the DS changes have safely propagated. That’s a fast track to a validation cliff.

There’s a variant you’ll encounter when migrating DNS providers while staying signed. This is the multi‑signer scenario: both providers serve the same zone content, each with its own ZSK and KSK, and you temporarily publish both sets of DNSKEYs in the zone. At the parent, you publish DS records for both KSKs. Once traffic has shifted and you’re done, you remove the old provider’s DS, then remove their keys from your DNSKEY set. It’s the same rhythm—overlap, test, then prune—just with two signers. This is how we moved a retail brand across platforms on a weekend with zero customer complaints. It felt almost too quiet… exactly the way a migration should feel.

Quick note on algorithms: if you’re changing algorithms for your keys (say from one DNSSEC algorithm to another), the safest route is also “double everything.” Publish both algorithms in DNSKEY and signatures, and carry DS that matches the new KSK. Keep the overlap long enough for caches and old validators to adapt. It’s basically the same game, just with more moving parts.

CDS/CDNSKEY, Registrars, and Doing Less at 2 a.m.

Manual DS updates work, but they’re error‑prone, especially if your registrar’s interface hides digest types or assumes SHA‑1 by default. Whenever possible, I prefer to let the zone speak for itself using CDS and CDNSKEY. This is the “tell the parent what to publish” pattern. Your zone publishes a special record that effectively says, “Here’s the DS you should have for me.” Many TLDs and registrars now honor this, polling your zone and updating DS automatically when they see a valid request that matches a trusted state.

In real life, this means you pre‑publish your new KSK, publish CDS/CDNSKEY that point to it, and wait for the parent to update. You can watch logs or use external checks to see when the DS changes. It’s shockingly calming once you trust it. If your registrar doesn’t support it yet, that’s fine—do the double‑DS by hand and put a reminder in your post‑rollover checklist to turn off any emergency CDS/CDNSKEY you published for the change.

One client of mine moved from a dashboard‑only registrar to one that supports CDS and API updates. The second KSK rotation felt less like surgery and more like a routine chore. If automation is your thing, you might enjoy how we think about automating DNS changes with Terraform and Cloudflare for zero‑downtime deploys. Different layer, same philosophy: set up the guardrails and let the robots be consistent.

Testing Without Lying to Yourself

Here’s my simple rule: don’t test only with your local resolver and declare victory. Caches make optimists out of all of us. When I’m rolling keys, I like to check from multiple angles.

Start by looking at your zone’s DNSKEY set and RRSIGs from authoritative sources. Make sure both keys are really there and both signatures are present when you’re in the overlap phase. Then look at the parent to confirm DS. If you’ve just added a new DS, watch for it to show up across public resolvers. It’s normal for views to drift during the window—that’s the whole reason for the overlap. The end of the test is when no one can build a path through the old key anymore, and everyone can build a path through the new key.

For a visual sanity check, I like using DNSViz. Paste your domain and you’ll see a diagram of the chain of trust, the keys in play, and which path validators will use. It’s so much easier to spot “oh, the parent still points to the old DS” when you can see it. You can also tail your resolver logs if you run one, or query multiple public resolvers during the window. What you’re looking for is consistency after the overlap period ends.

As a final step, I always test real user flows that depend on validation. If you’re using DANE/TLSA for email or any service, send a message or make a TLSA‑validated connection while the rollover is in progress and again after it completes. That way you aren’t discovering a subtle mismatch hours later. If you’re curious about the mail side of DANE and why DNSSEC matters there, I wrote up a friendly walkthrough on SMTP security with MTA‑STS, TLS‑RPT, and DANE/TLSA.

Practical Playbooks: From BIND and Knot to Cloud DNS and Cloudflare

In practice, your exact steps depend on your stack, but the rhythm doesn’t change. If you’re running your own authoritative servers with BIND, inline‑signing and auto‑dnssec can handle the mechanics for you. You generate keys with sane lifetimes, mark them for pre‑publish, set rollover times, and let the signer do the double‑sign and retire dance. I’ve seen people succeed with Knot DNS and PowerDNS too—both have built‑in key management that understands the overlap pattern. The big win is you aren’t manually creating or removing signatures; you’re declaring intent and letting the server maintain validity.

Using a managed DNS provider? Many will handle ZSK rotation for you automatically and guide you through KSK/DS updates. Some even support CDS/CDNSKEY end‑to‑end so DS updates happen without you clicking a thing. If you’re moving between providers, look for “multi‑signer DNSSEC” support. That’s the feature that lets two providers sign the same zone at the same time and makes double‑DS migrations routine. If they don’t have it, you can often still pull it off by temporarily delegating to one as primary with the other as secondary while both have keys published—just make sure your zone content is absolutely identical.

Here’s a small but important side habit: keep your KSK private material safe like you mean it, and back up your signer metadata so a server rebuild doesn’t accidentally rotate keys without telling you. With HSMs this gets easier, but the principle is the same—keys that don’t exist can’t sign, and surprise rollovers are how outages are born.

If this all sounds like the drama of switching production traffic, it is—but calmer. The same zero‑downtime DNA shows up in a lot of places. If you liked this mindset, you’ll probably also like my write‑up on zero‑downtime cPanel‑to‑cPanel migrations. Different tools, same careful overlaps, same feeling of “we never went dark.”

Common Gotchas (and How to Dodge Them Calmly)

Let me share a handful of mistakes I see over and over—usually when someone’s first DNSSEC rollover becomes a firefight.

First, the wrong DS digest. Many registrars let you choose a digest algorithm for the DS. Pick SHA‑256 unless you have a very good reason not to. Publishing a DS that doesn’t match what your KSK can produce is a classic footgun. Validate the DS off your live DNSKEY using a tool you trust before you push it at the parent.

Second, removing old paths too early. Whether that’s a ZSK you pulled from DNSKEY while its signatures are still out there, or a KSK you removed before the old DS aged out at the parent, the result is intermittent SERVFAILs in places you aren’t looking. The antidote is overlap and patience. Do the new thing, wait, then prune.

Third, algorithm mismatch or unexpected changes mid‑rollover. If you change algorithms or key sizes while in the middle of a routine rollover, treat it like a separate project. Double‑sign and double‑DS across the algorithm change, not just across the key ID change. Think in terms of “all validators get a compatible path” and you’ll naturally do the safer thing.

Fourth, tool surprises. I’ve seen signers that quietly decided to resign the whole zone with only the new key ahead of schedule, or dashboards that failed to publish a second DS because someone thought duplicates were an error. Confirm each step in the chain. If you’re using automation, build in a pause where a script checks what’s actually on the wire before moving on.

Fifth, negative caching assumptions. Unrelated on the surface, but if you “test” by querying a name that you recently removed or changed, negative answers can be cached too. That can mislead you into thinking DNSSEC is broken when it’s just your test target. I usually stick to stable names like the zone apex during rollovers to avoid this false alarm.

Emergency Rollover and Going Insecure (When Things Go Really Sideways)

I don’t wish this on anyone, but sometimes you have to assume a key is compromised. The calm path depends on where the compromise happened. If a ZSK is compromised, rotate fast using the same pre‑publish/double‑sign pattern, but with compressed timelines. If a KSK is compromised, your priority is to get the parent DS pointing to a safe KSK as quickly as possible. That usually means pre‑publishing a new KSK and asking the parent to publish a new DS immediately, then removing the old DS. The overlap window shrinks, but you still aim for a moment where both paths work before you cut the old one.

In absolute worst cases, you might need to “go insecure” briefly—removing DS so the chain of trust stops at the parent and your zone answers are treated as unsigned, not bogus. This is tricky and TLD‑dependent. If you ever find yourself here, breathe, document, and favor clarity over speed. The goal is to stop serving a path that can be maliciously validated while you reset. Afterwards, bring DNSSEC back deliberately with the full overlap sequence.

Bringing It Together: A Calm Checklist You’ll Actually Use

Let me wrap all of this into a short narrative I keep in my head. Before any rollover, I check the current TTLs and signature windows, and I make sure I know the parent’s DS TTL. I generate the new key and pre‑publish it in DNSKEY. For ZSK, I double‑sign; for KSK, I add the new DS while keeping the old one. I watch caches with a few simple queries and a visual tool like DNSViz. When I’m confident both paths are visible, I remove the old path—old ZSK signatures first, then the key; old KSK DS first, then the key. I give each removal step enough time to clear caches before touching the next piece.

I also make little bets with myself: “Can I explain this transition to a teammate who doesn’t know DNSSEC?” If I can, it’s probably clear enough to be safe. And I keep notes. The best automation I ever built came from replaying a smooth manual run and baking those assumptions into scripts. If this broader mindset clicks with you, there’s a whole world of zero‑downtime polish to enjoy—from how we keep HAProxy changes live without drama to how we quietly manage certificate strategies.

Wrap‑Up: DNSSEC Rollover Without the Heartburn

If you’ve read this far, you already think the way I like to think: careful overlaps, fewer surprises, and respect for caches you can’t control. That’s the whole game with DNSSEC key rotation. For ZSKs, publish the new key, sign with both, then retire the old key after its signatures are safely out of circulation. For KSKs, publish the new key, add a DS for it at the parent while keeping the old DS, wait for caches, then remove the old DS and finally the old KSK. Slow is smooth, and smooth is fast.

My last bit of advice is to practice when the stakes are low. Try a rollover on a small zone you control. Watch the chain with a visualizer. Build a tiny runbook you trust and turn it into automation. The next time the calendar says “key rollover” or “provider migration,” you’ll pour a coffee, press a few buttons, and wonder why you used to dread this stuff. That’s a good feeling. Hope this was helpful! See you in the next post—and if you want more friendly DNS talk, that piece on apex CNAMEs with ALIAS/ANAME pairs beautifully with this one.