LEARN. PRACTICE. GROW.1. Define what each control proves
DNSSEC validates the origin and integrity of signed DNS data. It does not encrypt the queried name or classify the destination as appropriate for the organization. A malicious domain can have a valid DNSSEC chain. DNS Firewall makes filtering decisions for queries passing through VPC Resolver; that decision serves a different purpose. Draw the clients' actual resolution path and identify where recursion happens. An application using another resolver is not automatically covered by the same rule-group association. Nor should AWS Network Firewall be assumed to inspect queries to VPC Resolver. Define separate criteria for data authenticity, name-policy results, application transport and operation authorization. This separation prevents attributing every SERVFAIL to one component or accepting a filtering policy merely because name resolution succeeds.
2. Establish trust with explicit dependencies and timing
Activation requires coordination between the zone operator and whoever publishes the DS in the parent zone. Before the change, record TTLs, baseline queries, owners and observation methods. The KMS key backing the KSK has specific requirements: us-east-1, asymmetric ECC_NIST_P256 and SIGN_VERIFY usage, plus the necessary permissions. After enabling signing, confirm authoritative propagation and allow previously cached data to expire before establishing the chain through the DS. INSYNC does not clear external resolver caches. Lowering a TTL now does not retroactively shorten the lifetime of an earlier cached answer either. In the change meeting, distinguish configuration time from observation time and the parent-zone owner's availability. A technically short operation can therefore require a longer coordinated rollout with explicit evidence at each stage.
3. Recover without breaking the published chain
If the DS remains published or cached, disabling signing can make answers invalid for DNSSEC-validating resolvers. For planned withdrawal, remove the DS from the parent, confirm propagation and wait its TTL before disabling signing. The local model calculates only this timing condition from supplied evidence; it does not query DNS or guarantee convergence across the Internet. A KSK ACTION_NEEDED alarm can indicate lost access to the KMS key. Some queries may still work while valid signatures remain, so waiting for a complete outage is an unsuitable response criterion. Investigate key state and permissions, apply the documented recovery procedure and observe resolution. AWS-managed ZSK rotation does not remove responsibility for the key backing the KSK. Assign the alarm to an owner who can actually restore the required access.
4. Interpret validation on the hybrid path
When VPC Resolver performs recursion for public names, its validation configuration can check DNSSEC. If a query is forwarded to another resolver, that recursive upstream must perform validation. Enabling the VPC option alone does not establish validation on the forwarded path. DNS-bit behavior is also specific: VPC Resolver ignores DO and CD and does not return the AD bit or DNSSEC records to the client, even while validating. Therefore, missing AD in a capture is insufficient to declare validation disabled, and CD does not provide a per-query bypass here. For acceptance, use controlled test names and expected results, distinguish valid from invalid answers and confirm the configuration of the component actually doing recursion. Document the boundary so that an on-call engineer does not diagnose a forwarding issue from the VPC checkbox alone.
5. Apply filtering with coverage and precedence
Creating rules is insufficient: the rule group needs a VPC association and exists within the appropriate Region. Lower numeric priority is evaluated first. Allow and Alert terminate inspection of the query; Alert permits it and records the outcome, so a later blocking rule does not automatically turn that result into denial. A list containing example.com does not necessarily cover the intended subdomains; specify the pattern and test the exact application name. For CNAME chains, the redirection inspection setting requires attention to subsequent names. Trust within one transaction does not grant trust to an independent client query for the target. Include the initial name, directly queried target, relevant A and AAAA types and resolution in each production Region in the acceptance plan.
6. Choose failure behavior and observe its effect
Fail closed is the default when Resolver receives no response from DNS Firewall: it returns SERVFAIL. Fail open permits queries under that condition and requires an explicit continuity-versus-control decision. This setting does not turn invalid DNSSEC data into trusted data. In a Block rule, NXDOMAIN, NODATA and an override response produce different client outcomes; do not treat them as equivalent diagnostic evidence. During a pilot, Alert helps observe impact, but promotion to Block should include reviewed exceptions, an owner and rollback. EventBridge events are not an exact query counter because repeated events for the same domain are limited within a six-hour window. Hand RUN test queries, expected results, logging configuration and contacts. Correlate DNS evidence with the effect on the batch without inferring business success from an isolated answer.
def signing_removal_gate(parent_ds_present, propagation_confirmed_at, ds_ttl, now):
if parent_ds_present or propagation_confirmed_at is None:
return "hold: parent removal not confirmed"
if ds_ttl < 0 or now < propagation_confirmed_at:
raise ValueError("invalid supplied timing")
if now - propagation_confirmed_at < ds_ttl:
return "hold: DS cache interval remains"
return "timing gate met: validate remaining runbook checks"
assert signing_removal_gate(True, None, 600, 1000).startswith("hold: parent")
assert signing_removal_gate(False, None, 600, 1000).startswith("hold: parent")
assert signing_removal_gate(False, 1000, 600, 1599).startswith("hold: DS")
assert signing_removal_gate(False, 1000, 600, 1600).startswith("timing gate met")
try:
signing_removal_gate(False, 1000, -1, 1600)
except ValueError:
pass
else:
raise AssertionError("negative TTL accepted")
print("five timing checks passed; no DNS query or signing change performed")
Fictional case: a portal zone is signed, but a key-policy change puts the KSK in ACTION_NEEDED. The portal still resolves. The team handles the alarm before signatures expire, restores documented access and validates external queries. It does not immediately remove signing while the parent still contains the DS.
Common pitfalls
Confusing signing with encryption or reputation; disabling signing before removing DS; treating missing AD as proof of failure; treating Alert as blocking or events as every query.
Related topics: DNS delegation and TTL · Key management and alarms · Acceptance and rollback
DNS trust and filtering have distinct conditions and evidence. Recovery must respect the trust chain and caches.
Reference: Configuring DNSSEC signing · ANS-C01