DNS · IPv4 · IPv6

The Internet can be reachable while the service still isn't.

Validate DNS, IPv4 and IPv6 behaviour separately so name resolution and network reachability do not hide each other’s failures.

A DNS problem should not make your monitoring blind.

See DNS validation in action Explore Broadband

REAL-WORLD EXAMPLE

When “half the Internet” seems unavailable, separate DNS from connectivity.

Customers reported that many Internet services were unreachable.

Expected path

Observed path

Finding: DNS result and actually available connectivity did not match.

Degust validates DNS and direct network reachability separately, so investigation can continue even when DNS itself is part of the problem.

SEPARATE THE SIGNALS

Name resolution and network reachability are different questions.

DNS

Name resolutionValidate

Returned addressesInspect

Response behaviourCompare

AvailabilityObserve

NETWORK REACHABILITY

IPv4Validate directly

IPv6Validate directly

Direct target reachabilityCheck independently

Path evidenceCollect where configured

A successful DNS response does not prove that the returned path is usable.

DUAL-STACK VALIDATION

Validate IPv4 and IPv6 independently.

IPv4Check whether services remain directly reachable over IPv4.

IPv6Check whether IPv6 connectivity supports the addresses and services being returned.

DNSValidate name resolution without depending on it for all other network checks.

ComparisonCompare affected locations with similar locations using different DNS or connectivity conditions.

Related insights

FROM DNS RESPONSE TO EVIDENCE

Separate resolution, reachability and service outcome.

RESOLVE

Validate the DNS response.

REACH

Check IPv4 and IPv6 connectivity independently.

VALIDATE

Check the actual service outcome.

COMPARE

Identify which locations or conditions share the failure.

DNS AND DUAL-STACK QUESTIONS

Questions operators ask about DNS, IPv4 and IPv6.

Separate signals make partial and dual-stack failures easier to investigate.

How can an ISP tell whether an Internet problem is caused by DNS or by connectivity?

Validate name resolution and direct network reachability separately. Comparing DNS results with IPv4, IPv6 and service checks shows whether the failure begins with resolution, connectivity or the service path.

Can DNS work while the returned IPv6 service path is unusable?

Yes. A DNS response can return an IPv6 address even when the corresponding path is impaired. A successful response therefore does not prove that the returned service path is usable.

How can DNS be monitored without making all network monitoring depend on DNS?

Combine DNS validation with direct checks to configured IP targets. This preserves independent reachability evidence when name resolution itself is unavailable or inconsistent.

Why should IPv4 and IPv6 connectivity be validated separately?

Dual-stack services can behave differently over each address family. Separate validation reveals failures that a combined or fallback result could otherwise hide.

How can DNS problems make only some websites or services appear unavailable?

Different domains, returned addresses, caches and service paths can produce different outcomes. Comparing affected targets and locations helps identify the shared DNS or connectivity conditions.

How can an ISP detect DNS problems affecting only part of its customer base?

Group distributed results by region, resolver, access technology or other available context and compare affected locations with similar locations that remain normal.

How can customer-side validation help identify DNS or dual-stack problems?

Validation from customer-side locations captures the resolver and connectivity conditions that subscribers actually use, making regional or access-specific patterns visible.

How can an ISP compare provider DNS with external reference DNS?

Run the same defined resolution checks against the provider resolver and an approved external reference, then compare response behaviour and returned data. The comparison is evidence, not a universal resolver policy.

Can Degust continue analysing network reachability when DNS itself is impaired?

Yes, where direct non-DNS-dependent targets are configured. DNS and direct reachability can be validated separately so one failure does not remove all network evidence.

Know whether DNS, IPv4 or IPv6 is actually failing.

Separate name resolution from network reachability and service validation before the next customer complaint becomes a guessing game.

See DNS validation in Degust Explore Broadband