DNS Lookup

What This Tool Does

This DNS Lookup tool queries DNS records and can compare responses across multiple public DNS resolvers to check propagation consistency, TTL behavior, and resolver-specific differences.

How To Use

1. Enter a Domain or IP:
   • Use a domain for most record types (for example: example.com).
   • Use an IP address only for PTR reverse lookups (for example: 8.8.8.8).
2. Select a Record Type from the dropdown.
3. Choose resolver mode:
   • Propagation ON: compares multiple public resolvers.
   • Propagation OFF: tests one resolver (system default or your custom resolver IP).
4. Optional: enter Custom Resolver IP (like 1.1.1.1) when propagation mode is off.
5. Click Lookup DNS and review the summary, consolidated records, and resolver table.

---

Input Fields Explained

• Domain or IP: target host to query. URLs are normalized to hostnames.
• Record Type: DNS record category to query.
• Custom Resolver (optional): DNS server to use for single-resolver checks.
• Check propagation: compares answers from multiple public resolvers to detect differences.

---

Record Types Explained

• A: IPv4 address record (maps hostname to IPv4).
• AAAA: IPv6 address record (maps hostname to IPv6).
• CNAME: alias record (points one name to another canonical name).
• MX: mail exchanger records for email routing.
• NS: authoritative nameservers for a zone/domain.
• TXT: text records (SPF, domain verification, policy data, etc.).
• SOA: start-of-authority metadata (primary NS, serial, refresh/retry/expire values).
• PTR: reverse DNS mapping from IP address to hostname.
• SRV: service location record (target host/port for services). Example: _sip._tcp.example.com.
• CAA: certificate authority authorization (which CAs may issue certs for the domain).

---

Results Sections Explained

• Successful Resolvers: how many resolvers returned valid answer records.
• Propagation Mismatches: resolvers that differ from majority answer set.
• Unique Records: distinct answers seen after combining all successful resolvers.
• Consolidated Records: merged answer list with TTL and resolver coverage.
• Resolver Responses: per-resolver DNS status and timing details.

---

Table Columns Explained

• Type / Name / Value: the DNS answer contents.
• TTL (sec): cache lifetime in seconds before refresh is needed.
• Coverage: how many resolvers returned that same record.
• Status: whether resolver returned usable answer data.
• Response Code: DNS response from resolver (for example NoError, NotExistentDomain, Refused, ServerFailure).
• Authoritative: indicates authoritative answer flag from response header.
• Recursive: indicates recursion availability flag from resolver.
• Latency: query round-trip time to that resolver.
• Propagation: whether resolver matches consensus answer set.

---

How To Interpret Propagation

• All “Matches”: propagation is consistent across tested resolvers.
• Some “Different”: propagation is still in progress or cached records differ.
• No Data on some resolvers: resolver may not have updated cache, record may not exist there yet, or query policy may differ.
• Lower TTL generally means caches should refresh sooner after DNS changes.

---

Common Response Codes

• NoError: query completed without protocol error (answers may still be empty).
• NotExistentDomain (NXDOMAIN): domain does not exist.
• Refused: resolver refused the query.
• ServerFailure: temporary resolver or upstream failure.
• NotImplemented: operation/type not supported by resolver.

---

Troubleshooting Tips

• If non-PTR query fails, ensure you entered a domain and not an IP.
• If PTR query fails, ensure input is a valid IPv4/IPv6 address.
• For SRV, include full service label (for example _service._proto.domain.com).
• After DNS updates, re-check over time until mismatches disappear.
• If using a custom resolver, verify the resolver IP is reachable and valid.