Network Tools
Work out what an address exposes, who announces it and what its reverse DNS says, then check registration data and IPv6 support. Each tool states what it measured and what it could not.
Network Tools directory
Test a fixed list of 31 common TCP ports on a public host and learn which services are reachable from the internet, with safe guidance for restricting them.
Look up the PTR record for an IP address and confirm that the name resolves back to the same address, the check mail servers commonly apply to senders.
Find the origin autonomous system, announced prefix, registry country and network name for an IP address or host, and learn the limits of that data.
Query RDAP for a domain's registrar, dates, statuses and name servers, or an IP address's network and country, and see what the data does and does not prove.
Check whether a domain's website, mail servers and name servers publish IPv6 addresses, whether IPv6 glue exists, and whether a connection works when possible.
What the network tools answer
These tools start from an address, not from a page. An IP address is a point on the internet with an owner, a routing origin, a reverse name and a set of services listening on it. Looking at it from outside shows what the rest of the world sees, which is often different from what the administrator believes. A firewall rule that was meant to be temporary, a provider-assigned reverse name that does not match a mail server, a CDN edge mistaken for the origin: these are everyday discoveries.
The tools use public, outside-in sources only. They do not log in anywhere, do not test passwords and do not claim to find vulnerabilities.
Choosing the right tool
Pick by the question you are asking.
- What is reachable? The Open Port Checker tests a fixed list of 31 common TCP ports on a public host and explains open, closed, filtered and unknown results.
- What name does this address claim? The Reverse DNS Lookup fetches PTR records and confirms them against forward DNS, which matters for mail servers.
- Who announces this address? The IP ASN Lookup reports the origin AS, prefix and registry data from a third-party source.
- Who registered this domain or network? The RDAP Lookup reads registrar, dates and statuses for domains, and network handles and ranges for IPs.
- Can people reach us over IPv6? The IPv6 Readiness Test checks AAAA records, IPv6 glue and, when the scanner has a route, a real connection.
A typical investigation
Suppose a monitoring alert says a server is exposing a database port. Start with the open port check to confirm which ports respond from outside. If the answer looks like a CDN edge rather than your server, the ASN lookup confirms which network owns the address. If mail from that address is being rejected, look at reverse DNS next. And if a domain looks unfamiliar, the registration lookup tells you the registrar and expiry date. Each step narrows the question without changing anything on the target.
When something needs fixing, the fix usually lives elsewhere: in a firewall, a provider control panel, a registrar account or a DNS zone. Each tool page explains who controls the setting, what could go wrong and how to roll back.
Using these tools responsibly
Test only addresses you own or are authorised to assess. The port check refuses private and non-public addresses and tests a fixed list; it is deliberately not a general scanner. Remember that results are one vantage point at one moment. CDN edges, anycast addresses and load-balanced services can answer differently from other places or at other times. Where data comes from third parties, such as the routing source behind the ASN lookup or the registries behind RDAP, the pages say so, and coverage varies.
Written by DNS Tools editorial · Last updated 2026-10-09