DNS Lookup, Reverse DNS Lookup, Domain Configuration Check and IP Address Calculators

Domain Configuration Check

This article relates to the Domain Configuration Check tool. The Domain Configuration Check is a free online tool which performs a comprehensive check of your domain's DNS, email and other configuration.

Simply enter your domain name (eg. example.com) and let the Domain Configuration Check tool start gathering its results. To get started, go to the Domain Configuration Check.

General Name Server Configuration Tests

Name Servers Exist

This check performs a recursive DNS search starting at the root servers of the internet to find the name servers for your domain.

If no name servers are found, it means that this domain is not correctly configured and no further checks can be completed. (Note that just because no name servers are found, this doesn't mean that this domain is not registered).

Name Server Count

This checks that you have at least two name servers configured for your domain.

You should have at least two name servers located in different geographical areas. If one name server was to be unavailable, the other would continue serving requests. If no name servers are responding, visitors will not be able to find your website.

Name Server Glue

Glue records are helper records that need to be provided to help locate your name servers. You will need to provide glue records if your name servers are hosted on your domain name. The glue records are actually additional A records that resolve the name server to an IP address. The parent servers for your domain should return the glue records with your name server records.

There should be a glue record for each name server.

If you are using someone elses name servers, the administrator of the name servers should already have the glue records configured.

Any glue records found are listed in the output, showing the IP address (the country the IP address is assigned to is shown in square brackets). The hostname is shown in round brackets after the IP address.

Name Server Location

Each of your name servers should be located in different geographical locations. This check makes the assumption that if all name servers have an IP address from the same class-C network, then they are located in the same location. This is not necessarily true, so you'll need to decide this for yourself. If you don't know the answer, you'll need to ask your ISP or the people who host your name servers.

Name Server Authority

Each of your name servers should be authoritative for your domain. Any name servers that are not authoritative are called lame name servers. Lame name servers will not provide DNS records (other than cached records) for your domain.

An authoritative name server has an SOA (Start Of Authority) record for each domain it is authoritative for.

SOA Record Consistency

This checks the Start Of Authority (SOA) record for your name servers. Each authoritative name server has an SOA record. This check makes sure that the serial number part of the SOA record is the same for each authoritative name server.

If any name servers have differing serial numbers, it indicates that they don't all have synchronised data. This could be caused by a problem with replication, or replication has not been correctly configured on your name servers.

If this is not corrected, your name servers may return inconsistent data.

Note that if your serial numbers are different, and you have just made changes to your DNS entries, wait a few minutes and try again. Depending on your settings, replication may not have completed yet.

Use Name Server

This shows which name server will be used to run the rest of the tests against. The Domain Configuration Check chooses one name server at random to continue the rest of the tests with. This item shows which name server is being used for the rest of the tests, and lists which other name servers can be used to re-run the tests against.

Only authoritative name servers will be listed here.