Description
The domain name system (DNS) stores and associates many types of information with registered domain names (like declude.com). It also translates domain names to IP addresses and records the mail servers that accept mail for each domain.
The DNS Lookup test performs a standard DNS lookup, and returns details about the specified record type(s) as well as additional useful information about the domain's DNS entries.
Example: For the A record type, a DNS lookup provides information about how the domain or host name (example, bosons) is resolved to an IP address (example, 66.151.183.21).
How it works
A domain name query packet is sent to a designated (or defaulted) DNS server, and may be referred to multiple DNS servers along the way to get to the server holding the information about the domain (i.e., the local DNS name server at your service provider, an intermediate name server, or one of the root servers for the entire domain name system hierarchy). We provide a list of the servers involved in the search and a link to the complete DNS traversal if you'd like to verify that all DNS servers are reporting the same results.
Note: The DNS Lookup test is done in real time and does not rely on cached information.
Caution: Some DNS servers are unfortunately set up to 'lie' and will not return all the DNS records for a specified host name.
Common Uses
- To Verify Your DNS Entries
Typically, you'll use this tool to make sure that your DNS entries are correct (for example, making sure that the A record for your domain points to the IP address of your website). - To Determine the Mail Servers for Particular Domain
You might use this tool to find out what server(s) accept E-mail for a specific domain (by doing an MX record lookup). - To Determine Whether the Domain Restricts Who Can Send E-mail
You might use this tool to determine the SPF record for a domain (by looking up the TXT record for the domain), to see if the domain tries to restrict who can send E-mail using the domain.
Advanced Features
The advanced version of the DNS Lookup tool includes Server lookup and customized view options.
The Server field lets you pick a specific DNS server to use (for example, if you are setting up a new DNS server that nobody yet uses, you can check to see how it would respond to DNS queries).
The View dropdown allows selection of different output formats. For example, if you are used to using the 'dig' DNS program, the dig output may be easier for you to understand.
How to Use
- Enter a domain or host name (example: boston.com or www.boston.com).
- Select a DNS Record Type from the dropdown list.
- Click Lookup.
Results
The results displayed for the DNS Lookup test include the following (broken down by sections):
How I am searching...
Resolving the DNS Lookup request usually requires recursing through several DNS name servers to find the needed information. Each name server points to the next server to query. This information is displayed, showing how the search was performed and how long each request took to complete.
Response
The information returned by the final name server is listed in a table.
| Domain | Type | Class | TTL | Answer |
|---|---|---|---|---|
| boston.com | A | IN | 3600 | 66.151.183.21 |
| boston.com | NS | IN | 3600 | ns-a.pnap.net |
| boston.com | NS | IN | 3600 | ns-b.pnap.net |
| boston.com | NS | IN | 3600 | ns-c.pnap.net |
| boston.com | NS | IN | 3600 | ns-d.pnap.net |
| ns-d.pnap.net | A | IN | 43200 | 64.94.123.4 |
| ns-d.pnap.net | A | IN | 43200 | 64.94.123.36 |
| ns-d.pnap.net | A | IN | 43200 | 64.95.61.4 |
| ns-d.pnap.net | A | IN | 43200 | 64.95.61.36 |
Domain
The domain or host name specified for the test (at the top of the list) and the domain or host names of other records provided by the answering nameserver.
DNS Record Type
The DNS Record Type specified (at the top), and the record types for other records displayed. Possible record types: A, AAAA/IPv6, CNAME, MX, NS, PTR, SOA, SRV, TXT.
Class
In most cases, IN - which stands for the Internet. Possible classes: IN, CH, HS.
TTL
Time to Live - the amount of time other DNS servers and applications are allowed to cache this record.
Answer
The mapping information associated with the specified domain or host name. Example, if A record was selected, this would be the IP address of the host associated with the specified domain or host name in that record.
DNS Traversal (via link)
If you'd like to make sure that all DNS servers are reporting the same results, a link is provided to the DNS traversal. The traversal shows the responses and response times for the same requests to all the parent servers for the TLD (example, .com if boston.com) provided by the root server (requesting name server info for boston.com). Next, the responses and response times are displayed for requests made to all the parent servers resulting above (the parent servers for boston.com) for the requested record information. To summarize, the DNS resolver:
- queries the root servers for the NS record list (parent servers) for the TLD (.com)
- queries each of those servers for the parent servers for boston.com
- queries the next set of servers for the specified record type info for boston.com