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​Recursive DNS server – Everything you need to know

The Recursive DNS server is an important actor within the Domain Name System (DNS). Its work is vital to get answers to the huge number of DNS queries that are sent every minute.

What is a Recursive DNS server?

A Recursive DNS is a seeker of information. It’s the one in charge of seeking the necessary DNS information to respond to the DNS queries sent by users.

What does a Recursive DNS server do?

A Recursive DNS server is constantly busy. Every DNS query becomes a new mission to accomplish for it. There is a user who wants to load a domain, then he or she sends its query through the browser. This is the call for the Recursive to work seeking the associated IP address to that domain. It has a couple of choices to explore for getting that IP address. But the Recursive will keep seeking until it accomplishes its mission. Once it gets the information, it will give it to the user’s browser. Only then will the user be able to load the domain.

The two alternatives a Recursive DNS has to achieve its objective are these:

  1. It will take a look within its cache. Recursive servers can store DNS data but only for a limited time. Domains are different among them, and they have different needs. Based on that, administrators will determine the Time to Live (TTL) for the DNS records. They can set up low or high values that will define the expiration of DNS records.
    To get the answer to a user’s query, a Recursive DNS server will check its cache. If the TTL of the IP address has not expired yet, it will find it and send it to the user’s browser. It will finish its task quickly. But, if the TTL has already expired, the Recursive will have to follow a longer path.
  1. It will search for the authoritative nameserver. A Recursive can communicate with different servers to know which is the authoritative nameserver of the requested domain. Then, it can directly ask the authoritative for the IP address. This alternative takes a bit longer.

Is a Recursive DNS server essential?

Yes, it is! A Recursive DNS is located between authoritative nameservers and the users. Without it, there won’t be a DNS resolution process. Its contribution is essential to find the IP addresses linked to the domains requested by the users. Thanks to their work, millions of DNS queries worldwide get a proper answer.

Does a Recursive DNS server mean any risk?

Yes, unfortunately, cybercriminals know the relevance of its role in DNS resolution and its position between the authoritative and users. This makes it a target to be exploited for launching malicious attacks (DDoS).

Moreover, some Recursive servers are public, meaning their IP address is visible. This makes them attractive and easy victims for criminals.

Conclusion

Now, you know everything about a Recursive DNS server. It works hard for Internet users and your domain.