What is DNS Port?

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You might have heard about DNS servers, but what is a DNS port? This guide will explain it in detail and share some other associated aspects. So, continue reading till the end and find everything you need to know about a DNS port and how to use it. 

What is this DNS Port? 

A DNS port is the port assigned by the DNS server you are using. The most commonly used DNS port there is UDP 53. This port is the default for all queries associated with the domain name system. 

UDP is much lighter and faster than TCP and can significantly limit the performance overhead on all DNS servers. The zone servers in the domain name system rely heavily on TCP port 53 due to the fact that TCP is more reliable. But TCP is slower, and it uses far more bandwidth. 

This DNS zone transfer usually occurs on the side of the DNS server. And the DNS port is critical because it enables systems to communicate with one another with the help of domain names rather than IP addresses. 

Using the Dig Command to Query DNS Record

The Dig command is powerful in Linux OS for all query DNS information. You can use this particular command to query A record for any domain name. This command will query the DNS server using the UDP protocol by default.

How Does This DNS Query Work?

Domain name system communications take place using two different types of messages. These include queries and their replies. Both query format and replay format in DNS contain various sections, 

Header section

This section has a flag, identification, numbers of questions and answers, authority resource records, and various other records. 

Flag section

This section has different subsections of 1 or 4 bits. It indicates the type of message and authority name, server, and status. It indicates whether the query is recursive or the request was truncated or not.

Question section

This section contains the DNS record type and domain name to be resolved. Each label within the domain name is prefixed based on its length. 

Answer section

This section has the record of the query name. 

Capturing DNS Query on UDP 53 with the Tcpdump command

The “Tcpdump” command is powerful in Linux for capturing packets. You can use this command to capture these DNS packets. 

Private DNS Servers

Using the above example, you can see that you can conveniently capture all domain name system data using the Dig command. Your internet service provider records all DNS queries you make on the internet because they are legally required to do so for a long time. 

Private DNS servers can safely handle all these domain name server requests and keep every other party out of the loop. Your internet service provider will only know that you have logged into these servers. 

These private DNS servers for various DNS server providers can encrypt all your online traffic and protect all your DNS requests from any third parties. 

No third party can spy on you secretly and redirect your information to any malicious sites. Moreover, you can also benefit from the lightning-fast resolution times of your domain name system. 

DNS Zone Transfer Utilities TCP Port 53

Many firms have different DNS servers. And these servers will exchange info with one another within zone transfer. While the main DNS server, referred to as the master DNS server here, will replicate all this domain name system information. 

It is eminent as the primary zone and replicates the secondary zones. This main server is classified as an authoritative server for this domain. The transfers connect to Port 53 and utilize TCP with a transport layer to guarantee transfer delivery. 

It usually happens on the domain name system server side. But you can use it to get all the records for a single domain. 

dig axfr zonetransfer.me @nsztm1.digi.ninja

;; XFR size: 50 records (messages 1, bytes 1994)

From this result, you can see that the DNS zone file has 50 records.

DNS Query with Encryption Using HTTPS Port & TLS Port

Conventional DNS queries and answers are sent using TCP and UDP without encryption. This is prone to spoofing and includes internet filtering using DNS services. 

DNS with SSL and HTTPS are the standards developed to encrypt plain text domain name system traffic to prevent malicious attacks, advertisers, internet service providers, or other entities from interpreting the info. DNS with TLS uses port 853, and DNS with HTTPS uses port 443. 

FAQs

Is there a way to capture a DNS query with all records? 

You can use the “Tcpdump” command for capturing a DNS query on UDP 53. It is a powerful command, and it can capture DNS packets. You can also use the “dig” command with this one. 

Why are private DNS servers useful?

Your internet service provider maintains a record of all your DNS requests. And if you want to keep them away from the access of your ISP, you will need private DNS servers because they encrypt these requests. 

What can we use the “Dig” command for?

The “dig” command is a powerful command that you can use in Linux OS to query domain name system information. For example, you can use it on a record for a specific domain name. 

Conclusion

A DNS port is the port that DNS servers assign, and the most frequently used port for this purpose is UDP 53. This is a default port for all queries and zone transfers with better speed and performance, and it will help establish communication between computers without using IP addresses.