Could we configure DNS to use TCP ?

Posted on 2009-05-06
Last Modified: 2012-06-27
I feel by default DNS uses UDP protocol on port 53. Could we configure it to let it use the TCP as well ? /etc/services shows it support both TCP and UDP.
bash-3.00# grep 53 /etc/services 
domain          53/udp
domain          53/tcp

Open in new window

Question by:beer9
LVL 48

Expert Comment

ID: 24312665
Depends what DNS server you are running.

Author Comment

ID: 24314160
What if I am using BIND, does is support both TCP and UDP by default? Thanks!
LVL 62

Expert Comment

ID: 24314213
DNS over TCP is almost never used.
Any server out there supports DNS over TCP but no clients use that by default.
Since it is that rarely used I suspect more problems in there.
Does Powershell have you tied up in knots?

Managing Active Directory does not always have to be complicated.  If you are spending more time trying instead of doing, then it's time to look at something else. For nearly 20 years, AD admins around the world have used one tool for day-to-day AD management: Hyena. Discover why


Accepted Solution

jarrell earned 250 total points
ID: 24315868
Generally TCP uses UDP for speed, but if the answer doesn't fit into a single udp packet, it'll switch to using TCP.  Which I've seen cause problems with some clients; we broke some software when our SPF record (which is in a TXT on the domain names RR) got too big, and we were doing TCP all of a sudden.
LVL 62

Expert Comment

ID: 24318808
It depends on client. Some servers do send chain of UDP packets with huge record...

Author Closing Comment

ID: 31578360
Thank you :-)

Featured Post

Ransomware: The New Cyber Threat & How to Stop It

This infographic explains ransomware, type of malware that blocks access to your files or your systems and holds them hostage until a ransom is paid. It also examines the different types of ransomware and explains what you can do to thwart this sinister online threat.  

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Let's say you need to move the data of a file system from one partition to another. This generally involves dismounting the file system, backing it up to tapes, and restoring it to a new partition. You may also copy the file system from one place to…
My previous tech tip, Installing the Solaris OS From the Flash Archive On a Tape (, discussed installing the Solaris Operating S…
Learn how to get help with Linux/Unix bash shell commands. Use help to read help documents for built in bash shell commands.: Use man to interface with the online reference manuals for shell commands.: Use man to search man pages for unknown command…
Learn how to navigate the file tree with the shell. Use pwd to print the current working directory: Use ls to list a directory's contents: Use cd to change to a new directory: Use wildcards instead of typing out long directory names: Use ../ to move…

810 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question