Tools / Port checker / 53
Is port 53 open?
Port 53 is DNS. Enter your server below to test it from Dallas, Amsterdam and London.
What port 53 is used for
Domain Name System over TCP, used for large answers and zone transfers. Most DNS queries use UDP on the same port.
Should port 53 be open?
Open it only to the addresses that need it. Only authoritative name servers should answer the internet. An open recursive resolver gets abused for DDoS amplification.
How to open port 53
Ubuntu or Debian with ufw, allowing only your own address (replace 203.0.113.10):
sudo ufw allow from 203.0.113.10 to any port 53 proto tcp
Rocky, Alma or CentOS with firewalld:
sudo firewall-cmd --permanent --add-port=53/tcp && sudo firewall-cmd --reload
Windows Server, in PowerShell as administrator:
New-NetFirewallRule -DisplayName "Port 53" -Direction Inbound -Protocol TCP -LocalPort 53 -Action Allow
Then check that the service listens on all addresses, not only 127.0.0.1, and test again above.
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Run your service on a PrivateByte server: a firewall you control and every port yours to open.