Symptoms
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Plesk website opens with one of the following errors in a browser:
This site can’t be reached
ERR_NAME_NOT_RESOLVED
DNS_PROBE_FINISHED_NXDOMAIN
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DNS Server is enabled in Tools & Settings > Services Management and no errors are provided on its restart.
Cause
The port 53 (TCP or UDP) is filtered by a firewall for incoming or/and outgoing connections for the Plesk server's IP address:
# nmap -p53 203.0.113.2
PORT STATE SERVICE
53/tcp filtered domain
# nmap -sU -p53 203.0.113.2
PORT STATE SERVICE
53/udp open|filtered domain
Resolution
Allow inbound and outbound connections on port 53 (TCP and UDP) in a firewall.
Configuring firewall rules in case Plesk Firewall is used
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Make sure that Plesk Firewall is installed. If required, enable it to open all ports needed by Plesk automatically.
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If Plesk Firewall is installed and enabled, however, the rule Domain name server is missing, add a custom rule for opening port 53 as per the article.
Configuring firewall rules via SSH (for Plesk for Linux)
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Connect to the server via SSH.
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Open port 53 (UDP and TCP) for incoming and outgoing connections in the local firewall:
- For
iptables:
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Open port 53 in
iptables:# iptables -I INPUT -m tcp -p tcp --sport 53 -j ACCEPT
# iptables -I INPUT -m udp -p udp --sport 53 -j ACCEPT
# iptables -I INPUT -m udp -p udp --dport 53 -j ACCEPT
# iptables -I INPUT -m tcp -p tcp --dport 53 -j ACCEPT -
To apply changes execute the command below:
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for RHEL-based OSes:
# service iptables save
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for Debian-like OSes:
# iptables-save > /etc/iptables/rules.v4
-
-
For
firewalld:# firewall-cmd --permanent --add-port=53/tcp
# firewall-cmd --permanent --add-port=53/udp
# firewall-cmd --reload
- For
Configuring firewall rules in Windows Firewall (for Plesk for Windows)
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Connect to the server via RDP.
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Go to Start > Control Panel > Windows Defender Firewall > Advanced Settings.
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Open the Inbound Rules and make sure that the following rules are enabled:
Add them manually if required.
Note: If after applying the above steps port 53 is still shown as filtered (closed) in an online port checker (for example, ping.eu), that means that port is being filtered on a hosting/Internet service provider side. Please, contact your hosting/Internet service provider and ask them to open these ports for you.