How to Fix Plesk DNS Record Timeout and "rndc: connect failed" Error Make it Rain Paper

Pre-requirements

• Access to the Plesk control panel as an administrator.
• Ability to enable debug mode in Plesk.
• Basic knowledge of DNS and server network configurations.
• Root or sudo access to the server (for running network troubleshooting commands).

Issue

When attempting to change or add DNS records in Plesk, the page times out, but the changes are still applied. The following error message appears in /var/log/plesk/panel.log when debug mode is enabled:

Error code 1: rndc: connect failed: 203.0.113.2#953: timed out

Cause

This issue typically occurs when Plesk cannot connect to one of the slave DNS servers due to a network issue or a closed port (TCP port 953 in this case).

Resolution

To resolve the issue, verify the network connection between the Plesk server and the slave DNS server and ensure that TCP port 953 is open on the slave server.

Steps to Troubleshoot Network Issues

1. Enable debug mode in Plesk:

plesk bin server_pref --update -debug true

1. Check the connection between the Plesk server and the slave DNS server by running nmap:

nmap 203.0.113.2 -p 953

• If port 953 is shown as "open," the connection is working.
• If port 953 is "filtered" or "closed," proceed with the steps below.
1. On the slave DNS server, verify that TCP port 953 is open and accessible. You can use firewalld or iptables to check and modify the firewall settings.

# For firewalld:
firewall-cmd --zone=public --add-port=953/tcp --permanent
firewall-cmd --reload

# For iptables:
iptables -A INPUT -p tcp --dport 953 -j ACCEPT
service iptables save

1. Ensure the DNS server (BIND) is running on the slave server:

systemctl status named

1. Test the connection again using nmap or telnet:

telnet 203.0.113.2 953

1. Disable debug mode in Plesk once the issue is resolved:

plesk bin server_pref --update -debug false

Gotchas to Avoid

• Ensure the correct IP address is being used when troubleshooting connection issues.
• Confirm that port 953 is not blocked by any intermediate firewalls or routers.
• Verify that the DNS server is properly configured and running on the slave server.

Linux Commands to Verify DNS and Network Status

• Check DNS Status:

systemctl status named

• Check Network Ports:

nmap 203.0.113.2 -p 953

Pre-requirements

• Root or sudo access to the Plesk server and any associated DNS servers.
• nmap installed on your Linux server.

What is nmap?

nmap (Network Mapper) is a network scanning tool used to discover hosts and services on a computer network. It helps in identifying open ports, available services, and any potential security vulnerabilities.

Steps to Use nmap for DNS Troubleshooting

1. Install nmap if it’s not already installed:

# For Ubuntu/Debian:
sudo apt-get install nmap

# For CentOS/RHEL:
sudo yum install nmap

1. Run nmap to check if TCP port 953 is open on the DNS server:

nmap 203.0.113.2 -p 953

1. Analyze the results:
• If the port is "open," the DNS server is reachable.
• If the port is "closed" or "filtered," check