DNS records are not synced to slave servers using Slave DNS Manager extension in Plesk: Invalid IP address: zone may fail to transfer to slaves

Symptoms

• DNS records are not synced to Slave servers in Plesk
• Slave DNS manager extension is used.
• Plesk UI shows that data synced successfully
• Messages like below appear in the system log when resyncing records through the Slave DNS manager extension:

CONFIG_TEXT: zone example.com/IN: zone serial (2022091608) unchanged. zone may fail to transfer to slaves.
plesk named[1181]: zone example.com/IN: loaded serial 2022091608
plesk named[1181]: zone 203.0.113.in-addr.arpa/IN: zone serial (1663336305) unchanged. zone may fail to transfer to slaves.
plesk named[1181]: zone 203.0.113.in-addr.arpa/IN: loaded serial 1663336305
plesk named[1181]: zone example.com/IN: sending notifies (serial 2022091608)
plesk named[1181]: all zones loaded
plesk named[1181]: running
plesk dnsmng[69408]: : invalid IP address

Cause

Bind9 cache contains outdated/incorrect data.

Resolution

Flush Bind9 cache and reload services:

1. Connect to the server via SSH

2. Flush cache and reload configuration files/zones:

# rndc flush && rndc reload

3. Restart named/bind service

• On RPM-based OS (CentOS/CloudLinux/RHEL/AlmaLinux/Rocky Linux):

# systemctl restart named-chroot.service

• On Debian/Ubuntu:

# service bind restart