Synchronize DNS Records — Simple & Complete Guide

Synchronize DNS Records — Simple & Complete Guide

Synchronize DNS Records — Simple & Complete Guide

Use this tool to fix DNS zones that are out of date across servers in your DNS cluster. The system compares zone files, finds the most current copy, and updates the others so they all match. This is only useful when you have a DNS cluster configured.

Before you start
  • Confirm your DNS cluster is set up and servers can reach each other.
  • Plan a quiet window if you manage many zones (syncs can take time).
  • Have recent backups of critical zones just in case.

Sync Modes (What each option does)

  • Synchronize one zone to all servers — Copy the chosen domain’s latest zone to every server in the cluster. Enter the domain name in the field provided.
  • Synchronize all zones to all servers — Push updated versions of all local zones to every server in the cluster. Best for full re-alignment.
  • Synchronize all zones to this server only — Pull the latest copies from the cluster onto the current server (useful when this server is stale).

Some setups include a checkbox like “Synchronize zones that are not configured on this server.” Enable it to bring over zones that don’t yet exist locally.

Run a Sync (Step-by-step)

  1. Open DNS Functions → Synchronize DNS Records.
  2. Select the mode you need (see above).
  3. If syncing one zone, enter the domain name.
  4. (Optional) Check the box to sync zones not present on this server.
  5. Click Synchronize and wait for completion.

When to use which mode

  • One zone to all servers: One domain is wrong on some servers.
  • All zones to all servers: You want to re-align the whole cluster.
  • All zones to this server: Only this server fell behind and needs to pull updates.

Quick Verification (DNS & HTTP)

Use these checks after syncing:

# Check A/AAAA results from different resolvers
dig +short example.com A
dig +short example.com AAAA

# Ask a specific cluster nameserver directly (replace IP)
dig @198.51.100.10 example.com A

# Confirm the site responds for that Host header
curl -I https://example.com

Troubleshooting

  • Nothing seems to sync: Start a sync from the DNS-only node or target server. Try “all zones to this server only” with the extra checkbox to import missing zones. Verify /var/named/ updates.
  • Only some zones update: Re-run for those domains via one zone to all servers.
  • Cluster roles: Confirm each server’s DNS cluster role and credentials are correct (write/sync).

What this tool actually does

The system compares zone files across the cluster, identifies the most up-to-date copy, and updates the others to match—helping resolve stale DNS answers in a cluster.

Summary

  • Choose the right mode (one zone, all zones, push or pull) based on your issue.
  • Optionally import zones missing on this server during sync.
  • Verify with dig and curl to ensure records match across servers.
  • Check cluster roles/links if syncs don’t run or only partially apply.
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