NS servers out of sync, why and how to stop

[mobcdi]

I have 1 server running cPanel which is the authoritive NS for a domain, the secondary ns is outside my control and isn't running cPanel

According to intodns.com my NS's don't agree of the soa serial so my questions are

1. Why, if my autoritive ns has the higher soa serial and is running are some requests not getting correctly responded to?
2. How do I stop my 2 NS's getting out of sync?
3. Can I use the "Synchronizing Dns Zones" option in WHM to push my changes to a NS not running cPanel?

[cPanelDon]

I would consider replacing the secondary NS machine with one that is running either cPanel/WHM or cPanel DNSONLY. cPanel DNSONLY is a free product that allows you to have a fully-functioning DNS server using cPanel DNS Clustering; it is possible to easily configure the two systems in a DNS cluster via WHM, as detailed in the following documentation:
Guide to DNS Cluster Configuration

Here is our product page that describes cPanel DNSONLY in more detail:
Related Server Software - cPanel Inc.

The cPanel DNSONLY installer may be accessed from our downloads page here:
Downloads, Installers - cPanel Inc.

Documentation for setup and our installation guides are located here:
cPanel Installation Guide

[Zaf]

@mobcdi: In case you didn't prefer running cPanel - DNS only, following may help you move at least a step forward to resolve:
0. probably you tried this already, but if you didn't try it.

# rndc reload

1. The sync between NS may have stopped working for one or multiple of several reasons, such as firewall, changed config at either ends etc.
2. If the other server is under your control (completely), then you can ensure either servers aren't firewalling each other whatsoever. Also check your configs to figure if any settings changed recently.
3. I don't think that setting would sync with non-cpanel machine.

Suggest you also check allow-transfer, allow-notify, also-notify settings in named.conf of your cPanel box.

[mobcdi]

Thanks for the reply,

I had a brainwave and remembered that the 2nd NS didn't like comments in the zone file between records and there was 1 there left over from another DNS issue I had so I removed that and now intoDNS: checks DNS and mail servers health has my 2 NS's using listed as using the same SOA record