There have been situations where a particular website shows one version in Verizon ISP in the USA and a different version in Airtel ISP in India. Basically, a single website resolves to multiple servers because of faulty nameserver configurations.
Especially, if you are using custom nameservers via a Virtual Private Server and have created nameservers like ns1.yourdomain.com and ns2.yourdomain.com this problem arises many times. I am providing the exact solution to fix this issue. In my case, the hosting company (Supreme Server), Domain registrar (GoDaddy) and ISP (Verizon) kept blaming each other and no one even tried to find a solution to this problem.
Redundant nameservers issues when migrating servers
This happened when we migrated the server from old host HostGator to new host Supreme Servers. We were moving from a shared hosting environment to a VPS environment when this problem occurred. While some internet service providers showed fetched our website from the new servers other ISPs still continued to pull content from the old server. As a result the client was in a fix and sales were down. SSL errors started coming in too and idiots at GoDaddy customer care promptly blamed it on the SSL.
But, I knew it well, it was not an SSL issue. I looked at the nameserver records first.
Error : Your local nameservers contain NS records with IP’s not listed by the parent nameservers. The results of this are undefined in the DNS specifications, and it indicates configuration problems. The following nameservers are stealth nameservers:
Note the highlighted areas, the child name servers or local name servers are still fetching old values somehow.
So I knew I had to find it somewhere. The hosting folks told me to set the IP correctly on your registrar. But it was perfectly fine on GoDaddy and that is fact is the parent nameserver. So I crossed out that option.
I logged in to WHM of the virtual private server and looked for all DNS options. After a while, I found this on Nameserver Record Report feature of WHM.
What I can guess right now is that, when we set up a new host on WHM and create these nameservers through hostnames on the domain registrar there is a time lag till all servers are updated with the new time servers. During that period the nameserver probably pull up old nameserver values from the old host stored at the domain registrar or other name servers.
So, these need to be edited. So I looked up Edit DNS functionality on WHM.
I have updated the old fields with correct nameservers now. But after doing it, I started getting a different error on nameserver / dns audit sites.
So now the old nameserver details are gone but its not fetching the right IP details yet. So next step is to add new DNS records as local nameservers. So search for DNS Functions then open Add a DNS Zone. It would look something like this.
Provide the IP address of your hosting, put the full host name (nameservers that you have created already) and select which domain or account do you want to associate this hostname with. Create both ns1.yourdomain.com and ns2.yourdomain.com and that should fix all your troubles.
If we are on Amazon Hosting (AWS), we notice this issues less frequently than on shared hosting Cpanel/WHM. I have often discussed this problem with students at our AWS Developer Certification Course in Delhi