ISP only site not accessible if DNS entries missing

I came across an issue with a DNS server which i know the fix, but the symptoms are confusing. I had a DNS Server that was missing the DNS entries in the forwarding lookup. I was able to connect to any website that i entered except for the ISP that provides the primary and secondary DNS addresses. I realize that the server was probably using the public DNS entries by default, 4.2.2.1 and 4.2.2.2, but don't understand why i can access any site except for the ISP.

If anyone can share some light on this, it would be appreciated.

Thanks

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dynamik

The server will just use root hints if forwarders aren't configured. There's no reason why that would prevent you from not resolving the ISPs domain though. Perhaps there are stale or missing records somewhere. You can troubleshoot by using nslookup with the DNS record you're having a problem with and see what IP (if any) is being returned.

JerryL

Thanks for the reply. I think i get what you're saying, but it seems strange that the ISP would be the only site that i can find that would be blocked. Once i entered the DNS settings, i was able to get the ISP immediately (which you would figure anyways).