When you setup a new dedicated server, nameservers are some of the most important components. Without nameservers, your server’s websites cannot connect to the outside world. Any type of nameserver errors should be addressed immediately. The following error is a common one:
WARNING: Not all of your nameservers are in different subnets
If you receive this error, it means that both of your nameservers are originating from the same location. In general, this is not necessarily a problem. Your server will probably still work most of the time.
Internet standards, however, dictate that each website have at least two nameservers and that each nameserver originates from a different host. To accomplish this, you can use a DNS host for your nameservers so that they are spread out over diverse locations. Some will even offer this service for free.
The intent of the standard is to keep the Internet running. If one nameserver goes down, people will still be able to access your site because the second, third, or even fourth nameservers are hosted at different locations.
If you absolutely have no way to host your nameservers at different locations, you can configure your own nameservers to use two distinct IP addresses, both originating at your own server, but if your nameservers stop working, no one will see your websites.