In DNS check tools like intodns and dnsstuff, what are the following warnings means and how to avoid:

Different subnets : WARNING: Not all of your nameservers are in different subnets.

Number of MX records OK. Looks like you only have one MX record at your nameservers. You should be careful about what you are doing since you have a single point of failure that can lead to mail being lost if the server is down for a long time.

What is required in hosting environment/server to help have name servers and MX in different SubNets?


Different subnets: it's best to spread your nameservers around on the internet, so that if one of your networks goes down, at least clients can still resolve your names. The same goes for having a fallback for your actual services of course, or the point is moot.

MX records: Same story really. Have more than one mailserver, so you can take one down for maintenance.

  • thank you ... is it possible when you have both NS on IPs point to the same dedicated server .. what should I ask for when contact hosting support? and where exactly can I read a simple tutorial about this? .. thanks – hsobhy Mar 29 '13 at 22:07
  • Well, you can do that, but then that one server becomes a single point of failure. The very simple tutorial would be "Don't have single points of failure anywhere you can avoid them" :) – Dennis Kaarsemaker Mar 29 '13 at 22:11
  • okey, since i'm not IT person .. I think what I understand is to have 2 physical machines working as hosting servers each have the DNS & Mail/MX and host my domains on both of them using different records/SubNets .. is it close to the right? – hsobhy Mar 29 '13 at 22:15
  • just wished to know what is required in hosting environment/server to help have name servers and MX in different SubNets? – hsobhy Mar 29 '13 at 22:18
  • More servers, more connections to the internet. But you have to ask yourself whether that is worth it. What you're doing seems to be more a hobby project (and thus technically offtopci here) instead of trying to engineer a highly available system. – Dennis Kaarsemaker Mar 29 '13 at 22:35

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