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Using VPS hosting and dynadot (domain registrar) DNS. Checked domain name with http://www.intodns.com and get some warnings

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

and

Different autonomous systems    WARNING: Single point of failure

As understand to avoid the warning must have second Ip4 address and both the addresses must point to different servers? If both Ip addresses point to the same server, it does not help?

I mean each server has own Ip address. If one server down, then visitors can access website (files) on another server? Is this the reason why need more than one Ip?

Tried to point website to 2 ip addresses and after some time get warning from uptimerobot Connection Timeout

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The warning is about your name servers, not your web servers. –  joeqwerty Nov 9 '13 at 19:37
    
From hosting provider I have only one nameserver. From warning understand that need more than one nameserver. In such case want to understand what will be better if 2 nameservers point to the same server. –  user2118559 Nov 9 '13 at 19:40
    
@user2118559 Using Dynadot, there's only one name server? That should not be the case. Exactly what server do you have configured for your domain? –  Shane Madden Nov 10 '13 at 0:41
    
@ShaneMadden 1) I get warning that only one IP points to my server; 2) I can get second IP from hosting provider; 3) If I point second IP to the same server, what will be better? –  user2118559 Nov 10 '13 at 5:49
    
@user2118559 Which warning are you referring to? Again, the warnings you have put in your question refer to your service provider's DNS servers, not your web server. –  Shane Madden Nov 10 '13 at 7:45

2 Answers 2

up vote 2 down vote accepted

The warning is about the redundancy of your name servers, which are controlled by your provider.

Maybe check with them about their redundancy, but they probably use some kind of anycasting scheme to ensure the availability of the name servers. You can probably just ignore that warning.

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No, just ognoring a warning is always wrong. Anycast is not terribly common, simply assuming that it's used here is wrong. The correct solution is to understand why the warnings are generated and verifying whether they are relevant (if the domain has exactly one server, it may be fine for that one to be the only nameserver - if it's unreachable, everything is anyway, but maybe just the process crashed...). –  Gabe Nov 9 '13 at 22:43
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@Gabe Anycast is extremely common for service providers' DNS servers. But if there's only one server then that's definitely a problem. He's clearly confused between the addresses of his web host and the addresses of his name servers, so it's kinda hard to tell what's actually going on. –  Shane Madden Nov 10 '13 at 0:44
    
@ShaneMadden Hosting provider gives me one Ip address. In dynadot.com the Ip address I wrote as record type A. That is all I did. As result ns1.dynadot.com and ns2.dynadot.com both are related to the same Ip address. As I have seen before ns1 and ns2 usually are related (connected) with different Ip addresses. So want to know if I need to do something (for example place the same files on another server and add another Ip to A record)? –  user2118559 Nov 10 '13 at 6:02
    
@user2118559 ns1.dynadot.com points to 54.214.250.69 and 54.214.250.73, and ns2.dynadot.com points to 54.214.250.74. They only have one entry for your web server, but that's not what the error is talking about. The error is referring to the fact that the dynadot name servers reside in the same network. –  Shane Madden Nov 10 '13 at 7:49
    
Ah, now clear. Then decided to do nothing. Thanks –  user2118559 Nov 10 '13 at 11:15

I suspect this is referring to the fact despite being separate physical or virtual servers they are both on the same subnet/ physical network, if a network specific issue occures then both name servers will be unreachable.

It is good practice to have name servers in physically different networks/locations.

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