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  1. #1
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    How resolves child name servers, the registrar or host?

    My boss asked me this question and I don't have a straight answer. It basically was regarding some dns setup. I was always confused but now I think he is going to fire me because i lied him that the setup was correct i made.


    Basically every domain registrar allows to setup a child name like ns1.example.com and n2.example.com, where you registered the domain.

    So you would put the IP of DNS server 1 in ns1.example.com and the IP of ns2.example.com

    .com is resolved by a root dns, but my question is why do you set up the child name in the registrars in the first place?

    You still need to setup the same name server on your dns server, and even an A record that points to it. So my question is now:

    How is actually resolving the dns name ns1.example.com? Is it the registrar or the dns server? If its the registrar i dont see a problem but if its the dns server im in big trouble and im going to be fired if i dont change this.

    Now lets assume DNS 1 crashed, that would not be a problem for exampleB.com using those names, since it would have DNS 2 or ns2.example.com to resolve.

    But if example.com was actually hosted on that server how will this work? I mean if the domain itself example.com is not working I suppose ns1 and ns2 will not work as well unless its the registrar resolving it. So that is my question. Its like a cicle around. If server that has DNS server 1 hosts that domain crashes, DNS 2 will still be up but the domain itself will not be resolving. PLease guys. I need to set up this straight and I have a deadline.

    Even if example.com is on a third server, that would still make a single point of failure.
    Last edited by nibb; 10-13-2009 at 09:18 AM.

  2. #2
    Let me first explain you the dns resolving so that the confusion is cleared. Suppose you register example.com with name servers ns1.example.com you make this entry at the registrar level. You will be giving the ip of ns1.example.com too. The registrar makes this entry to the root name servers. So now when you browse example.com it will first check with the root nameservers the nameservers registered. In this case it is ns1.example.com which will be pointed to the ip given. Hence now the request will be sent to the nameserver and then the resolving happens.

    Now coming to your next question regarding point of failures. It is not necessary that you should have ns1.example.com to be of the same server as example.com. This could be anything else. I think you have got this query resolved too by now. It is the registrar that resolves the nameservers.

  3. #3
    Quote Originally Posted by nibb View Post
    So my question is now:

    How is actually resolving the dns name ns1.example.com? Is it the registrar or the dns server? If its the registrar i dont see a problem but if its the dns server im in big trouble and im going to be fired if i dont change this.

    Now lets assume DNS 1 crashed, that would not be a problem for exampleB.com using those names, since it would have DNS 2 or ns2.example.com to resolve.

    But if example.com was actually hosted on that server how will this work? I mean if the domain itself example.com is not working I suppose ns1 and ns2 will not work as well unless its the registrar resolving it. So that is my question. Its like a cicle around. If server that has DNS server 1 hosts that domain crashes, DNS 2 will still be up but the domain itself will not be resolving. PLease guys. I need to set up this straight and I have a deadline.
    Name servers are required for a domain at the registrar end else your domain will not work. The name servers has to be registered, just like you register a domain name before using it. You need to assign the server IPs while registering the name servers and then have to assign them in the registrar domain panel itself.

    The DNS servers where the name servers are pointing to should have an A record of the domain i.e. the servers IP where the website is actually hosted.

    Now suppose, your ns1 and ns2 are on the same server, and if the server goes down, the site won't work though the server on which the site is hosted is online.
    OR
    suppose, ns1 and the website is on the same server and it goes offline, the ns2 will be of no use.

    Hope this may have cleared things for you.
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  4. #4
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    Hi, i dont think you understanded my question. The title should be "Who resolves, not How resolves"

    That means, im not talking about how a domain resolves, but who resolves the childnames, the dns server, or the registrar.

    Let me put this example on another approach to see if its more clear.

    example.com is on Server 1.
    Dns server A is on Server 1.
    Dns server B is on Server 2.

    example2.com uses ns1.example.com and ns2.example.com as dns names.

    On the registrar you have the childnames correctly setup for example.com, on Server 1, the DNs server master is setup correctly. On server 2, slave DNs is setup.


    Now, lets put Server 1 on fire. Will example2.com still resolve or not?

    You see what I mean? If example.com is not resolving, how is suppose to resolve ns1 and ns2 names, unless its the registrar with the IPs you gave him that does this. I hope that makes it clear

  5. #5
    Hi, i dont think you understanded my question. The title should be "Who resolves, not How resolves"

    That means, im not talking about how a domain resolves, but who resolves the childnames, the dns server, or the registrar.

    Let me put this example on another approach to see if its more clear.

    example.com is on Server 1.
    Dns server A is on Server 1.
    Dns server B is on Server 2.

    example2.com uses ns1.example.com and ns2.example.com as dns names.

    On the registrar you have the childnames correctly setup for example.com, on Server 1, the DNs server master is setup correctly. On server 2, slave DNs is setup.


    Now, lets put Server 1 on fire. Will example2.com still resolve or not?

    You see what I mean? If example.com is not resolving, how is suppose to resolve ns1 and ns2 names, unless its the registrar with the IPs you gave him that does this. I hope that makes it clear
    It is the registrar with the ips you provide that does the resolving. So even if example.com is down, ns1.example.com will still resolve and point to server2 because the ip for ns2.example.com is set at the registrar level.

  6. #6
    Here is how it works, you can apply it to your situation as required.

    If the name servers assigned to the domain are within the same parent tld, or a tld served by the same parent servers, the parent servers will return as part of the referral, the name server names, and the ip addresses in the form of glue records.

    This is the most efficient form of referral. In some cases, the glue records are not returned. This requires that additional queries to be performed to finally get to the right server to ask the original question. This will happen where the parent server has no knowledge of the name server other than the delegation. For example, a .org domain using .com name servers. Some parent servers never return glue records and additional queries are always required. For more information search for the terms: "dns traversal" or "dns query resolution". Add a few keywords, like tld, parent, glue to narrow your results to something worthwhile reading.

    In the case of example.com where you want to use ns1.example.com and ns2.example.com as the name servers, then what you do is:

    Insert two A records in your dns servers for ns1.example.com and ns2.example.com

    Insert two NS records in your dns servers for ns1.example.com and ns2.example.com

    Insert one SOA record in your dns servers for example.com pointing at your choice of ns1.example.com or ns2.example.com

    *after* you have done the above,

    Register ns1.example.com and ns2.example.com as name servers at the registrar.

    Assign ns1.example.com and ns2.example.com as the name servers for example.com at the registrar.

    The information above is passed on by the registrar to the registry running the parent name servers.

    Subsequent to performing all of the above steps, the parent name servers, when queried for any record ending in example.com. will be able to refer the query to the name servers ns1.example.com and ns2.example.com by returning a referral that includes the glue records.

    If you then register second.com, and want to use ns1.example.com and ns2.example.com, then you still need the two NS records pointed at ns1.example.com and ns2.example.com and a SOA record pointed at either one. But, you do not need the A records, because they are not part of second.com, nor do you register additional name servers.

    At the registrar, you would assign ns1.example.com and ns2.example.com as the name servers for second.com, but you do not create additional name servers.

    It has become common in recent years for every domain to have their own name servers. This is not necessarily the most efficient way to do things. It is far better to create one set of name servers and use them for all your domains.
    edgedirector.com
    managed dns global failover and load balance (gslb)
    exactstate.com
    uptime report for webhostingtalk.com

  7. #7
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    Quote Originally Posted by senetpro View Post
    It is the registrar with the ips you provide that does the resolving. So even if example.com is down, ns1.example.com will still resolve and point to server2 because the ip for ns2.example.com is set at the registrar level.
    So it its the registrar with the IP, why is there a need to setup it again on a nameserver with ns records and A records?

    Just for testing i created a chilname on a domain that is not activated anywhere and the ns1 record doesnt work, that means it still has to be configured in a dns server to work.

  8. #8
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    Quote Originally Posted by plumsauce View Post
    Here is how it works, you can apply it to your situation as required.

    If the name servers assigned to the domain are within the same parent tld, or a tld served by the same parent servers, the parent servers will return as part of the referral, the name server names, and the ip addresses in the form of glue records.

    This is the most efficient form of referral. In some cases, the glue records are not returned. This requires that additional queries to be performed to finally get to the right server to ask the original question. This will happen where the parent server has no knowledge of the name server other than the delegation. For example, a .org domain using .com name servers. Some parent servers never return glue records and additional queries are always required. For more information search for the terms: "dns traversal" or "dns query resolution". Add a few keywords, like tld, parent, glue to narrow your results to something worthwhile reading.

    In the case of example.com where you want to use ns1.example.com and ns2.example.com as the name servers, then what you do is:

    Insert two A records in your dns servers for ns1.example.com and ns2.example.com

    Insert two NS records in your dns servers for ns1.example.com and ns2.example.com

    Insert one SOA record in your dns servers for example.com pointing at your choice of ns1.example.com or ns2.example.com

    *after* you have done the above,

    Register ns1.example.com and ns2.example.com as name servers at the registrar.

    Assign ns1.example.com and ns2.example.com as the name servers for example.com at the registrar.

    The information above is passed on by the registrar to the registry running the parent name servers.

    Subsequent to performing all of the above steps, the parent name servers, when queried for any record ending in example.com. will be able to refer the query to the name servers ns1.example.com and ns2.example.com by returning a referral that includes the glue records.

    If you then register second.com, and want to use ns1.example.com and ns2.example.com, then you still need the two NS records pointed at ns1.example.com and ns2.example.com and a SOA record pointed at either one. But, you do not need the A records, because they are not part of second.com, nor do you register additional name servers.

    At the registrar, you would assign ns1.example.com and ns2.example.com as the name servers for second.com, but you do not create additional name servers.

    It has become common in recent years for every domain to have their own name servers. This is not necessarily the most efficient way to do things. It is far better to create one set of name servers and use them for all your domains.
    thanks your your explanation. Yes my intention is no to use each domain with his own server, but just have 1 dns server that is reliable to failures. I was just afraid the single domain that is uses as names could be the single point if failure, such if that domain itself is not resolving, that any other dns name would work. Lets say you have 30 dns servers with that domain, like ns1, ns2, ns10, ns20, etc until ns30. Each one pointing to a DNS server itself whih of course is on a separated dns server.

    I was afraid that if the domain that is used for those, example.com in case it fails to resolve would basically kill the resolution of all ns names.

    Since if a domain is using for example ns10.example.com

    It first queries example.com, then ns10, and ns10 point is to the right IP, that IP is a DNS server, and then the DNS server points to the final IP to which resolve that website. But imagine is example.com, where its physical hosted fails.

    Someome said it would be the registrar resolving each nsXX.example.com name with the IPs.

  9. #9
    Quote Originally Posted by nibb View Post
    Someome said it would be the registrar resolving each nsXX.example.com name with the IPs.
    It is not the *registrar* but the *registry* who runs the parent name servers. Two separate entities.

    And yes, nsXX.example.com is returned in the glue records for someotherdomain.com as long as nsXX.example.com is registered as a nameserver for someotherdomain.com and has been created as a nameserver itself.

    How to avoid problems with resolving example.com:

    pay for it for 10 years, lock it.
    edgedirector.com
    managed dns global failover and load balance (gslb)
    exactstate.com
    uptime report for webhostingtalk.com

  10. #10
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    Quote Originally Posted by plumsauce View Post
    It is not the *registrar* but the *registry* who runs the parent name servers. Two separate entities.

    And yes, nsXX.example.com is returned in the glue records for someotherdomain.com as long as nsXX.example.com is registered as a nameserver for someotherdomain.com and has been created as a nameserver itself.

    How to avoid problems with resolving example.com:

    pay for it for 10 years, lock it.
    Ah yes, registry, Verisign in that case. If it was the registrar then i think we would have major outages, but its just 1 company for all .com domains, Verisign.

    Thanks for your suggestion but is that exaclty what happened. I forget to renew a domain and it only was expired for 1 hour but the whole DNS had an outage and im think im receiving my last check this month. It was a stupid mystake but my boss if has become a devil since then and i want to come with a solution to save my 10 year job. I though everything was ok until that happen and now im not sure how save it is anymore. So i suppose im save, since only if Verisign has an outage it would be a problem but then again the whole internet would be affected. So why do you still have to register the name servers on the bind itself if Verisign has already the names to IP data that was passed from the Registrar. I assume its also not safe then use other names which are not TLD for servers, since you depend on the registry, example, country level domains.

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