For example, lets say there is a hosting company, hostingcompany.com, with nameserver ns1.hostingcompany.com.  When I type hostingcompany.com into my browser, my computer contacts a top level .com domain nameserver, which in turn contacts the name server for hostingcompany.com to get the A record for hostingcompany.com or any of its subdomains.  Isn't this circular, since the FQDN for the nameserver is a subdomain of the domain name itself?  In other words, in order to find the IP address of ns1.hostingcompany.com, we need a nameserver for *.hostingcompany.com, which is itself?  What am I missing?
88517
This is a  about DNS (Domain Name Service).   If my understanding of the DNS system is correct, the .com registry holds a table that maps domains (www.example.com) to DNS servers.   What is the advantage? Why not map directly to an IP address? If the only record that needs to change when I am configuring a DNS server to point to a different IP address, is located at the DNS server, why isn't the process instant? If the only reason for the delay are DNS caches, is it possible to bypass them, so I can see what is happening in real time?
78106
I'm attempting to figure out an error message that I got from dnsstuff.com when examining my DNS records.  The error reads as follows.     NS list does not match list from parent zone. This should be addressed because queries for this domain may require an extra lookup (and more overhead) because there is no direct relationship between the NS records at the parent and the NS records at the authoritative servers. This can cause delays. The mismatched NS list is:      nameserver ns1.domain.co. | xxx.xx.xxx.xxx is missing NS2.domain.co. | yy.yyy.yy.yyy   There are a couple questions I have regarding this.   What is the difference between a parent and authoritative zone?  In other forum posts I've seen, the seem to be used interchangeably (although that could be my misperception). What does it mean for the NS list not to match the list from the parent zone?  What is "the list from the parent zone" to which they refer? How might you recommend that I resolve this?   In case this affects any answers, I'm running Virtualmin on Ubuntu 12.04.  Any help is appreciated.  Many thanks in advance!
98240
My isp provides a dns service; but unfortunately they do block certain sites. I would like to use opendns or google; but it seems like it doesn't work.    I have set up a wired connection; given a manual ip and entered opendns-ip's in the nameserver field (all through the gui). Still url's are being resolved through my ISP. I have tried to configure the same on my girlfriends laptop (win 7) and I also can't seem to do the setup. My previous computer also was a win 7 and had no problem. (so I believe the problem is 'me') If it were only one site, i could edit the hosts file; but I prefere to circumvent their whole dns server.  Is there something an isp can do to block the use of other dns-servers than theirs? Is it possible to re-route the ISP dns to the opendns?
15666
This is a  about Active Directory DNS Settings. Related:     Assuming an environment with multiple domain controllers (assume that they all run DNS as well):  in what order should the DNS servers be listed in the network adapters for each domain controller? Should 127.0.0.1 be used as the primary DNS server for each domain controller? Does it make any difference, if so what versions are affected and how?
101368
I've used IRC for a long time and I've seen people with really unique hostnames. I'm wondering how they are able to have those?  My theory is that one sets up a server as part of the efnet/freenode network and somehow masks his real identity behind that custom server.  Could someone explain layman's terms how this is done?  And on a related note, how easy is it to customize your hostname if you're say, running an irc client on your domain and would like to use your domain name instead of the internal vps address?   Example: if I'm using linode, it'll say I'm member_whatever@members.linode.com as my hostname. I host several sites so I'm pointing a few A records to my server, I want my hostname to be something like 'meder@medero.org' for example, instead of the default linode one.
27562
It's the following part of a virtual host config that I need further clarification on:  &lt;VirtualHost *:80&gt;   # Admin email, Server Name (domain name), and any aliases   ServerAdmin example@example.com   ServerName  141.29.495.999   ServerAlias example.com ...   This is and example config, similar to what I currently have (I don't have a domain name at the moment).  &lt;VirtualHost *:80&gt; - Allow the following settings for all HTTP requests made on port 80 to IPs that this server can be contacted on. For instance, if the server could be accessed on more than one IP, you could restrict this directive to just one instead of both.  ServerName - If the host part of the HTTP request matches this name, then allow the request. Normally this would be a domain name that maps to an IP, but in this case the HTTP request host must match this IP.  ServerAlias - Alternate names accepted by the server.  The confusing part for me is, in the above scenario, if I set ServerAlias mytestname.com and then made an HTTP request to mytestname.com, there would have to be a DNS record pointing to the server's IP for this to work? In which case, is ServerAlias just basically EXTRA ServerName entries?  Say I had a DNS entry such that foobar.com = 141.29.495.999 but then I had ServerName = 141.29.495.999 and ServerAlias was empty, would that mean that although foobar.com gets resolved to the right IP, because there is no reference to accept foobar.com in ServerName or ServerAlias?  Or something. Man I'm confused.
101853
I recently received the following message from Google Webmaster Tools:     Dear site owner or webmaster of ,      [...]      Below are one or more example URLs on your site which may be part of a   phishing attack:            [...]   What I don't understand is that I never had a subdomain repair.gotgenes.com, but visiting it in the web browser gives an actual  My DNS is , which does not list a repair subdomain. My domain name is registered with GoDaddy, and the nameservers are correctly set to NS1.AFRAID.ORG, NS2.AFRAID.ORG, NS3.AFRAID.ORG, and NS4.AFRAID.ORG.  I have the following questions:   Where is repair.gotgenes.com actually registered? How was it registered? What action can I take to have it removed from DNSs? How can I prevent this from happening in the future?   This is pretty disconcerting; I feel like my domain has been hijacked. Any help would be much appreciated.
43060
I have a problem in which I cannot access a server using its public name from the same network as the server. Access to the server works fine from the internet.  Reading up on this problem, I've ran across such things as hairpin NAT, loopback NAT, split DNS, editing hosts files, etc.  My network has a SMC 8013WG-CCR (Comcast) cable modem connected to a Linksys WRT54G2. As I understand, the router is supposed to handle this sort of loopback (by leaving the security option "Filter Internet NAT Redirection" disabled), but the connection between these two devices is a secondary LAN, so I don't think the router "knows" what the proper public IP address is.  The easiest solution would be to edit the hosts files of all the computers in the network, but many are notebook computers which will need to access the server both on the LAN and externally.  The server is Windows Server 2012, so I could set it up as the internal DNS server but I don't have enough experience with this to really understand how it would interact with the router, DHCP, etc.  I am prepared to purchase a new router if I need something with greater capability. It appears from my research that most IT admins prefer to solve this problem with split DNS rather than hairpin NAT. I understand the concept of hairpin NAT more clearly than split DNS. It seems to me that the router just needs to provide LAN clients with the local IP of the server when clients use the public name (sub.domain.com). Isn't that just an entry in a local DNS cache? Is that what split DNS does?  What would be a good solution to implement this fix for a small business?
58087
I started a new service and we need to send emails to our customers (new account confirms, etc).   My server is known as prod01.bidrodeo.com and resolves to 97.107.134.38 .  For reverse DNS, 97.107.134.38 resolves to prod01.bidrodeo.com . However, all our email addresses are in the form of user@bidrodeo.com. Should I make the reverse DNS point to bidrodeo.com instead?   My emails are getting delayed or rejected by certain systems and i am not sure if my reverse DNS is not set up correctly.
74822
I want to find out all the subdomains of a given domain. I found a hint which tells me to dig the authoritative Nameserver with the following option:  dig @ns1.foo.bar some_domain.com axfr   But this never works. Has anyone a better idea/approach
57475
If we have example.com we would setup things something like this: $ORIGIN example.com. @  1D  IN  SOA ns1.example.com. hostmaster.example.com. (                   2002022401 ; serial                   3H ; refresh                   15 ; retry                   1w ; expire                   3h ; nxdomain ttl                  )           IN  NS     ns1.example.com.           IN  NS     ns2.example.com.  since in the parent zone .com. there is already NS record for the example.com. child zone and A glue record for the ns1.example.com. for what purpose do we state NS records again in the child zone? and also, do we need to state A record for the name servers in the child zone itself?
16559
Is it allowed in DNS to have a CNAME record that points to another CNAME record?  The reason we need this is that we have a hostname that we want to be looked up to the IP address of our web server computer. We also have another web server computer stand by that could be activated in case the first one would die. In such a case we would quickly need to point the hostname to the IP address of the stand by web server computer.  Unfortunately the hostname resides in a DNS domain where any change would take long time due to manual operation dependent on other sysadmins. But we have another DNS domain where we can perform the changes ourselves quickly. Having CNAME to CNAME chain seems like a possible solution. But is it allowed? Will web browsers understand it?
61998
We have a custom java web app. We are setting it up in instances in different vps (different providers, different locations). We have for example:  Instance 1: http://server1/app1 Instance 2: http://server1/app2 Instance 3: http://server2/app3   Each instance is independent and self contained. We have several docens of this instances and will continue to add them.   My question is regarding the dns managment, as we want to map different subdomains to the instances.   client1.mypp.com  &gt; http://server1/app1 client2.mypp.com  &gt; http://server1/app2 client3.mypp.com  &gt; http://server2/app3  clientN.mypp.com  &gt; http://anyserver/appN   Right now we are adding the A records manually to the DNS records to relate subdomain to the ip. We will develop some code to do it using the API of the DNS provider.   Is this the most appropiate aproach? Should we use some kind of proxy instead? We expect to have thousands of isntances accros different servers. I am interested in perfomance and availability.
5434
I need to create an NS record for a domain that is a CNAME, for the purpose of having two domains pointed at one IP, and not having to maintain the current IP address in two different places.  The DNS provider for this domain is DynDNS, but they block this operation:     CNAME cannot be created with label   that is equal to zone name   I can do this with another domain whose DNS is served by 1and1:  root@srv-ubuntu:~# dig myseconddomain.co.uk  ; &lt;&lt;&gt;&gt; DiG 9.4.2-P1 &lt;&lt;&gt;&gt; myseconddomain.co.uk ;; global options:  printcmd ;; Got answer: ;; -&gt;&gt;HEADER&lt;&lt;- opcode: QUERY, status: NOERROR, id: 61795 ;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0  ;; QUESTION SECTION: ;myseconddomain.co.uk.             IN      A  ;; ANSWER SECTION: myseconddomain.co.uk.      71605   IN      CNAME   myfirstdomain.co.uk. myfirstdomain.co.uk.     59      IN      A       www.xxx.yyy.zzz  ;; Query time: 298 msec ;; SERVER: 10.0.0.10#53(10.0.0.10) ;; WHEN: Tue Aug 18 14:17:26 2009 ;; MSG SIZE  rcvd: 78   Is this a breach of the RFCs or does DynDNS have a legitimate reason for blocking this action?  Followup Thanks to the two answers already posted I now know that 1and1 IS breaching RFCs to do this. However it does work and they seem to support it. For a company that hosts so many domains it seems very odd that they get away with doing this on such a massive scale without objection.  More followup  The output of "dig myseconddomain.co.uk ns" as requested.  root@srv-ubuntu:~# dig myseconddomain.co.uk ns  ; &lt;&lt;&gt;&gt; DiG 9.4.2-P1 &lt;&lt;&gt;&gt; myseconddomain.co.uk ns ;; global options:  printcmd ;; Got answer: ;; -&gt;&gt;HEADER&lt;&lt;- opcode: QUERY, status: NOERROR, id: 18085 ;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 2  ;; QUESTION SECTION: ; myseconddomain.co.uk.             IN      NS  ;; ANSWER SECTION: myseconddomain.co.uk.      4798    IN      NS      ns67.1and1.co.uk. myseconddomain.co.uk.      4798    IN      NS      ns68.1and1.co.uk.  ;; ADDITIONAL SECTION: ns67.1and1.co.uk.       78798   IN      A       195.20.224.201 ns68.1and1.co.uk.       86400   IN      A       212.227.123.89  ;; Query time: 59 msec ;; SERVER: 10.0.0.10#53(10.0.0.10) ;; WHEN: Wed Aug 19 12:54:58 2009 ;; MSG SIZE  rcvd: 111
5483
$ORIGIN example.com. ; not necessary, using this to self-document  $TTL 3600 @        IN     SOA   ns1.example.com. admin.example.com. (                       1970010100 7200 1800 1209600 300)  @        IN     NS   ns1.example.com. @        IN     NS   ns2.example.com.  @        IN     A    198.51.100.1 ns1      IN     A    198.51.100.2 ns2      IN     A    198.51.100.3  sub1     IN     NS   ns1.example.edu.  sub2     IN     NS   ns1.sub2 ns1.sub2 IN     A    203.0.113.1 ; inline glue record   The role of a NS record beneath the apex of a domain is well-understood; they exist to delegate authority for a subdomain to another nameserver. Examples of this above would include the NS records for sub1 and sub2. These allow the nameserver to hand out referrals for portions of the domain that it does not consider itself authoritative for.  The purpose of the NS records at the apex of a domain, ns1 and ns2 in this case, seem to be less understood by the internet at large. My understanding (which may not be holistic) is as follows:   They are not used by caching DNS servers in order to determine the authoritative servers for the domain. This is handled by , which is defined at the registrar level. The registrar never uses this information to generate the glue records. They  used to delegate authority for the entire domain to other nameservers. Trying to do so with software such as ISC BIND will not result in the "expected" referral behavior at all, as the nameserver will continue to consider itself authoritative for the zone. They are not used by the nameserver to determine whether it should return authoritative responses (AA flag set) or not; that behavior is defined by whether the software is told to be a master or a slave for the zone. Most nameserver software will quite happily serve apex NS records that disagree with the information contained by the upstream glue records, which will in turn cause well-known DNS validation websites to generate warnings for the domain.   With this being the case, what are we left with? Why are we defining this information if it doesn't appear to be consumed by caching DNS servers on the internet at large?
54923
If is possible to find out which nameservers a domain was previously pointing too? I need to try and find where a domain was previously hosted so that I can try and gain access to an old hosted email account.   Any ideas?
70118
My apologies if this has been asked before. I haven't found an adequate solution so... yeah.  When a specific domain, "example.com" is accessed, I want it to act normally. In other words, it should go to port 80 as expected and interact with Apache.  When a different sub-domain, "mc.example.com" is accessed, I don't want it to access the Apache web server. I want it to go interact with a different program, listening on, say, port 4096. Thus, going to "mc.example.com" would have the same/similar function as "example.com:4096". The service is Minecraft  When a third sub-domain, "vpn.example.com" is accessed, I want it to go interact with a different service, listening on, say, port 687. The service is openVPN  Is there a simple way to do this? If so, what is it? Does it involve configuring a VirtualBox in Apache (a method I tried and failed miserably. xD)? Or can it be done using ipTables? If it means anything, I am running 32-bit Centos 5.5(I believe. Its a recent version of Centos)