I am trying to build my own DNS. I have one server which I would like to use as DNS server.   Why, according to RFC2182 section 5 () I must have TWO servers (3 recommended)?   I tried creating ns1.example.com and ns2.example.com pointing to same IP and it works for some TLDs fine but for my .us domain it doesn't open the website.   Why some TLDs does not work with just one server (two ns pointing to same IP)?   Sorry if the quiestion is boring. Thanks!
56504
This is a  about DNS geo-redundancy.   It's extremely common knowledge that geo-redundant DNS servers located at separate physical locations are highly desirable when providing resilient web services. This is covered in-depth by document , but some of the most frequently mentioned reasons include:   Protection against datacenter disasters. Earthquakes happen. Fires happen in racks and take out nearby servers and network equipment. Multiple DNS servers won't do you much good if physical problems at the datacenter knock out both DNS servers at once, even if they're not in the same row. Protection against upstream peer problems. Multiple DNS servers won't prevent problems if a shared upstream network peer takes a dirt nap. Whether the upstream problem completely takes you offline, or simply isolates all of your DNS servers from a fraction of your userbase, the end result is that people can't access your domain even if the services themselves are located in a completely different datacenter.   That's all well and good, but are redundant DNS servers really necessary if I'm running all of my services off of the same IP address? I can't see how having a second DNS server would provide me any benefit if no one can get to anything provided by my domain anyway.  I understand that this is considered a best practice, but this really seems pointless!
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I am running multiple web servers in my house, each of which is plugged into my router.  Server A Server B Server C  I currently can only use one server since my IP (xx.xxx.xx.xx) port 80 is pointing towards server A. However some domains point to server A, some to B, etc.  With my one IP address, how do I point to each server? For example my A(host) records all point to just my IP address.  Sorry if I sound confusing. Let me know if I am not being clear.  Each server is running Ubuntu Server 12.04.02 and is using Apache (if that helps). My router is also a Netgear and my ISP is Time Warner Cable.
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So, I'm running an Apache server on CentOS 7. I have two domains pointing to the same place:  and . In my cfg, I have three VirtualHosts; one for http (for both) one for the subdomain-less, and one for the www. I have the separate certs configured (one for each), but when I deploy, Apache just serves up the first cert it finds in the cfg. So if I have the VirtualHost for www first, it serves up the www cert for both  and   I have other domains being served on the same box and they get all the right certs.  Can somebody please explain what is going on here? It's driving me absolutely   # Abbreviated Main config file for example.com domain &lt;VirtualHost *:80&gt;    ServerAlias example.com   ServerAlias www.example.com    DocumentRoot "/var/www/example.com"  &lt;/VirtualHost&gt;  &lt;VirtualHost *:443&gt;   ServerAlias example.com      DocumentRoot "/var/www/example.com"    SSLEngine on   SSLCertificateFile "/etc/letsencrypt/live/example.com/fullchain.pem"   SSLCertificateKeyFile "/etc/letsencrypt/live/example.com/privkey.pem"  &lt;/VirtualHost&gt;  &lt;VirtualHost *:443&gt;   ServerAlias www.example.com    DocumentRoot "/var/www/example.com"    SSLEngine on   SSLCertificateFile "/etc/letsencrypt/live/www.example.com/fullchain.pem"   SSLCertificateKeyFile "/etc/letsencrypt/live/www.example.com/privkey.pem"  &lt;/VirtualHost&gt;
63541
we have an godaddy account for dns, and we registered our servers in godaddy dns admin console, right now we have an problem, our case is our registered server ip in godaddy dns can able to register  any one of other dns service providers, it might be an issue, someone can easily able to register subdomains to our server ip easily.For eg: if some one have to register subdomain in the name of porn sites and those subdoamins it's pointing to our servers directly it would be an issue for us.How to avoid this case.Please can anyone help for this problem.
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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.
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This is a  about CNAMEs at the apices (or roots) of zones   It's relatively common knowledge that CNAME records at the apex of a domain are a taboo practice.  Example: example.com. IN CNAME ithurts.example.net.  In a best case scenario nameserver software might refuse to load the configuration, and in the worst case it might accept this configuration and invalidate the configuration for example.com.  Recently I had a webhosting company pass instructions to a business unit that we needed to CNAME the apex of our domain to a new record. Knowing that this would be a suicide config when fed to BIND, I advised them that we would not be able to comply and that this was bunk advice in general. The webhosting company took the stance that it is not outright forbidden by standard defining RFCs and that their software supports it. If we could not CNAME the apex, their advice was to have no apex record at all and they would not provide a redirecting webserver. ...What?  Most of us know that  insists that A CNAME record is not allowed to coexist with any other data., but let's be honest with ourselves here, that RFC is only Informational. The closest I know to verbiage that forbids the practice is from :     If a CNAME RR is present at a node, no other data should be   present; this ensures that the data for a canonical name and its aliases   cannot be different.   Unfortunately I've been in the industry long enough to know that "should not" is not the same as "must not", and that's enough rope for most software designers to hang themselves with. Knowing that anything short of a concise link to a slam dunk would be a waste of my time, I ended up letting the company get away with a scolding for recommending configurations that could break commonly used software without proper disclosure.  This brings us to the Q&amp;A. For once I'd like us to get really technical about the insanity of apex CNAMEs, and not skirt around the issue like we usually do when someone posts on the subject.  is off limits, as are any other Informational RFC applicable here that I didn't think of. Let's shut this baby down.
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This is a  about hostname-awareness and proxying.   I know that some protocols are hostname-aware; that is, when I connect to the HTTP server at www.example.com it knows I want www.example.com's HTTP service, not www.example.net's, even though they are on the same IP address.  How can I do this for protocol foo?  (Temporary note: this question appears pursuant to .)
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I am planning to have my own website and would like to ask some questions regarding about the organization (I don't know if this is the right term for it) of domain names.  Let me give an example:  If I have a domain named “www.joe.com” but is planning to have different websites or categories for my varied interests but would still retain the  “joe” name on my domain, would it be better to have a sub-domain instead?  Is that it?  Is this what would turn out:  www.joe.com             = my main site bookworm.joe.com        = a blog for my love of books travel.joe.com          = a blog for my travel experience food.joe.com            = a blog for my love of food and cuisine  I also notice that there are other websites that are like this: (this is just an example, but you get the idea)  www.personname.com          = main site www.personname.com/blog     = a blog for his site ( is this a subdomain now)  Everytime you go to the www.personname.com, you are then redirected to the www.personname.com/blog address.  Is it safe to say that the blog address is a sub-domain and for blogging only and then the www.personname.com is the main site?  What is the difference of this approach compared to the first example I've given above?  Cheers!
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$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?
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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?
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Greetings all,  I have a server with two tomcat services (one being run on port 80, the other 8080).   What I'm wanting to achieve is to have two different DNS records for these two ports, so they'll be accessible via:  http://example1/ http://example2/   Instead of  http://example1/ http://example1:8080/   I know this isn't possible using DNS A records, but does anyone know of another solution I could look into?  Thanks,  Andrew
15994
This is a  about DNS/Hostnames resolution to IPs/Ports   Example 1  I'm running a web server on port 80 and another on port 87. I would like to use DNS so that www.example.com goes to port 87. How can I accomplish this using DNS only?  Example 2  I'm running a service on my server on a non-standard port. How can I get clients to connect to this non-standard port automatically? Can I use DNS? Is there some application specific support where DNS could indicate the IP and Port?   Example 3  Do some application protocols specifically support hostname awareness, and allow special actions to be taken based on this information? Are there other questions on Server Fault that cover some of these?  Commandeering: This question was originally asking about running IIS and Apache on the same server, but the same concepts can be applied to any server software receiving connections from clients. The Answers below describe the technical problems and solutions of using DNS and application protocol support to assign a port number for a client to connect.
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if I set x.domain.com and y.domain.com to the same ip address, Does it mean Nginx couldn't tell the differences between x.domain.com and y.domain.com?  Is it impossible to map x.domain.com and y.domain in the server directive in the server context to the different folder?  I also want to learn more about how the computer network work? Anyone could give me some resources?
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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?
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My PC is behind a NAT router that has a public IP address. If I want to host a website then I believe I need a domain name which I can purchase from some site which would pledge to resolve all DNS requests for that domain name and send the IP address of my NAT router (assuming I do not want to host my domain name on their servers). Now I want to host a web server on my computer.   What changes should be done to the NAT router's configuration to forward all HTTP requests for example.com to my PC in the internal network. Is the above strategy correct? Is it commonly used?
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Does anyone have a regular expression handy that will match any legal DNS hostname or IP address?  It's easy to write one that works 95% of the time, but I'm hoping to get something that's well tested to exactly match the latest RFC specs for DNS hostnames.
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My web server (Ubuntu, Nginx) have both IPv4 and IPv6 addresses assigned by the host. For my website, shall I bind it to only an IPv6 address? Is it the standard recommended way? Or, shall I use both IPv4 and IPv6 addresses?