DNS stands for the Domain Name System, a hierarchical, distributed database where the keys are domain names.

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What are SPF records, and how do I configure them?

This is a canonical question about setting up SPF records. I have an office with many computers that share a single external ip (I'm unsure if the address is static or dynamic). Each computer ...
18
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7answers
12k views

How to use DNS/Hostnames or Other ways to resolve to a specific IP:Port

This is a Canonical Question 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 ...
46
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3answers
16k views

What is a glue record?

This is a Canonical Question about DNS glue records. What exactly (but briefly) is a DNS glue record? Why are they needed and how do they work?
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2answers
77k views

How to Configure Windows Machine to Allow File Sharing with DNS Alias

What process is necessary to configure a Windows environement to allow me to use DNS CNAME to reference servers? I want to do this so that I can name my servers something like SRV001, but still have ...
33
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4answers
2k views

Why does DNS work the way it does?

This is a Canonical Question 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. ...
68
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6answers
58k views

Setting the hostname: FQDN or short name?

I've noticed that the "preferred" method of setting the system hostname is fundamentally different between Red Hat/CentOS and Debian/Ubuntu systems. CentOS documentation and the RHEL deployment guide ...
104
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15answers
84k views

Why is DNS failover not recommended?

From reading, it seems like DNS failover is not recommended just because DNS wasn't designed for it. But if you have two webservers on different subnets hosting redundant content, what other methods ...
52
votes
20answers
21k views

Should we host our own nameservers?

I currently have my ISP providing DNS for my domain, but they impose limitations on adding records. Therefore, I am thinking about running my own DNS. Do you prefer to host your own DNS, or is it ...
54
votes
14answers
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Top level domain for private networks?

On our office network we have an internal DNS and all the hostnames are whatever.lan. On my VMware VMs, on their host-only network I call them whatever.vm. We now have a private IP space network in ...
13
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3answers
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What should the order of DNS servers be for an AD Domain Controller and Why?

This is a Canonical Question about Active Directory DNS Settings. Related: What is Active Directory and how does it work? Assuming an environment with multiple domain controllers ...
13
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4answers
8k views

Set root domain record to be a CNAME

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 ...
8
votes
1answer
4k views

In DNS can an IN NS point to a CNAME?

Is it allowed to have an NS record be a CNAME? E.g.: subdomain.example.com. IN NS ns1.example.com. ns1.example.com. CNAME foo.example.com. foo.example.com. IN A ...
38
votes
1answer
35k views

How long does it take for DNS records to propagate?

This is a Canonical Question about DNS Propagation How long does it take for an the various types of records to propagate? Do some propagate faster than others? Why does it take time for DNS ...
50
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15answers
7k views

Are IP addresses “trivial to forge”?

I was reading through some of the notes on Google's new public DNS service: Performance Benefits Security Benefits I noticed under the security section this paragraph: Until a standard ...
23
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5answers
14k views

Geo-DNS providers? [closed]

We've got a website visited by users mainly in the USA and UK. The site will be run on servers in both these locations. We would like to use a DNS service to direct users to the nearest server, but ...
33
votes
23answers
5k views

Who is a good registrar these days? [closed]

It's been a long time since I've had to register a new domain. What registrar is considered geek and sysadmin friendly? I've heard that godaddy will screw you 10 ways to Sunday, and a lot of the ...
4
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5answers
5k views

How can I automaticaly change the DNS A record to point my site to a secondary server in case of a failure?

My hosting is charging me a $50/month fee to put my servers on the same VLAN so that I create a cluster using the Network Load Balancing feature. I'm really not needing split the load between the ...
51
votes
11answers
14k views

Multiple data centers and HTTP traffic: DNS Round Robin is the ONLY way to assure instant fail-over?

Multiple A records pointing to the same domain seem to be used almost exclusively to implement DNS Round Robin as a cheap load balancing technique. The usual warning against DNS RR is that it is not ...
30
votes
16answers
28k views

Is Round-Robin DNS “good enough” for load balancing static content?

We have a set of shared, static content that we serve up between our websites at http://sstatic.net. Unfortunately, this content is not currently load balanced at all -- it's served from a single ...
44
votes
8answers
42k views

Is a wildcard CNAME DNS record valid?

I know it's valid to have a DNS A record that's a wildcard (e.g. *.mysite.com). Is it possible/valid/advised to have a wildcard CNAME record?
25
votes
8answers
21k views

Private IP address in public DNS

We have an SMTP only mail server behind a firewall which will have a public A record of mail.. The only way to access this mail server is from another server behind the same firewall. We do not run ...
30
votes
2answers
7k views

Why does Heroku warn against “naked” domain names?

I ran across this page in the Heroku docs... Naked domains, also called bare or apex domains, are configured in DNS via A-records and have serious availability implications when used in highly ...
8
votes
1answer
256 views

Why can't a CNAME record be used at the apex of a domain?

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 ...
10
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3answers
1k views

Apache: Scammers point dozens of domain names at my dedicated IP. How to prevent this?

For the sake of discussion, pretend that I have an Apache webserver which serves a website at www.example.org. This domain name resolves to the public IP address at 192.168.1.100 (pretend this is a ...
21
votes
5answers
6k views

CNAME for top of domain?

Is it possible to set a CNAME record at the top of a domain? (i.e. @ CNAME www, @ CNAME foobar.com., etc.) My ISP says that it's only possible to use CNAME's for subdomains but I've read somewhere ...
15
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2answers
3k views

Is dig +trace always accurate?

When the accuracy of a DNS cache is in question, dig +trace tends to be the recommended way of determining the authoritative answer for an internet facing DNS record. This seems to be particularly ...
4
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5answers
3k views

How do I move my website to a new server without interruption to email?

I have a corporate website on a server that also hosts all our email. I have no idea how diligent all the employees have been about backing up their email / leaving old messages on the server, etc. In ...
55
votes
22answers
9k views

How the heck is http://to./ a valid domain name?

Apparently it's a URL shortener. It resolves just fine in Chrome and Firefox. How is this a valid top-level domain? Update: for the people saying it's browser shenanigans, why is it that: ...
17
votes
8answers
20k views

Overriding some DNS entries in BIND for internal networks

I have an internal network with a DNS server running BIND, connected to the internet through a single gateway. My domain "example.com" is managed by an external DNS provider. Some of the entries in ...
18
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4answers
10k views

Reverse DNS in a CIDR world

Reverse DNS seems to be strongly tied to class boundaries, what methods exist now that CIDR is the standard to delegate authority for a subnet? If multiple methods exist which one is best? Do you ...
5
votes
10answers
856 views

Is there a good overview of the DNS system?

I want to get an understanding of how the DNS system works. How domain names actually get resolved and how admins setup a domain name so it is resolved correctly to a target machine. The sources you ...
10
votes
13answers
9k views

Using .local for internal websites [duplicate]

Is it okay to use app.mycoolname.local for URLs that are private / internal? We have several applications that are web based, but they are private apps and are not exposed to the public. We have ...
3
votes
4answers
2k views

What is the correct behaviour when Nameservers Change

I have been having some issues with a certain network supplier over unchanged nameservers making my site invisible to their customers. I wouldnt be bothered except that they are one of the largest ...
6
votes
5answers
5k views

Active Directory: Is it required that the “A” record for a domain point to a Domain Controller?

Currently we have an Active Directory setup, and say the name is 'domain.com'. The DNS entries for domain.com has two A records pointing to the two domain controllers. I would like internal users to ...
5
votes
2answers
3k views

How browsers handle multiple IPs

Can someone direct me to information on exact browsers behavior when browser gets multiple A records for a given hostname (say ip1 and ip2), and one of them is not accessible. I interested in EXACT ...
8
votes
5answers
12k views

How do I configure SPF for multiple domains on a server? (also allowing gmail as a sender)

SPF (Sender Policy Framework) seems like a good way to combat spammers/spoofing. However, despite reading the explanations several times, I'm not quite understanding how to configure it correctly. ...
15
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3answers
2k views

Naming a new Active Directory forest - why is split-horizon DNS not recommended?

Hopefully, we all know what the recommendations for naming an Active Directory forest are, and they're pretty simple. Namely, it can be summed up in a single sentence. Use a subdomain of an ...
8
votes
6answers
11k views

When is a secondary nameserver hit?

Take this scenario: domain: foobar.com ns1: 2.2.2.2 ns2: 3.3.3.3 My question: Is ns2 hit just in the event that ns1 is down? Or, is ns2 hit any time that ns1 returns a miss/doesn't resolve ...
4
votes
2answers
8k views

How does ServerName and ServerAlias work?

It's the following part of a virtual host config that I need further clarification on: <VirtualHost *:80> # Admin email, Server Name (domain name), and any aliases ServerAdmin ...
10
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4answers
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How to create a CNAME for a domain's root name

I'd like to set a domain's root name to a CNAME instead of the usual A record. Here's a perfect example of what I'm trying to do: dig lrnskls.com Notice the answer section: ;; ANSWER SECTION: ...
8
votes
5answers
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Reverse DNS - how to correctly configure for SMTP delivery

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, ...
10
votes
3answers
6k views

Wildcard DNS and subdomains

Let'say that i've got the domain mydomain.com. I want that when any visitor goes to www.mydomain.com xyz.mydomain.com abc.mydomain.com asd.mydomain.com qwe.mydomain.com etc... the visitor will ...
4
votes
8answers
12k views

Why should one have a secondary DNS server?

I'm very confused. I basically understand how DNS works. Here's an example that helps illustrate what I'm having trouble understanding. Right now, I run a small web-server. I use my provider's DNS ...
7
votes
6answers
702 views

how a dns query works [closed]

when i type www.google.com how does the dns lookup work. According to my knowledge it first goes to the root server and finds out where the .com dns server is. Next it returns the ip address of that ...
4
votes
2answers
536 views

What is the canonical name for domain names with extra parts?

I am confused about domain names (I think) I call these things, i.e. names you can buy, 'domain names' bbc.co.uk google.com I call these things, i.e. extensions of names 'host names' ...
3
votes
5answers
2k views

Enable access without “www.” on Ubuntu

I want to enable the access to my site without the "www." prefix. I tried to insert this in my /etc/apache2/sites-available file: <VirtualHost *:80> serverName mydomain.gov.br ...
3
votes
3answers
273 views

Website hosting from home - IIS6

I'm wanting to host a few websites from home, primarily because I'm using some BETA Microsoft software (.NET 4 and EF) and don't want to install it on my production server which is hosted at ...
2
votes
3answers
6k views

Configure DNS server to return same IP for all domains

I would like to configure a nameserver that will return the same IP address ("A" record) for any arbitrary host name. For example: example.com subdomain.example.com someotherdomain.com ...
3
votes
1answer
177 views

My visitors %20 percent can't reachable to my web site

i have dedicated web server and also i hosting www.btgmaslak.com web site. I'm facing a problem about 1 days. My visitors about 20 percent can't reach my web site. I thing this problem occurs because ...
2
votes
1answer
577 views

No-ip works for non-internal clients, pinging works internally

I'm having a really bizarre problem while using No-IP. I can access the server fine from clients not on the local network and local and remote clients can ping the server just fine. I get the same ...