DNS 101A crash course in the basics of website DNS, and

what it takes to “go live.”

What is DNS?

DNS stands for “Domain Name System.”

It is one of the backbones of how the Internet works.

DNS is what tells “the Internet” where to find a specific website.

DNS is like 411

DNS ties an IP address to a domain name, just like 411 ties a person’s name to a phone number.

DNS is like 411

You: “Hello, operator? Can you connect me to Seymour Butts?”

Operator: “Sure, that number is 555-1234. Please hold and I’ll connect you.”

DNS is like 411

You: “Hello, DNS? Can you connect me to www.seymourbutts.com?”

DNS: “Sure, that IP address is 123.45.34.67. Please hold and I’ll connect you.”

How does it work?

A site owner register their domain name at a domain name Registrar. (GoDaddy.Com, etc.)

When they register, they are asked to assign the domain name at least TWO NS Records, (Name Servers).

ONLY the site owner or someone with access to the Registrar can change the NS records.

NS Records

NS Records tell “the Internet” which hosting company to send requests to.

NS Records are provided by the hosting company (Rackspace, etc.)

They usually look something like this: ns1.rackspace.com, ns2.rackspace.com

Once Name Servers are correct, we don’t need to deal with the Registrar anymore.

The Website Host

Now that “the Internet” knows which hosting company’s network to send requests to, it’s up to the hosting company’s records to narrow it down a little.

DNS Zones

A request for seymourbutts.com is sent to Rackspace because the Registrar knows the Name Servers. But Rackspace hosts a LOT of websites. DNS Zones tell “the Internet” where to go to find the website once they get to Rackspace.

DNS Zones are created on the hosting web server.

Typical Request

User types www.seymourbutts.com into their browser.

DNS looks up the Name Server on record at the registrar for www.seymourbutts.com and sends the request over to Rackspace.

Rackspace then uses the DNS Zones to figure out which IP address to send the request to.

Multiple Domains

Each domain name needs its NS Records updated at the Registrar.

Each domain name needs its own DNS Zone.

If a DNS Zone is not set up for all applicable domains, those domains WILL NOT resolve.

Multiple Domains

Be sure to ask the client if they have more than one domain name pointing to their site.

If they do, ask whether all of the domains point to the website homepage.

If different domains point to different pages, DNS Zones still need to be set up, but additional programming is required.

Trouble Brewing

If the Name Servers are incorrect at the Registrar, or if the DNS Zone is not set up correctly, the website WILL NOT resolve properly.

Externally Hosted Mail

MX (Mail Exchange) Records are part of the DNS Zone Record.

By default, it is assumed that mail is hosted locally on the web server.

If a client is hosting mail somewhere OTHER than the server hosting their website, we MUST be given correct MX information.

Externally Hosted Mail

MX information is added to the DNS Zone so that their mail will continue to work.

The MX information MUST come from the client’s IT Dept, or from the mail hosting company.

Externally Hosted Mail

If the client’s IT department doesn’t immediately know what an MX record is, YOU ARE TALKING TO THE WRONG PERSON.

Ask to speak to a representative from the company that hosts their email.

Externally Hosted Mail

If the client has multiple domains AND externally hosted email, we must clarify if all domains accept email, or if they use one primary domain for email.

Each additional domain that accepts email requires changes to the MX records in a DNS Zone. This takes time.

DNS Caching

24-48 hours (but not really).

DNS is frequently cached to speed things up. ISPs, corporate networks, computers and even browsers cache DNS.

DNS caching can result in delays in seeing changes. Restarting the computer sometimes helps.

DNS CachingA brand-new domain, or a new sub-domain (for example, http://can.seymourbutts.com) can resolve faster than NS Record changes because they are controlled at the host level, not the Registrar. (Some hosts delay DNS updates.)

Because it’s new, no cache exists for it, so it will fetch a “live” record sooner.

DNS Caching

Because so many different things cache DNS, you may be able to see a DNS change before the client can - or vice versa.

If DNS is not resolving properly for anyone within 8 hours, say something. It doesn’t usually take that long and something could be wrong.

Any questions?