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DNS Record Crash Course for Web Developers

Chris Achard on October 29, 2019

This was originally posted as a twitter thread: https://twitter.com/chrisachard/status/1188870256971915265 Confused by DNS Records? A, CNAME, ALIA...
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David Paine20

Chris, awesome post. Thanks for sharing. There is a tool that I want to suggest here
dnschecker.org/all-dns-records-of-...
The reader, who wants to check the DNS record. they can check it here, from the above mention link.

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Giuseppe Caruso

Chris, awesome post, straight to the point. 🙌🏼

Can I suggest an edit?
It would be great, by using different colors, or just pointing it out, what is shown in your browser, and what is served.

E.G if I use a CNAME (does C stand for Canonical? 🤔) redirecting www.example.com to example.com, you can make it clearer with colors that the host www typed into the address bar will be shown in place of the domain without it, which, in turn, will show the actual content on the server.

TYPE            HOST    URL (in browser)         DOMAIN (served)
======================================================================
A Record        @       example.com        ->    104.198.14.52
----------------------------------------------------------------------
CNAME Record    www     www.example.com    ->    example.com
----------------------------------------------------------------------
CNAME Record    blog    blog.example.com   ->    example.herokudns.com
======================================================================
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That way, it's easier to understand that:

URL IN BROWSER                                ACTUAL CONTENT SERVED
======================================================================
www.example.com    ->    example.com    ->    104.198.14.52
======================================================================
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And, again, thanks for the super useful wrap-up!

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Chris Achard

This is a great way to visualize/explain it. Thanks!

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Nhlanhla Hasane • Edited

Hi Chris, i recently finished developing my portfolio using Angular8, and then yesterday i did register for a domain with netlify which costed about $16.99
after registration it did gave me those option to setup the A , CNAME, AAA records but i was still busy with some functionality of my portfolio. So i'd just brushed it off that i will do all that set up once i am done fixing the error on the IDE. So now i've deployed my site, the site is live but got an error when i clicked on its link' error : "Page not found, Looks like you've followed a broken link or entered a URL that doesn't exist on this site. " '

I have reached to out to support, its been almost 5 hours without any response

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Ben Halpern

Maybe a post in the help tag could help get you to the bottom of this?

#help

A place to ask questions and provide answers. We're here to work things out together.
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Nhlanhla Hasane

Thank you will do so. Ben

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Chris Achard

Hm; I haven't actually bought a domain through netlify before (I buy them outside of netlify and setup DNS separately), so I'm not 100% sure what might be happening, but I have a few ideas:

  1. Can you access the site directly with the "your-app.netlify.com" address? (if not, then it's not deployed correctly, so changing DNS stuff won't do anything)

  2. Can you access the domain part of netlify and check to see if the domain is "Verified"? (it turns green with no warning symbol)

  3. If the dns records are there and the site is working directly, it's possible it's a DNS cache issue - though 5 hours is usually enough in my experience for it to clear and fix itself, so that doesn't sound like it...

Does that help at all?

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Nhlanhla Hasane

The thing is i developed the site using vscode and then push my commits to its repo on github, and i fetched from github to netlify. Which deployed without any error. "My-app.netflify.com" is the one that's giving me the "Page Not Found Looks like you've followed a broken link or entered a URL that doesn't exist on this site." error and when i used my registered domain it want to DNS configuration. " to set up https. It's rollcoaster ride to be honest/

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Chris Achard

ah, if the direct netlify link doesn't work, then it's not a DNS issue - something went wrong with deploying your site. Under "deploys", make sure there is at least one successful build, and then click that link directly to see if it's working.

Hope you can figure it out! (sorry, can't help much if it's a deploy issue... keep trying/waiting for netlify support I suppose).

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Nhlanhla Hasane

Here's a repo for the site github.com/NhlanhlaHasane/Nhlanhla...

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Talz Cloning

Hi Chris,

Thanks for this. Actually for #5 you can do this at root level without breaking DNS specification dates from 1987. Cloudflare introduced CNAME Flattening feature, very useful if you’ve looking for a way to make your root domain work on a hosted service like AWS and Heroku.

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Chris Achard

Is that what they call a "virtual" CNAME, or something else? I think I read about that, but thought it was a different option (on Cloudflare) than just a normal CNAME? (could be wrong though - I haven't setup Cloudflare before)

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Talz Cloning

a CNAME as an A record, explanation over here CNAME Flattening

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Steeve

Thanks for this article, I didn't know about the CNAME limitation and the use of ALIAS to solve the problem. Good post Chris 🥂

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ادريس م

Just ensure that your DNS provider supports ALIAS as a resource record type, as it isn't defined by the official RFCs which govern the behaviour of the DNS.

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Chris Achard

Yes, definitely - different DNS providers have different workarounds.

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Chris Achard

Thanks!

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Peter Tyldesley

Amazing thanks. DNS has always been a pretty mysterious topic for me, so this was very helpful!

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Nick Spinazze

This is really interesting! Thanks for sharing. I think a cool follow up post might be digging into the history of DNS and why it was created in this fashion.

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Bernardo Gomes

Cool crash course ! Thanks for shared this!