TIL of what happens when you put a random url in your DNS records
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So when you use a A record, it points to the IP address.
The "A" stands for "address" and this is the most fundamental type of DNS record: it indicates the IP address of a given domain. For example, if you pull the DNS records of cloudflare.com, the A record currently returns an IP address of: 104.17.210.9.
A records only hold IPv4 addresses. If a website has an IPv6 address, it will instead use an "AAAA" record.
via Cloudflare
But you can't just shove any URL in there.
For example:
example.com's IP address is 93.184.216.34 (which you can find using dig +short example.com
Name: bad-ip
Type: A
Target: 93.184.216.34
TTL: 60
This would assume your site bad-ip.website-example.com would point to example.com, right?
NAH! It'll 404!
Why?
When your browser requests a website, it sends a Host header with the name of the domain you typed in. If the server (like Apache/nginx) doesn't recognize that name, it'll often return a 404. Here's more detail about how that works.
When you request example.com and everything works, here's what happens:
- Type
example.cominto your browser - Browser asks: where's
example.com? - Resolver responds: 93.184.216.34
- Browser (to 93.184.216.34): an HTTP request for Host:
example.com! - Example.com server: I know that site! Here's a response!
But when you request bad-ip.shark98.messwithdns.com and you get a 404, here's how it goes:
-
Type example.com into your browser
-
Browser asks: where's
bad-ip.website-example.com? -
Resolver responds: 93.184.216.34
-
(everything is the same so far!)
-
Browser (to 93.184.216.34): an HTTP request for Host:
bad-ip.website-example.com! -
Example.com server: I've never heard of that site!! 404!
I learned about this on this sweet DNS sandbox https://messwithdns.net/
I hope this site still works. I saw things changing from even a year ago.
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Tagged: dns