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From: Anand Buddhdev <anandb@ripe.net>
Newsgroups: comp.protocols.dns.bind
Subject: Re: Dumb Question is an A or AAAA record required?
Date: Thu, 9 Jul 2020 14:43:04 +0200
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On 09/07/2020 14:21, @lbutlr wrote:

> Given a domain that is hosted and used for email and web, is an A
> record for that domain actually required?

It's not *required*. But see below.

> That is, if bob.tld is hosted by example.com can you simply have
> 
> 	NS ns1.example.com
> 	NS ns2.example.com
> 	MX mx.example.com
> 
> www	CNAME www.example.com
> 
> Without specifying
> 
> 	A 11.22.33.444

These days, many folk try to reach websites by typing just the bare 
domain name without the "www" prefix.

If a user types "bob.tld" into a browser, the browser will issue an 
address lookup for "bob.tld", causing the resolver to ask for A and AAAA 
records for "bob.tld". If you don't have an A record at the zone apex, 
the browser will not get back any address and display an error message 
for the user. An alert user might try "www.bob.tld" but most users are 
likely to just give up.

So while it's not *required* to have an address record at the apex, it's 
good practice to have one.

Anand