[dns-operations] CNAME points to itself

John Levine johnl at taugh.com
Tue Jul 5 21:30:48 UTC 2016

>I have found that CNAME can be setup to point to itself (at least in 
>BIND9 it can be).
>www.itest.com.          300     IN      CNAME   www.itest.com.
>should this be disabled?

There's no point.  How would you prevent this?

 --- (on your nameserver) ---

 www.foo.com. 300 IN CNAME www.bar.com.

 --- (on another nameserver on the other side of the planet) ---

 www.bar.com. 300 IN CNAME www.foo.com.

As others have noted, you have to break CNAME loops when you resolve
names.  You can't prevent them.

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