CNAME and IPv6

[Marco Moock]

Am 28.05.2024 um 12:00:09 Uhr schrieb Peter:

>   if I understand corrently, the use of CNAME is just a convenience
> and no technical feature, right?

It is technical because the query is redirected to the domain listed in
the CNAME.

> In lots of examples on the net, a zonefile for a domain might contain
> things similar to this:
> 
>   @ORIGIN example.com.
>   ..
>   myhost 	       A	1.2.3.4
>   www	       	       CNAME	myhost.example.com.
>   www1	       	       CNAME	myhost.example.com.
>   someapp	       CNAME	myhost.example.com.
>   xyz	       	       CNAME	myhost.example.com.
>   ...

That all points to this node, e.g. because multiple services are
running on the same machines, but it should be possible to separate
them when needed without changing domain names on other machines that
need to access them.
When the IP address changes, only the records of the machine listed in
CNAME need to be changed at one place.

> Often, the webserver and other applications are not actually
> running on node 1.2.3.4, but are internally portforwarded to
> some other node, for various reasons.

This is bad IPv4 stuff, you should get rid off that ASAP.
Use CNAMEs for each node that exists in reality and point to it with
CNAME.



> Now we add an IPv6 address for 'myhost'. But portforwarding
> doesn't work for IPv6. Instead we are required to use different
> addresses all over, like so:

port forwarding would work, but is nasty here. Redirectors like rinetd
can handle that, but I recommend against in this case.

> So, how would you do it? Is there a nice and elegant way?

www	CNAME	webserver1
ftp	CNAME	ftp2

webserver1	A	192.168.0.1
webserver1	AAAA	2001:db8::1
ftp2		A	172.16.0.1
ftp2		AAAA	2001:db8:9999::1

That makes it possible to redirect it to the actual machines that runs
the service.

-- 
Gruß
Marco

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