ARPA entries for a host with multiple IPs

[Sam Wilson]

In article <go4umg$1ksr$1 at sf1.isc.org>,
 Barry Margolin <barmar at alum.mit.edu> wrote:

> A common practice is to create unique names for each machine, in 
> addition to the round-robin entry.  This way, if you need to perform 
> maintenance on a specific machine, you can go to it by its unique name.  
> Then you should make the PTR record point to this name.  E.g. the 
> forward zone for myzone.com would contain:
> 
> ws IN A 1.2.3.1
>    IN A 1.2.3.2
>    IN A 1.2.3.3
> 
> ws-1 IN A 1.2.3.1
> ws-2 IN A 1.2.3.2
> ws-3 IN A 1.2.3.3
> 
> and the reverse zone 3.2.1.in-addr.arpa would contain:
> 
> 1 IN PTR ws-1.myzone.com.
> 2 IN PTR ws-2.myzone.com.
> 3 IN PTR ws-3.myzone.com.

Or it might contain

1 IN PTR ws.myzone.com.
2 IN PTR ws.myzone.com.
3 IN PTR ws.myzone.com.

Either is acceptable, but you have to decide which is more useful in 
your situation - is it more important to know which interface is being 
used to make an outgoing call (the usual use of PTR records) or is it 
vital the machine be recognised as the same one no matter which 
interface it uses?

You can try doing this:

1 IN PTR ws.myzone.com.
1 IN PTR ws-1.myzone.com.
2 IN PTR ws.myzone.com.
2 IN PTR ws-2.myzone.com.
3 IN PTR ws.myzone.com.
3 IN PTR ws-3.myzone.com.

which is technically legal but (allegedly) not many systems can make 
sensible use of multiple reverse entries and it might cause more 
confusion than it's worth.

Sam