Reverse address entries

Sam Wilson Sam.Wilson at
Tue Jul 16 09:04:43 UTC 2013

In article <mailman.807.1373643569.20661.bind-users at>,
 "Novosielski, Ryan" <novosirj at> wrote:

> Came across another instance where [reverse lookups] may matter: TCP Wrappers.
> Although the case there was a bit more peculiar -- does not
> appear to have FORWARD DNS for at least some of its dynamic address
> space. So you can get a PTR, and then address validation fails on the
> forward address. I guess perhaps if you had no PTR it would never go
> that far.

Yep, when you have PTRs they should agree with the A records or paranoid 
reverse lookup will fail.  That should still be fairly quick, though, 
since there should be NXDOMAIN responses to the forward lookups rather 
than timeouts.


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