Wietse Venema: > Greg A. Woods: > > There _should_ be one PTR for every _valid_ hostname using a given IP > > address. > > Statements such as above remind me of silly knights fighting windmills. > > There is a difference between "right" and "useful", and it even > depends on where they are used - server or client side. > > Multiple server A records are useful. More in the case of HTTP, > less in the case of SMTP which uses indirection via MX records. > (For a discussion about domain-in-a-box applications, see some > actual measurements that I did earlier this year). > > One PTR per A record is not useful. The server end will not know > what client name to use.
That is, one PTR per A record, in the case of multiple A records for the same IP address. > On the other hand, it is right when every PTR record has a matching > A record that resolves to (among others) the PTR record's address. > > Wietse > >
