dns replies differ in src IP from query's dst IP (Bug?)

[Guy Pazi]

Hi,
I’ve seen the following paragraph in rfc 1035:
“- Some name servers send their responses from different addresses than the
one used to receive the query.  That is, a resolver cannot rely that a
response will come from the same address, which it sent the corresponding
query to. This name server bug is typically encountered in UNIX systems.”

I couldn’t find which NSs’ implementations enable this kind of behavior, and
if this is user configurable.
I’m interested in the behavior of popular NSs’ implementations (bind and
others).

P.S. whoever knows about this “bug”: is the IP used to reply dns queries is
typically used for listening to queries as well? I.e. does the resolver
issuing the query is aware of the IP used for reply as an additional IP of
the NS in question?
Thanks
Guy