"Len Kutz" writes:

> Is it possible to have a DNS server configured to not work with DNS
> servers that don't support EDNS?

Not that I know of. RFC 2671 does not mention such a configuration (neither
to describe nor prohibit it), and no nameserver implementation of which I'm
aware (either BIND or other) has a configuration knob that could have this
result. I hope that these conditions are permanent -- pre-EDNS0 servers are
useful members of society and I think they should never become deprecated.
Paul Vixie