One thing to note: we've discovered that on some common DSL routers, the
internal DNS caching server is on by default and answers requests on the
outside IP address. IIRC some even do it when configured for NAT.
So, even when you disable outside recursion, things you may not think of
on the inside of your network may still allow outside DNS recursion.
Efficient Networks DSL routers suffer from this problem if DNS servers are
defined in the DHCP server config on the router. It's more of a DNS proxy
though. It doesn't do any caching.
