Practices (10)

Set up your DNS server with two views
"external"
authoritative-only server for your zone
do not allow recursion
accept queries from anyone
"internal"
caching-only server for local clients
restrict queries from local subnet only
check the behavior by sending queries
Set up two views for two authoritative zones
"external" and "internal" like the previous config
use the same domain name with different contents
set up secondary servers for both with your partner
check the behavior