I don't believe you're looking for the answer to depend on the source IP address, which is what's normally known as a "view", or "split DNS".
If I understand you correctly, you want to serve the answer '1.2.3.4' if the question is Google, and '2.3.4.5' if the question is anything else.
For a BIND answer, see this question setting the wildcard to your '2.3.4.5' and just add specific records to override the wildcard for those domains that you want to resolve to '1.2.3.4'.
Alternatively, my evldns software could easily do this.
I don't know about NSD, but with BIND9's
view
clause you could create a view matching only Google's IP addresses.DNS for Rocket Scientists contain a section covering them: DNS BIND view Clause.
I don't believe you're looking for the answer to depend on the source IP address, which is what's normally known as a "view", or "split DNS".
If I understand you correctly, you want to serve the answer '1.2.3.4' if the question is Google, and '2.3.4.5' if the question is anything else.
For a BIND answer, see this question setting the wildcard to your '2.3.4.5' and just add specific records to override the wildcard for those domains that you want to resolve to '1.2.3.4'.
Alternatively, my evldns software could easily do this.