I need to start migrating to a new domain (DNS/BIND)

[rmcc4444 at gmail.com]

i currently have a dns server that resolves about 500 hosts in
domain1.com. i need to now work towards migrating all current records
to domain2.com. over the next year or so, i will also need to keep
these domains in sync. ie: serverA.domain1.com has the same ip address
as serverA.domain2.com.

what is the best way to handle this? DNAME records??

thanks..