The Name Resolution Policy Table (NRPT) is a very cool new feature available in Windows 7. The NRPT allows for a type of conditional DNS routing based on the name that needs to be resolved. Entries on the NRPT can contain domain names, sub-domains, or even individual host names. You can then assign custom DNS servers for each of these entries.
The DirectAccess client leverages this feature to enable an efficient split DNS name resolution methodology. For all names contained on the corpnet, the DA client sends its requests to DNS servers on the corporate network. For all names not on the corporate network, the DA client sends the requests to the DNS servers configured on its network interface.
Tom Shinder in his Edge Man blog goes over some of the details of how the NRPT works over at:
DEBRA LITTLEJOHN SHINDER
MVP (Enterprise Security)