MicrosoftShouldn't the site name modifications be done in the *trusted* forest ? After all, it's here where the client's DNS requests, containing _ldap._tcp_.<trustingForestSite>._sites.dc_msdcs_.<trustedForestName>, will eventually land. Modifying the sites in the trusting forest will not achieve the objective, since the DNS servers in the trusting forest cannot answer queries ending in ...<trustedForestName>, but can only forward them to the DNS servers in the trusted forest, based on the stub zone/conditional forwarders/etc.
