SERVER IS NOT RESPONDING or IS NOT CONSIDERED SUITABLE ......................... ad2008R2 failed test Advertising

Hi,

I have 2 DCs. One is dc2003 running windows server 2003 sp2 and all of operation masters are running in it. Another one is dc2008R2 running windows server 2008 R2. After I run dcdiag.exe in dc2008R2, this error occures:

Testing server: Default-First-Site-Name\ad2008R2
      Starting test: Advertising
         Warning: DsGetDcName returned information for\\ad2003.domain.local, when
         we were trying to reach ad2008R2.
         SERVER IS NOT RESPONDING or IS NOT CONSIDERED SUITABLE.
         ......................... ad2008R2 failed test Advertising

How can I solve this problem?