Active directory authentication using ldap

Question

iam working in asp.net 1.1. my active directory dominname is ajcserver.
when i call ldap://ajcserver "server is not operational" error is showing. But i can call  ldap://196.1.1.253. it is working fine. but my requirement is ldap://domainname. my testing server is local server.how can i check it?? plese help me