Código:
<membership defaultProvider="AspNetActiveDirectoryMembershipProvider">
<providers>
<add name="AspNetActiveDirectoryMembershipProvider"
type="System.Web.Security.ActiveDirectoryMembershipProvider, System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"
connectionStringName="LDAP://servidor/OU=UsuariosWeb,DC=servidor,DC=local"
connectionUsername="USUARIO"
connectionPassword="PASSWORD"/>
</providers>
</membership>

