Netware 6.5 sp3-Symantec antivirus Corporate edition 9.0

If I use only the 2 Externals DNS on my server (configured in inetcfg) the
download def file with the FTP doesn't work.

If I add in the Hostname file, the adress of Symantec ftp it's good.

If i use only my 2 externals DNS on the Windows 2003 or XP for to do FTP,
it's good.

On my serveur the DNS is configured like in this adresse:

Why the ftp doesn't work on my Netware server and on Microsoft Windows, it's
Where is the problem, please?

And it's not possible to use all the days the hostname file because Symantec
change his IP adress all the days.

Sorry for my level english :-)