Disabling Authentication on one nic

How can I disable a dos network boot disk client from trying to authticate to a servers that doesn’t have Netbios bound to the nic thats on a particular network. Senerio. Backup network, only on BDC has netbios bound so dos boot disks can map a drive. But other BDC’s on backup net attempt to authenticate but apparently can’t because there is no netbios there. Can I disable the servers advertizing their authentication services or can I tell the dos diskette which server to authenticate to?
Thanks,
Bill Connell