Logging into Novell 6.0 via IP not IPX

We are experiencing problems with our computers logging into the Novell 6.0 servers under IPX instead of IP. The prefered protocol on the workstations is IP. Sometimes the machines log in with IP but mostly with IPX. How can I force them to all log in with IP all the time? We still need to run IPX due to some applications though. Thank you!