Normally the 2240 HA pair will be in an "active-active" configuration. I'm not sure what you are reading, but I would recommend that you read the following:
Configuration Examples for FAS2240 Systems - https://library.netapp.com/ecm/ecm_get_file/ECMP1139842
Data Ontap 8.1 Software Setup Guide (7-mode) - https://library.netapp.com/ecm/ecm_get_file/ECMP1119529
and for more in-depth info, read the following:
Data Ontap 8.1 Network Management Guide (7-mode) - https://library.netapp.com/ecm/ecm_get_file/ECMP1114171
Data Ontap 8.1 System Administration Guide (7-mode) - https://library.netapp.com/ecm/ecm_get_file/ECMP1136573 (or the appropriate one for your Ontap version)
The NetApp onsite engineer who comes in to install your hardware will normally configure the network interfaces for you if you supply them with the needed information (ip addresses, etc.)