Teradata recommends that you restrict the netmask to limit traffic to high-speed networks only. For example, if the source and target systems are in the same 39.64.8.x BYNET network, a netmask of 255.255.255.0 will make sure there is communication from the remote IP to the BAR NC over the high bandwidth BYNET network. While a netmask of 0.0.0.0 does work, traffic over any of the network interfaces is allowed, such as going through a low-bandwidth 10.25.22.x LAN network, which may not be desirable.
The logical netmask defines the communication between the BAR NC and the remote Teradata systems by determining which network interface the remote database uses for data transfer to BAR NC.
If you are using an external DSC and the source or target Teradata system is configured to use a network fabric, the Data Mover media server (clienthandler) information must be configured to the fabric rather than the logical netmask. For more information, see Network Fabric for Systems.