Hello Ivan,  VNXe is extremely different than most storage arrays in terms of how it handles iSCSI. There is no LUN trespassing on VNXe.  Classically, the best practice is to use 2 IP interfaces for an iSCSI initiator that would connect to the 2 IP interfaces for the iSCSI target (one to one). For the same iSCSI server, one iSCSI target IP would be made to use eth2, while the other IP would use eth3. So, this way we achieve 2 independent paths to make IOs to the LUNs. Now depending on the path selection policy implemented at host end, paths can be used as 'both active', or 'one active and other standby'.  Note: Different OS have different recommendations for path selection.
In VNXe 3100 box if we configure iSCSI server on SP A using eth 2 and eth 3 and same on SP B using eth2 and eth 3, so will it automatically load balance the data traffic between eth 2 and eth 3 of SP A if all my luns are provisioned using ISCSI server on SP A or will it still use the eth 2 of SP A for primary transfer and if there is any fault with eth 2 then only trespass it to eth 3 for the data traffic. 
Load Balancing between eth2 and eth3 on SP A using iSCSI server on VNXe.