After wasting 2 weeks on getting this to work I thought I would post a step-by-step guide.
I have been using iscsi targets on Oracle Solaris for years, but only with the installation of a new storage system with two VLANS (multipathed) for failover I needed Solaris to recognise the different VLANs in case of a interface failure.
This wasn't easy, since the Oracle Solaris documentation is very unclear about it. It has all the information there but finding it and understanding it is near impossible.
The following steps show you the procedure to connect and a single iscsi target accessible via two interfaces for failover.