Pro Tools connecting to S3 surface or E3 engine?

I've recently upgraded my S3L system to the latest software version ( and the hardware RAM upgrade ). The manual says Pro Tools gets connected to VENUE via one of E3 engine's network ports. I've previously connected Pro Tools from the S3 surface, not the Engine. Then how would you go about connecting Pro Tools in a sharing configuration - 2x S3L systems where all three network ports on the E3 engine are taken - one to connect the S3 surface, one to connect to the Stage box and one to connect to the other Engine in the system. The graphic diagram shows Pro Tools connecting to the S3 surface on either of these systems. Or it doesn't matter whether Pro Tools connects to S3 surface or E3 engine?