My Question:

Does anybody know if it's possible to make multiple concurrent PPPOE connections (from two parallel routers) to Spark UFB via a single NTU?

Background detail:

1. I have a Linksys 1900ACS router running DD-WRT. It is happily connected to Spark using PPOE via the Chorus provided UFB NTU.

2. I'm tinkering with (learning about) OPNSense on a multi NIC PC which I currently have connected downstream from the Linksys router.  ie.

Internet --> Spark (PPPOE) --> Linksys (10.x.x.x) --> OPNsense (192.168.x.x)

3. My wife is working from home and I can't afford to impact the Internet connection while I'm tinkering so I need to leave the Linksys in place until I can confirm that my implementation of OPNsense is solid. To achieve this I want to temporarily run both routers in parallel: i.e. 

Internet --> Spark (PPPOE) --> Linksys (10.x.x.x)

                                        --> OPNsense (192.168.x.x)

4. To avoid the complications of attempting to use multiple ports on the Chorus NTU I've introduced an unmanaged switch between the NTU and the Linksys router. This is to allow me to plug in the OPNsense box in parallel to the Linksys router. I've tested and confirmed that the Linksys router is continuing to connect to the internet with the switch in place. So far so good!

5. I've had a first attempt at connecting OPNSense in parallel to the Linksys router without success. I'm unclear is this is because Spark does not allow multiple PPOE connections through a single NTU or if it's just that I haven't got my OPNsense WAN config quite right yet.

6. I'm hoping that other people on the forum may have experience with what I'm attempting to do.