Probably nothing interesting.

There are two 8-port ethernet switches.

With 12 nodes, this leaves 4 unused port (2 in each switch).

From the pictures you can see that the box itself has two jacks, both of which are likely connected to one switch each.

The switches don't seem to support link aggregation, so likely to look like this:

    switch1
    ├── external
    ├── nano-pi1
    ├── nano-pi2
    ├── nano-pi3
    ├── nano-pi4
    ├── nano-pi5
    └── nano-pi6
    switch2
    ├── external
    ├── nano-pi7
    ├── nano-pi8
    ├── nano-pi9
    ├── nano-pi10
    ├── nano-pi11
    └── nano-pi12

and if you connect both the switches to the same external switch, you'd get something like:

     switch1
    ┌┼── switch2
    │├── nano-pi1
    │├── nano-pi2
    │├── nano-pi3
    │├── nano-pi4
    │├── nano-pi5
    │└── nano-pi6
    │switch2
    └┼── switch1
     ├── nano-pi7
     ├── nano-pi8
     ├── nano-pi9
     ├── nano-pi10
     ├── nano-pi11
     └── nano-pi12