i see these both have ip bus wires but there is only one ip bus input in the d3 what is the deal with this

Daisy chain them, thats why they have an in and out

The cables are color-coded to where they plug in on the CBT-200 and D3. Blue end of the IP bus cable (out) from the GEX-P10XMT plugs into the CBT-200; then plug the black end of the IP cable that came with the CBT-200 into it and plug the other (blue) end into the D3 - all set.