This is one of the most confusing and disturbing threads I have read recently. While most of the information is "correct" the way it is stitched together is very confusing and sometimes misleading. But, I find this throughout D*'s technology right now.
D* uses TCP/IP for their MRV. Some of the early adopters used their existing home networks to implement this by directly connecting their home network connections directly into the internet connections on their receivers. It works, but D* does not support this setup. D* wants to use their coax network to carry the signals so they developed a box that would transfer the signal from the internet connector on their receiver to their coax. Thus was born the DECA. Think of it as a pipe that just transfers data from a twisted pair to coax, nothing more.
By the time they developed the H/HR24 series they decided to incorporate the DECA converter into the receiver so you did not have to have an external box with a separate twisted pair wire to your receiver. Great idea. The technology for MRV was now baked into the receiver. But, this brought some problems with people who plugged their internet signal into the HR24 only to see their MRV disappear. So there had to be a way to connect their coax network to your router. This came in the form of their new "Cinema Connection Kit". Now, by having two signals on the coax you had all your satellite service, MRV and video on demand running through your D* coax.
Along comes the HR34 and guess what; they decided to bake the Cinema Connection Kit into this receiver. And it seems that at this point all heck broke loose with installers and forum members understanding of the now dozens of configurations that would work. I find that everyone knows what works for their environments without understanding the uniqueness of the poster's environment. And most of the posts in this thread display that confusion.
Yes, you can use an external DECA/CCK with a system that includes an HR34. But, you only want to do this if it is clearly the best solution for the installation. This poster appears to have an easy ethernet connection to his HR34 and wonders why he has a CCK in the basement. I wonder the same thing. Apparently the installer saw the router there and just decided it was the easiest way to install it. Most installers are don't have the time to ask a lot of questions and sort of assume the customer can't give them a good answer anyway so they are going to do what makes the most sense to them. So, if I were waltah, I would remove the CCK downstairs and just plug the internet cable directly into the HR34. If he has problems, he can always reinstall the CCK. There is just one caveat; he needs to replace the terminator on the splitter when he removes the connection. I suspect the installer took it with him so waltah needs to go to Home Depot and get some more.
Just my thoughts.