@taylorjayne or your ISP uses CG-NAT, that is essentially the same as an additional NAT router.

My ISP uses CG-NAT and I pay the 5 bucks a month for a fixed IP that bypasses the CG-NAT.

  @taylorjayne 

another view can be : 

Stop using IPv4 and switch to IPv6 where there's no NAT.

And use IPv6's prefix delegation on your system between routers as it is a really basic function of IPv6..

Note : don't use multiple IPv6 address as you're entitled to because Deco's firmware finds it very difficult to manage (Yes, really ! It is easy to be locked in your own fd00::/8 network without any exit). Just keep your stuff on your external IP (the 2000::/3 network) and manage the exposure through your firewall..