Can't reach web UI via pi.hole (but IP works)—help me debug?

So it's come down to two things:

  1. The ServerIP environment variable has to be set on the pihole docker container. (It should be set to the LAN IP of the machine that the container is running on.)
  2. Even with this fix, the router's DNS is intercepting the request to pi.hole. That is, if I set /etc/resolv.conf to use the pihole box directly, http://pi.hole resolves fine. But if I set it to the router's IP, and configure the router to use the pihole box as the DNS, then it fails. So, at this point, it looks like a DD-WRT issue, and I'll go ask on their forums.

Considering this issue fixed. Thanks again for the insight!