Forked from a lot of hard work done by Ben Grewell - Here: https://gist.github.com/bgrewell/faee67342085fb8fe98b446feeb10ced
This document has been updated based on setting this up for Centurylink 6RD IPv6
Run these commands from your UDM via SSH to obtain your IPv6 delegated prefix information for Centurylink:
LOCAL_IPv4=/sbin/ip route get 205.171.2.64 | awk -F"src " 'NR==1{split($2,a," ");print a[1]}'