Description of 464xlat in Android
TL;DR - The Arris SB6183 cable modem is dropping IPv6 TCP traffic with the timestamp TCP option. See the "Workarounds" section for possible workarounds. 13 months later (October 2016), my modem was updated to D30CM-OSPREY-220.127.116.11-GA-01-NOSH. IPv6 tests show this problem is fixed with this firmware. The
I threw together some hardware I had on hand to make a PC-based router. IPv4 Getting IPv4 working was easy, I just needed to set ZONE=external and ZONE=trusted on the wan/lan interface ifcfg-* files. I threw net.ipv4.ip_forward=1 in /etc/sysctl.conf as well.