First of all, kudos to Comcast for trying to roll out IPv6 across their entire network. Static IPv6 netblocks seem to be available for Comcast business users, and IPv6 is enabled unconditionally in the CPE routers used by Comcast business class internet. Unfortunately, the software in the two available CPE routers (SMC & Cisco) is horribly broken when it comes to IPv6. The TL;DR summary: even when IPv6 firewalling is disabled in the configuration, the router still tracks every IPv6 "connection", which causes every single DNS lookup to fill up a slot in its connection tracking table. The router's logs say it blocks tens of thousands of IPv6 connections every day, despite firewalling being "disabled" on the router. Once the connection tracking table fills up, both IPv6 and IPv4 start having trouble, with packet loss on ICMP, high ping times to the local router (and the internet), and new connections not establishing. The router randomly crashes and reboots too, sometimes multiple times a day. This ends up breaking both IPv6 and IPv4. It only takes about 300kbit/s of DNS traffic to trigger the bug, in both the SMC and the Cisco routers. Are there any Comcast NOC or other technical people present who could help? I am interested both in helping resolve the firmware issues in the routers (there will no doubt be other customers who hit this in the future, as IPv6 becomes ore common) or, if that is not an option, finding some way to avoid the issue. http://forums.businesshelp.comcast.com/t5/Equipment-Modems-Gateways/Cis co-DPC3941B-slows-to-a-crawl-and-crashes-several-times-a-day/td-p/30807 -- All Rights Reversed.