As part of our IPv6 deployment we had to upgrade the firmware on our CPEs. We have a small variety of different models, but the majority of them are based on a Broadcom chipset. This firmware upgrade included all the features we needed for IPv6, the DHCPv6 client for the WAN, RA announcements on the LAN etc, but it also included other non-related IPv6 fixes and enhancements.
We spend a lot of time and effort regression testing these firmware pushes, and are generally pretty confident in it by the time we go to mass push it out via TR69. However, shortly after the firmware upgrade we started hearing complaints that this firmware had broken a very specific use case that we hadn’t obviously tested for.
IPv6 tunnels such as the 6in4 ones offered for free by Hurricane Electric. Odd, we hadn’t started the enablement of native IPv6 prefixes for these customers yet, but we did deploy it with ULA RAs enabled, could that be affecting things? We didn’t think so, but we had to investigate obviously.
6in4 tunnel client configured behind the router, inside the DMZ (not firewalled).
6in4 tunnel server on the internet, provided by Hurricane Electric.
Tunnel establishes correctly. Client gets an IPv6 prefix, can ping6 tunnel end-point as well as other v6 connected servers on the internet.
However, TCP sessions don’t establish over the tunnel.