IPv6 networking functional outbound, but inbound traffic is lost
We have a prefix deligation, it is 2603:3026:138::/56
Our Barracuda F80 router has four ports. port 4 is connected to the Comcast Gateway (cable modem).
The F80's configuration assigns a static IP address to port 4 of 2603:3026:138::1. The F80 also has the default gateway (::/0) address the same as the Ipv6 address of the Cable Modem's interface ( 2603:3026:138::80b2:34ff:fe4a:37b3)
Internet-------> Cable Modem--->CM Interface--->CM Switch<----F80 Port4<----F80 Router
The Barracuda F80 is able to ping such addresses as 2001:4860:4860::8888 and it gets a reply.
However, if I go to a web site such as https://www.subnetonline.com/pages/ipv6-network-tools/online-ipv6-ping.php and try to ping my F80's port 4 IP address, I don't get a reply
If I ping the Cable Modem's IP address (the really long one above), I get a reply
If I login to the Cable Modem and use the troubleshooting tools and ping the IP address of port 4 of the router, that works just fine as well.
Apparently, the cable modem is having trouble routing packets destined for the 2603:3026:138::/56 network to port 4 of my router (2603:3026:138::1).
I suspect it needs to know that 2603:3026:138::1 is the gateway for the 2603:3026:138::/56 network and for some reason it isn't realizing this. It is almost as if the Comcast Modem isn't doing IPV6 autoconfiguration correctly or something....or perhaps my router is at fault.
I just got off the phone with tech support and the nice lady had me put our Cable modem into Psedo Bridge mode. However, there is no routing information on how to route packets onto Comcast's network in this configuration, and I am therefore unable to make it work.
It also broke IPv4 routing as well. So I am not sure Psedo Bridge mode is the answer.
How do I resolve this?