I have a RUTX12 as main main router. It has dual SIM cards, one from EE and one from Vodafone. The EE SIM supports IPv4 and IPv6 and obtains an IP address 2a01:4c8:468:xxxx:xxxx:xxxx:xxxx:xxxx/64 reliably. The LAN shows an IP address 2a01:4c8:468:XXXX::1/64 which looks like it derives from the EE SIM. A PC connected to the LAN gets allocated an IPv6 address of 2a01:4c8:468:9d5d::821(Preferred) so it looks as if that is all working. However if the PC attempts to connect to any IPv6 external address, it looks like there is no route.
The PC IPv6 default gateway is fe80::21e:42ff:fe36:a521%12 and the router has an IPv6 address of inet6 fe80::21e:42ff:fe36:a521/64 scope link.
The router routing table for IPv6 looks like:
default from 2a01:4c8:468:9d5d::/64 via fe80::d83e:1ee1:9df4:e02b dev qmimux8 proto static metric 512 pref medium
2a01:4c8:468:9d5d::/64 dev br-lan proto static metric 1 pref medium
unreachable 2a01:4c8:468:9d5d::/64 dev lo proto static metric 2147483647 error 4294967183 pref medium
fd76:1731:c0c3::/64 dev br-lan proto static metric 1 pref medium
unreachable fd76:1731:c0c3::/48 dev lo proto static metric 2147483647 error 4294967183 pref medium
fe80::/64 dev br-lan proto kernel metric 256 pref medium
fe80::/64 dev wwan1 proto kernel metric 256 pref medium
fe80::/64 dev qmimux9 proto kernel metric 256 pref medium
fe80::/64 dev wwan0 proto kernel metric 256 pref medium
fe80::/64 dev qmimux8 proto kernel metric 256 pref medium
fe80::/64 dev tun0 proto kernel metric 256 pref medium
local ::1 dev lo table local proto kernel metric 0 pref medium
anycast 2a01:4c8:468:9d5d:: dev qmimux8 table local proto kernel metric 0 pref medium
anycast 2a01:4c8:468:9d5d:: dev br-lan table local proto kernel metric 0 pref medium
local 2a01:4c8:468:9d5d::1 dev br-lan table local proto kernel metric 0 pref medium
local 2a01:4c8:468:9d5d:439d:4d52:3e83:f338 dev qmimux8 table local proto kernel metric 0 pref medium
anycast fd76:1731:c0c3:: dev br-lan table local proto kernel metric 0 pref medium
local fd76:1731:c0c3::1 dev br-lan table local proto kernel metric 0 pref medium
anycast fe80:: dev br-lan table local proto kernel metric 0 pref medium
anycast fe80:: dev wwan1 table local proto kernel metric 0 pref medium
anycast fe80:: dev qmimux9 table local proto kernel metric 0 pref medium
anycast fe80:: dev wwan0 table local proto kernel metric 0 pref medium
anycast fe80:: dev qmimux8 table local proto kernel metric 0 pref medium
anycast fe80:: dev tun0 table local proto kernel metric 0 pref medium
local fe80::21e:42ff:fe36:a521 dev br-lan table local proto kernel metric 0 pref medium
local fe80::1410:366c:bc0f:9ee9 dev qmimux9 table local proto kernel metric 0 pref medium
local fe80::439d:4d52:3e83:f338 dev qmimux8 table local proto kernel metric 0 pref medium
local fe80::4942:5957:4ef6:7dd6 dev wwan0 table local proto kernel metric 0 pref medium
local fe80::4a45:77ec:50c:e01c dev wwan1 table local proto kernel metric 0 pref medium
local fe80::a51e:adf9:71af:b0dc dev tun0 table local proto kernel metric 0 pref medium
ff00::/8 dev br-lan table local proto kernel metric 256 pref medium
ff00::/8 dev wwan1 table local proto kernel metric 256 pref medium
ff00::/8 dev qmimux9 table local proto kernel metric 256 pref medium
ff00::/8 dev wwan0 table local proto kernel metric 256 pref medium
ff00::/8 dev qmimux8 table local proto kernel metric 256 pref medium
ff00::/8 dev tun0 table local proto kernel metric 256 pref medium
But I am still unable to connect from the PC to any external IP address.
If I ping Google IPv6 DNS from the Router it works:
PING 2001:4860:4860::8888 (2001:4860:4860::8888): 56 data bytes
64 bytes from 2001:4860:4860::8888: seq=0 ttl=114 time=25.627 ms
64 bytes from 2001:4860:4860::8888: seq=1 ttl=114 time=23.778 ms
64 bytes from 2001:4860:4860::8888: seq=2 ttl=114 time=27.551 ms
64 bytes from 2001:4860:4860::8888: seq=3 ttl=114 time=23.555 ms
64 bytes from 2001:4860:4860::8888: seq=4 ttl=114 time=23.430 ms
--- 2001:4860:4860::8888 ping statistics ---
5 packets transmitted, 5 packets received, 0% packet loss
round-trip min/avg/max = 23.430/24.788/27.551 ms
But not from the PC:
Pinging 2001:4860:4860::8888 with 32 bytes of data:
Destination net unreachable.
Destination net unreachable.
Destination net unreachable.
My guess is there is a route or firewall rule missing in the Router, but only a guess.