Only 6to4 addresses are accessible via 6to4 interface

I have a configured 6to4 interface. I can communicate with any other 6to4 host (2002::/4), but not with other hosts, packets just seem dropped. I've tried several configurations and OSes so I think this is a provider issue. How can I make sure it is it and what should I tell my provider?

UPD: the routing table, it is identical to one from a machine which works perfectly.

::192.88.99.1 dev 6to4  metric 1024  mtu 1480 advmss 1420 hoplimit 0
::/96 via :: dev 6to4  metric 256  mtu 1440 advmss 1380 hoplimit 0
2002::/16 dev 6to4  proto kernel  metric 256  mtu 1440 advmss 1380 hoplimit 0
fe80::/64 dev 6to4  proto kernel  metric 256  mtu 1440 advmss 1380 hoplimit 0
fe80::/64 dev eth0  proto kernel  metric 256  mtu 1500 advmss 1440 hoplimit 0
fe80::/64 dev br0  proto kernel  metric 256  mtu 1500 advmss 1440 hoplimit 0
fe80::/64 dev wlan0  proto kernel  metric 256  mtu 1500 advmss 1440 hoplimit 0
default via ::192.88.99.1 dev 6to4  metric 1024  mtu 1440 advmss 1380 hoplimit 0

From serverfault wRAR

• Sounds like you don't have a relay set up to reach the native IPv6 Internet. You should be going to the global anycast address, 192.88.99.1, which various providers advertise. (Depending on where you are and your ISP's peering, the nearest visible relay might be on another continent.)

  The IPv6 format of that address is 2002:c058:6301:: so you probably just want to add that as the default route for IPv6 traffic.

  You don't mention your OS or provide your current configuration. So I'll give the "classic" ifconfig command:

  route add -inet6 default 2002:c058:6301::
  

  wRAR : I know about relay, though I've seen only ::192.88.99.1 in docs, not 2002:c058:6301:: (and 2002:c058:6301:: doesn't work either). I've added the routing table to the post.
  From Phil P

• It is a provider routing problem, 192.88.99.1 is not accessible, while, for example, 147.45.21.2 can be successfully used as a gateway.

  From wRAR