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by o11c 876 days ago
That doesn't work any more than anything else.

I'm testing with `ping ipv6.google.com` as well as the router IPs. Between each change, I disconnect from wifi.

The router itself has a ping tool and can ping ipv6.google.com just fine. So I assume the upstream options are correct.

For the LAN, I have 4 options:

* ND Proxy gives me an fd/8 address. I can ping the router via its fd/8 or fe80 address, google blackholes.

* DHCPv6 gives me an ::/64 address. I can ping the router via its fd/8 or ::/64 addresses, google blackholes

* SLAAC + Stateless DHCP does not give me any address (I still have the default fe80 address). I can ping the router via its fd/8 or ::/64 addresses, google gives Destination unreachable: Beyond scope of source address

* SLAAC + RDNSS does not give me any address (I still have the default fe80 address). I can ping the router via its fd/8 or ::/64 addresses, google gives Destination unreachable: Beyond scope of source address

In all cases, the IPv6 addresses the router says are its DNS servers blackhole. I do have working DNS returning IPv6 address for google though; presumably because the ipv4 DNS server it advertises (which is the router itself) still works.

If I bypass the wifi router, the ISP router gives me both an address in both fd/8 (in the same /64 as the wifi router gets assigned, which makes sense) and in 2607/16, besides the usual fe80. The ISP router is really bad, all it has is an "it's connected" indicator and a bunch of phone numbers and URLs for support.

Still bypassing, pinging `ip6-allnodes` gives me 3 responses, all with fe80::/64 addresses: my computer, an unknown, and the wifi router; I can ping those addresses, as well as the wifi router's fd/8 address.

Maybe I should play with the router's upstream settings ... "Get IPv6 address" has auto, slaac, dhcpv6, non-address ... since I can ping it from outside that has to be right. If I disable "Prefix delegation" the ::/64 box is editable but it complains about literally anything entered. And I don't have anything meaningful to manually enter a DNS address.

Hm, I just noticed that the last bit of the router's address varies between some of its addresses ...

1 comments

fd::/8 addresses (really fc00::/7) are ULA addresses [0], defined as non-routable local addresses, so it’s expected that you can’t get out to the internet through just that address.

Do you have any smart home devices? Protocols like Thread and HomeKit establish their own randomly-generated ULA prefixes and advertise them through RA’s (router advertisements) and correctly-configured devices in your LAN will observe the RA for that network and generate a local address for it (including your router.) So just seeing a fd/8 address doesn’t mean your actual router gave you it, it just means that something on your network is using a ULA prefix.

Basically, it’s possible the real problem is that you’re not actually seeing an RA from a “real” (routable) IPv6 subnet when behind your router.

> If I bypass the wifi router, the ISP router gives me both an address in both fd/8 (in the same /64 as the wifi router gets assigned, which makes sense) and in 2607/16, besides the usual fe80

When you do this, can you ping out? (`ping6 2607:f8b0:4004:c17::65` or something to rule out DNS issues.)

> Maybe I should play with the router's upstream settings ... "Get IPv6 address" has auto, slaac, dhcpv6, non-address ... since I can ping it from outside that has to be right. If I disable "Prefix delegation" the ::/64 box is editable but it complains about literally anything entered. And I don't have anything meaningful to manually enter a DNS address

What you want here is dhcpv6 and prefix delegation. This will make your router ask the ISP for a real IPv6 network to use, and upon receiving this from your ISP, will send RA’s out to your local network for a “real” (2607/16 or whatever) network. A prefix length of 64 should do it, unless you need multiple subnets inside your router. (People say dhcpv6 is obsolete by SLAAC, but prefix delegation is a different thing… if you want to have your own router obtain a network prefix from an ISP, DHCPv6+PD is the only way to do this.)

- [0] https://en.wikipedia.org/wiki/Unique_local_address