Re: Broken IPv6 / IPv4 configuration, or Gmail brokenness?
On Tue, 24 Jan 2023 18:41:56 +0000 (GMT)
Tim Woodall <debianuser@woodall.me.uk> wrote:
> On Mon, 23 Jan 2023, Celejar wrote:
>
> > Thank you - the plot thickens. I tried radvdump, and I was indeed
> > receiving IPv6 advertisements. I inspected my router (an OpenWrt box)
> > more carefully, and lo and behold, the router *thinks* that it has IPv6
> > connectivity: it reports that it has configured its WAN interface via
> > DHCPv6, that it has an IPv6 prefix delegation (a /56), and that it has
> > accordingly handed out an IPv6 address via DHCPv6 to my Debian system
> > (which indeed shows having its network interface configured with that
> > address). The problem is that IPv6 is not actually working at all:
> > ping6 to IPv6 hosts, even from the router itself, get no response, and
> > traceroute to IPv6 hosts show replies from only the first two hops, and
> > just asterisks afterward.
> >
> > My ISP is notoriously cagey about the details of its (slow and
> > incremental) IPv6 rollout. I suppose I can try customer service, but in
> > the meantime, I just don't know whether I have a misconfiguration on the
> > router, or whether the ISP is not actually providing working IPv6.
> >
>
> Does ping/traceroute work in ipv4?
Yes - pinging the same hosts that don't work using IPv6 works with ping
-4, and traceroute works with IPv4 addresses as well (I get some
asterisks, but many / most of the hops, including the destinations,
respond).
> It's depressingly common to find people who block icmp for 'security
> reasons'. While you can mostly get away with that in ipv4, ipv6 breaks
> catastrophically without at least some working icmp.
>
> Also try tcptraceroute - although if some router is configured to drop
> all icmp then I don't think ipv6 can work at all
tcptraceroute work fine. tcptraceroute6 gives the same problem as
regular traceroute6 - all asterisks after the first couple of hops.
--
Celejar
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