Re: OS trying to use IPv6 even though it's unavailable
Re: OS trying to use IPv6 even though it's unavailable
- Subject: Re: OS trying to use IPv6 even though it's unavailable
- From: Josh Graessley <email@hidden>
- Date: Tue, 17 Feb 2009 10:19:38 -0800
On Feb 17, 2009, at 9:37 AM, Jens Alfke wrote:
Now I'd like to know what caused this.
Should I be getting IPv6 responses from DNS queries at all?
Yes and no. At the DNS level, you will get IPv6 answers to AAAA and
Any record queries. I believe the DNS resolver library usually won't
ask for AAAA records unless it thinks the system has a routable IPv6
address assigned.
What causes the kernel to decide that IPv6 addresses are reachable,
since in this case it's wrong?
The kernel considers something reachable if it has a route. If
something on your network is advertising an IPv6 network (using
routing advertisements instead of DHCP), your system will self assign
an IPv6 address in the range advertised and use the advertised route.
The kernel doesn't decide whether the connection is IPv4 or IPv6,
applications and the frameworks they use make that call.
It's also possible to use something called 6to4. 6to4 will tunnel IPv6
on top of IPv4. It generates an IPv6 range based on your IPv4 address.
This only works for non-private addresses (if you aren't behind a NAT).
And why are the packets being dropped?
To figure that out, you need to determine where your IPv6 address was
coming from.
-josh
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