push apps failing in Android until you disable IPv6

[Ted Mittelstaedt]

That is correct, Tim

When you define an interface in Cisco IOS as IPv6 enabled but you don't
assign a prefix, all you get is LL assignments from it.  I don't think
that IOS version 12 has any notion of ULA addresses in IPv6.

Keep in mind that I only tested IPv6 assignment, not reachability.
I wanted to see if it was possible to configure the router to
assign just LL and advertise a DG and Android would pick it up.

I wonder if you assign an IPv6 DNS server, LL addressing, and
advertise a DG, would Android ignore RFC 6724 and attempt to reach
the IPv6 DNS servers before attempting to reach the IPv4 DNS servers?

Ted

On 5/9/2016 6:48 AM, Tim Chown wrote:
>> On 9 May 2016, at 10:17, Tore Anderson<tore at fud.no>  wrote:
>>
>> * Erik Kline<ek at google.com>
>>
>>> If this router were to send out an RA advertising itself as a default
>>> router in this configuration that would probably cause the symptoms
>>> you're seeing.  That's why I asked for a sample of any RAs seen on
>>> such a network.  (Such a configuration would of course be broken,
>>> effectively requiring Happy Eyeballs to function at all.)
>>
>> Assuming the source address selection is implemented in a sane way,
>> just having a an IPv6 default router doesn't on its own explain the
>> symptoms described. IPv4 should be preferred due to the Android device's
>> link-local address not having the same scope as the IPv6 address of the
>> web site or whatever. See RFC6724 sections 5 and 6, rule 2.
>>
>> The RA would have to additionally contain a PIO with global scope, as I
>> understand it. Then you'd certainly get in trouble (disregarding Happy
>> Eyeballs). Even a ULA PIO could be problematic if Android's source
>> address selection algorithm isn't updated to RFC6724 defaults. RFC3484
>> predates ULAs, so it treats them the same as other globally scoped
>> addresses.
>
> This was one of the reasons for the RFC 6724 update, and would fit the symptoms being described were the device using older heuristics, but it sounds like the device has only LL and not ULA, right Ted?
>
> Tim
>