RE: 6to4 tunnel trouble
We have had the same thing on expensive switches, something to note is in our experience they are the same switches that PPPoE won't work through.
-----Original Message-----
From: Jeroen Massar [mailto:jeroen@unfix.org]
Sent: Tuesday, 23 December 2008 3:04 a.m.
To: Pascal Hambourg
Cc: debian-ipv6@lists.debian.org
Subject: Re: 6to4 tunnel trouble
Pascal Hambourg wrote:
> Jeroen Massar a écrit :
>> Martin List-Petersen wrote:
>> [..]
>>> your switches are layer2, tcp/ip (be it v4 or v6) goes on top of
>>> that and your switches wouldn't know the difference.
>>
>> Unfortunately that is not really the case. Especially when it comes
>> to handling multicast there are certain (not many though) switches
>> that do not properly handle multicast, as such all IPv6 Neighbor
>> Discovery goes bad. Sometimes it does work at one point and then
>> fails at another. This happened to several 'expensive' switches and also to cheap ones.
>
> Don't cheap "dumb" switches to handle multicast as broadcast ?
That is one solution, and in that case multicast could work.
The but here is that some switches only handle a subset of the MAC addresses which are meant for multicast purposes and as IPv6 uses a different range than the standard set, some of these setups break.
>> Generally putting an interface in PROMISC handles the problem
>> partially, but that is something one wants to avoid of course.
>
> I knew about the promisc trick as a workaround with broken ethernet
> NICs or drivers, but how could it help when the switch is broken ?
It helped in some cases I have encountered, don't know exactly why though; replacing the hardware in question is generally the best solution depending on what one wants to achieve.
Greets,
Jeroen
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