Running IPv6 on a large L2 network

Mohacsi Janos mohacsi at
Sun Sep 14 22:30:31 CEST 2008

On Sun, 14 Sep 2008, Leen Besselink wrote:

> On Tue, Sep 09, 2008 at 11:53:51AM +0100, Tim Chown wrote:
>> On Tue, Sep 09, 2008 at 12:43:04PM +0200, G?ran Weinholt wrote:
>>> weinholt at (G?ran Weinholt) writes:
>>>> In the scenario I posted it doesn't matter if I disconnect the user
>>>> that sent the RA, the network will still be broken for other hosts
>>>> because of the bogus on-link route. To remove the route I might send
>>>> my own RA with the announced prefixes and a very low lifetime, but the
>>>> lowest lifetime allowed according to RFC4862 is two hours (ironically
>>>> changed recently to address a possible DoS...)
>>> Ok, I did some tests and both Linux and Windows Vista will actually
>>> honor a AdvValidLifetime and AdvPreferredLifetime of zero. So now I
>>> just have to write a program that counteracts bad RAs and everything
>>> should be fine.
>>> Thanks for the other suggestions in this thread, but if we could
>>> afford to upgrade to a routed network (with one VLAN per customer or
>>> what have you) we would. :)
>> I'm about to do a revision of this draft:
>> so any feedback is timely.
>> We also have a modified rafixd that I'll see if we can put up somewhere
>> for people to fetch/use if they wish.
> I sometimes read this list when I have time. And that started me thinking and then
> usually things go bad. So tell me if I'm stupid.
> What if we, the kind of early adaptors of IPv6 compiled a list of 'possible bad packets'
> and send it to the switch vendors so they can add a filter for them.
> I really hate workarounds and yes, I don't mind a workaround when I need it
> 'now, now, now'. But I do want to know the workaround can go away eventually.
> I know we'll be buying more switches eventually, updating firmware, removing old, etc.
> So why not make life easier ?
> I mean if you have an advanced switch it can already look at your IPv4-header
> and prioritize based on TCP/IP port-number and what not.
> Also I hear IPv6 has a 'fixed header' to make it easy for route vendors
> to route, but that also means it's easier for switch vendors to filter, right ?
> Is there anyone on this list who has good connections with there switch-vendors ?
> So, I suggest adding these on the list first:
> - RA, a per port setting (or for a very simple switch, just the 
> uplink-port ?)

proposal exists for more than a year now. Just vendor has to implement.

Janos Mohacsi
Network Engineer, Research Associate, Head of Network Planning and Projects
Key 70EF9882: DEC2 C685 1ED4 C95A 145F  4300 6F64 7B00 70EF 9882

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