How to preempt rogue RAs?

Michael Sinatra michael at
Sat Oct 30 21:17:43 CEST 2010

On 10/30/10 02:31, Martin Millnert wrote:
> Hi Tore,
> On Sat, October 30, 2010 10:53 am, Tore Anderson wrote:
>> Hi list,
>> (We suspect they
>> are running Windows Internet Connection Sharing but aren't quite sure.
>> Any insight here would be very welcome.)  These rogue RAs gets picked up
>> by all the other clients and cause trouble, especially for Mac OS X
>> users as they prefer the defective 6to4 connectivity over the proper
>> IPv4 one.
> A very ingenious tactic to handle the Windows ICS disaster is simply to
> set the preference of the proper announcements higher than normal.  This
> allegedly makes at least Windows prefer the higher preference
> announcements over others, especially the ICS because they go out as
> normal.  (Hint for MS; why not announce ICS RAs with lowest possible
> preference?)
> I have a patched quagga/zebra lying around somewhere, maybe i could make a
> patch out of it some day...

Whoops, this message got threaded in a way that caused me to miss it on 
my client, but this is basically what I suggested.  I know that cisco 
now supports this feature because I use it on UC Berkeley's wireless 
nets and it actually works.

There is no question that a device doing ad-hoc ICS should be announcing 
RAs at preference "low."  It's crazy that they implemented it with the 
default "medium" but perhaps that was based on their interpretation of 
RFC 4191.


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