David Malone wrote:
On Tue, Mar 01, 2005 at 03:51:34PM +0200, Jari Arkko wrote:
On the other hand, if the problem is in bad drivers (as Bill points
out), this may be a different issue. I guess part of the problem
is that for plain old IPv4 usage multicast features in NICs and the
drivers don't get tested well, so you see problems when you
switch to IPv6 or other things that depend on multicast
capabilities. Is there any way to determine how widespread this
problem is?
I've seen this problem once or twice on FreeBSD, where the driver
author either didn't have enough information to program the multicast
filters or didn't complete the programming of the multicast filters
because it wasn't necessary for the normal opperation of IPv4. Mind
you, all such problems that I knew about have been fixed for some.
(The practical version of the promiscuous mode work-around for this
problem is to run "tcpdump -i blah" in the background on a problem
machine.)
I presume promisc and tcpdump is used on a wide scale to avoid this
problem. I for myself have used it very often on various wifi cards
Orinoco and Cisco.
For one, I don't think this is a proper way to assume that IPv6 works ok
over these cards. This [promisc] is something one can do in the lab on
some computer where one can type commands, or on cards that do support
this promisc. For two, putting the card in promisc mode and then saying
that multicast is beneficial because it offers scalability, less
processing power etc - is little appropriate.
Anyways, please do not get me wrong. It is not in my intentions to
heat any discussion or whatever. I just have a local problem whose only
solution was to send RAs to ff. Things may change with driver updates
and so on.
Alex
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