Do we ever want to bind more than 8 multicast MAC addresses?
ypod at mit.edu
Fri Apr 18 12:01:27 EDT 2008
David Woodhouse wrote:
> On Fri, 2008-04-18 at 11:50 -0400, Polychronis Ypodimatopoulos wrote:
>> what's possible? why not?
>> David Woodhouse wrote:
>>> On Fri, 2008-04-18 at 11:43 -0400, Polychronis Ypodimatopoulos wrote:
>>>> Is it possible to associate shared activities with ethernet ports
>>>> instead of whole multicast addresses? Then we would only need one single
>>>> multicast address and do the filtering on the ethernet ports (eg IP is
>>>> port 0x0800). At the very least, the multicast address is 6 bytes and
>>>> the ethernet port is 2 bytes.
>>> That's possible, yes -- although you won't get the device filtering it
>>> for you then.
> Error. Question upside down. Please don't top-post.
> It's possible to do as you say -- to use different ports for different
> activities (although I read 'UDP ports' where you actually said
> 'ethernet ports' so perhaps I misunderstood).
> The device firmware doesn't speak IPv6 or Legacy IP, however -- and we
> wouldn't want it to, even if we trusted it. So it wouldn't filter for
> only those ports you're interested in; it'll give you all packets for
> that address.
You're not following: Ethernet ports are bytes 12-14 (2 bytes total) on
_all_ ethernet frames. IP has nothing to do with this. Instead of
looking at the first 6 bytes (destination mac) for a specific multicast
address, the filter should be looking at bytes 12-14 for a specific
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