[Olsr-users] Route-Flapping | Out of Control [Deutsch]

Roar Bjørgum Rotvik (spam-protected)
Tue Dec 28 22:53:39 CET 2010

Den 23.12.2010 11:14, skrev Markus Kittenberger:
> On Thu, Dec 23, 2010 at 9:16 PM, Michael Rack
> <(spam-protected)
> <mailto:(spam-protected)>> wrote:
>      > OLSR packets are sent over multicast.  In IEEE 802.11, unicast and
>      > multicast packets use different link-layer protocols, and it's fairly
>      > usual to see much higher loss rates for multicast than for unicast
>      > packets.
>     OLSR packets are set via broadcast, not multicast ;)
>     multicast is a routed subnet via IGMP in range -
> routet or not, or which iprange, makes no difference at layers < 3
> regarding ethernet layer 2 any mac adress having the last bit of the
> first byte set to 1 is a multicast,..
> this includes broadcasts FF:FF:FF:FF:FF:FF or various types of multicasts,..

That is not correct as far as I know, broadcast traffic is not 
iterpreted as multicast just because the last bit of first byte is 1.

See http://en.wikipedia.org/wiki/Multicast_address

The ethernet destination with this value is interpreted as IPV4 mcast:
01-00-5E-xx-xx-xx 	0x0800 	IPv4 Multicast (RFC 1112)

So the first 3 bytes in ethernet destination must be "01-00-5E", not 
only last bit of first byte for the packet to be interpreted as mcast.

Roar Bjørgum Rotvik

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