UDP multicast packets not seen on listening interface in BETA5

Josh Carroll josh.carroll at gmail.com
Thu Sep 29 21:24:23 PDT 2005

> Running tcpdump, unless you use the -p flag, will put the NIC into
> promiscuous mode. This means you'll pick up all multicast frames
> (and everything else) regardless of how the NIC's multicast filter is
> programmed.

> Just joining a group will not put the interface into promiscuous mode:
> it'll just program the NIC's multicast filter to accept that particular
> group. That is of course unless someone a) broke the driver for your
> NIC or b) broke SIOCADDMULTI support somewhere in the stack. Until you
> tell us what NIC you have, there's no easy way to tell which is the
> case.

Ok, tcpdump without -p shows the multicast packets, tcpdump with -p
does not. Does that mean I have not joined the multicast group
properly? Is this something that was fixed sometime after BETA3? This
was working for a while in 5.4-RELEASE as well as since 6.0-BETA1.


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