Red Hat Bugzilla – Bug 10689
Multicast doesn't work unless promisc or allmulti is on
Last modified: 2008-05-01 11:37:55 EDT
I'm using 6.0 and a Xircom PCMCIA ethernet card (xirc2ps_cs).
MULTICAST is enabled (so says ifconfig)
However, I can't receive multicast packets unless the interface is switched
to PROMISC or ALLMULTI. I do see that the multicast group was joined (via
/proc/net/igmp), but no packets arrive.
As it turns out this may not be a bug - it is definitely a behavior difference
between the 2.0.x and 2.2.x kernel though. In 2.0.x you are permitted to create
a socket, join a group, and then bind the socket to the multicast address you
are interested in. In 2.2.x, you must bind first, and then join the group.
Argh. Scratch that. It still will not work under 2.2.x, but works beautifully
in all possible ways under 2.0.x.
I have now verified this behavior with several ethernet cards using different
I've tracked down the problem further. It only happens with a PCMCIA ethernet
card. A regular ethernet card works fine. The behavior happens with both
pcmcia-cs 3.1.10 and 3.1.14
This is a kernel problem. Changing component.
Does this still occur with 3.1.18