Disable multicast/IGMP

[jlh]

As a result of using tshark, I noticed that one of my machines keeps sending out UDP packets to 239.255.67.250:16680 every 30 minutes, without getting replies. From all the googling I did so far, this is a multicast IP address and this might be related to IGMP. I've seen some examples of what multicast is good for, but this doesn't explain why my computer wants to do some.

1) Why does the machine keep sending these packets and of what use are they?
2) How can I disable it?

It wouldn't normally bother me, but for now it pollutes my tshark capture files. I know that I could simply disable it in the kernel, but I prefer not doing that.

Thanks.

[jlh]

Mmh, seems I've been posting this too quickly and mixed two things. What I mentioned above is probably not IGMP, but it's still some multicast stuff. Additionally, I get IGMP packets too, which I wonder about just the same. Here's what I'm talking about:

2007-06-03 14:42:32.208719 192.168.100.1 -> 239.255.67.250 UDP Source port: 56102 Destination port: 16680
2007-06-03 15:12:32.202319 192.168.100.1 -> 239.255.67.250 UDP Source port: 56102 Destination port: 16680
2007-06-03 15:42:32.231822 192.168.100.1 -> 239.255.67.250 UDP Source port: 56102 Destination port: 16680
2007-06-03 16:12:32.258139 192.168.100.1 -> 239.255.67.250 UDP Source port: 56102 Destination port: 16680
2007-06-03 16:19:08.414460 192.168.100.1 -> 239.255.67.250 UDP Source port: 56102 Destination port: 16680
2007-06-03 16:42:32.278900 192.168.100.1 -> 239.255.67.250 UDP Source port: 56102 Destination port: 16680
2007-06-03 17:12:32.308832 192.168.100.1 -> 239.255.67.250 UDP Source port: 56102 Destination port: 16680
2007-06-03 17:42:32.285230 192.168.100.1 -> 239.255.67.250 UDP Source port: 56102 Destination port: 16680
2007-06-03 18:12:32.307538 192.168.100.1 -> 239.255.67.250 UDP Source port: 56102 Destination port: 16680
2007-06-03 18:42:33.543611 192.168.100.1 -> 239.255.67.250 UDP Source port: 56102 Destination port: 16680
2007-06-03 19:12:33.561528 192.168.100.1 -> 239.255.67.250 UDP Source port: 56102 Destination port: 16680
2007-06-03 19:42:33.575834 192.168.100.1 -> 239.255.67.250 UDP Source port: 56102 Destination port: 16680
2007-06-03 20:12:33.579937 192.168.100.1 -> 239.255.67.250 UDP Source port: 56102 Destination port: 16680
2007-06-03 20:39:49.659176 192.168.100.1 -> 239.255.67.250 UDP Source port: 56102 Destination port: 16680
2007-06-03 20:39:52.706920 192.168.100.1 -> 224.0.0.22 IGMP V3 Membership Report
2007-06-03 20:39:55.111820 192.168.100.1 -> 224.0.0.22 IGMP V3 Membership Report
2007-06-03 20:41:27.327660 192.168.100.1 -> 224.0.0.22 IGMP V3 Membership Report
2007-06-03 20:41:33.396439 192.168.100.1 -> 224.0.0.22 IGMP V3 Membership Report
2007-06-03 20:41:44.236669 192.168.100.1 -> 239.255.67.250 UDP Source port: 58713 Destination port: 16680
2007-06-03 21:11:27.466993 192.168.100.1 -> 239.255.67.250 UDP Source port: 58713 Destination port: 16680
2007-06-03 21:41:27.463160 192.168.100.1 -> 239.255.67.250 UDP Source port: 58713 Destination port: 16680

[mudrii]

check /etc/sysctl.conf
You will find ICMP broad cast desaible option that can help I think.
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www.gentoo.ro

[jlh]

Uhm, I was talking about IGMP, not ICMP. I don't have anything IGMP related in my /etc/sysctl.conf.